Updated on 2023/02/05

写真a

 
EJIRI Shinji
 
Organization
Academic Assembly Institute of Science and Technology Fundamental Sciences Associate Professor
Faculty of Science Department of Science Associate Professor
Title
Associate Professor
External link

Degree

  • Doctor (Science) ( 1996.3   Kanazawa University )

  • 理学修士 ( 1993.3   金沢大学 )

Research Areas

  • Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

Research History (researchmap)

  • Niigata University   Faculty of Science Department of Science   Associate Professor

    2017.4

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  • Niigata University   Faculty of Science Department of Physics Fundamental Physics   Associate Professor

    2014.4 - 2017.3

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  • Niigata University   Headquarters for Strategy and Planning Office for Promoting the Cultivation of Young Researchers   Associate Professor

    2010.1 - 2014.3

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  • Brookhaven National Laboratory   Physics Department   Associate Physicist

    2008.10 - 2010.1

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  • Brookhaven National Laboratory   Physics Department   Assistant Physicist

    2006.10 - 2008.9

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  • The University of Tokyo   Department of Physics   Research Assistant

    2005.2 - 2006.10

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  • University of Bielefeld   Department of Physics   Researcher

    2003.4 - 2005.1

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  • University of Wales Swansea   Department of Physics   Researcher

    2001.4 - 2003.3

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  • University of Tsukuba   Center for Computational Physics   Special researcher of the Japan Society for the Promotion of Science

    1998.4 - 2001.3

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  • University of Tsukuba   Center for Computational Physics   Researcher

    1997.4 - 1998.3

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Research History

  • Niigata University   Faculty of Science Department of Science   Associate Professor

    2017.4

  • Niigata University   Abolition organization Fundamental Physics   Associate Professor

    2014.4 - 2017.3

  • Niigata University   Headquarters for Strategy and Planning Office for Promoting the Cultivation of Young Researchers   Associate Professor

    2010.1 - 2014.3

Education

  • Kanazawa University   Graduate School, Division of Science and Technology

    1993.4 - 1996.3

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    Country: Japan

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  • Kanazawa University   Graduate School, Division of Natural Science   Physics Course

    1991.4 - 1993.3

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    Country: Japan

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  • Kanazawa University   Faculty of Science   Department of Physics

    1987.4 - 1991.3

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    Country: Japan

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Professional Memberships

Committee Memberships

  • 日本物理学会   素粒子論領域運営委員  

    2011.5 - 2012.3   

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    Committee type:Academic society

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Papers

  • Canonical partition function and center symmetry breaking in finite density lattice gauge theories Reviewed

    Shinji Ejiri

    Physical Review D   106 ( 11 )   114505   2022.12

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1103/PhysRevD.106.114505

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  • Latent heat and pressure gap at the first-order deconfining phase transition of SU(3) Yang-Mills theory using the small flow-time expansion method Reviewed

    Kazuyuki Kanaya, Mizuki Shirogane, Shinji Ejiri, Ryo Iwami, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)   LATTICE 2021   064   2022.7

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Sissa Medialab  

    DOI: 10.22323/1.396.0064

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  • Particle density probability distribution function and center symmetry breaking in finite density lattice gauge theories Reviewed

    Shinji Ejiri

    Proceedings of The 38th International Symposium on Lattice Field Theory — PoS(LATTICE2021)   LATTICE 2021   531   2022.7

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    DOI: 10.22323/1.396.0531

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  • Scope and convergence of the hopping parameter expansion in finite-temperature quantum chromodynamics with heavy quarks around the critical point Reviewed International journal

    Naoki Wakabayashi, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa

    Progress of Theoretical and Experimental Physics   2022 ( 3 )   033B05   2022.3

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    <title>Abstract</title>
    Hopping parameter expansion is a useful tool for investigating heavy dynamical quarks in lattice quantum chromodynamics (QCD), though its range of applicability has sometimes been questioned. We study the convergence and the valid range of the hopping parameter expansion in determining the critical point (critical quark mass) of QCD with heavy quarks at finite temperature and density. On lattices with sufficiently large spatial extent, the terms in the hopping parameter expansion are classified into Wilson loop terms and Polyakov-type loop terms. We first study the case of the worst convergence in which all the gauge link variables are unit matrices and thus the Wilson loops and the Polyakov-type loops get their maximum values. We perform explicit calculation up to more than the 100th order of the hopping parameter expansion. We show that the hopping parameter expansion is convergent up to the chiral limit of free Wilson quarks. We then perform a Monte Carlo simulation to measure correlation among Polyakov-type loop terms up to the 20th order of the hopping parameter expansion. In previous studies, strong correlation between the leading-order Polyakov loop term and the next-to-leading-order bent Polyakov loop terms was reported and used to construct an effective theory to incorporate the next-to-leading-order effect by a shift of the leading-order coupling parameter. We establish that the strong correlation among Polyakov-type loop terms also holds at higher orders of the hopping parameter expansion, and extend the effective theory to incorporate higher-order effects up to high orders. Using the effective theory, we study the truncation error of the hopping parameter expansion. We find that the previous next-to-leading-order result for the critical point for Nt = 4 is reliable. For Nt ≥ 6, we need to incorporate higher-order effects in the effective theory.

    DOI: 10.1093/ptep/ptac019

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    Other Link: https://academic.oup.com/ptep/article-pdf/2022/3/033B05/42829507/ptac019.pdf

  • Finite-size scaling around the critical point in the heavy quark region of QCD Reviewed

    Atsushi Kiyohara, Masakiyo Kitazawa, Shinji Ejiri, Kazuyuki Kanaya

    Physical Review D   104 ( 11 )   114509   2021.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society (APS)  

    DOI: 10.1103/physrevd.104.114509

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevD.104.114509/fulltext

  • Latent heat and pressure gap at the first-order deconfining phase transition of SU(3) Yang–Mills theory using the small flow-time expansion method Reviewed

    Mizuki Shirogane, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Progress of Theoretical and Experimental Physics   2021 ( 1 )   013B08   2021.1

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Oxford University Press (OUP)  

    <title>Abstract</title>
    We study latent heat and the pressure gap between the hot and cold phases at the first-order deconfining phase transition temperature of the SU(3) Yang–Mills theory. Performing simulations on lattices with various spatial volumes and lattice spacings, we calculate the gaps of the energy density and pressure using the small flow-time expansion (SF$t$X) method. We find that the latent heat $\Delta \epsilon$ in the continuum limit is $\Delta \epsilon /T^4 = 1.117 \pm 0.040$ for the aspect ratio $N_s/N_t=8$ and $1.349 \pm 0.038$ for $N_s/N_t=6$ at the transition temperature $T=T_c$. We also confirm that the pressure gap is consistent with zero, as expected from the dynamical balance of two phases at $T_c$. From hysteresis curves of the energy density near $T_c$, we show that the energy density in the (metastable) deconfined phase is sensitive to the spatial volume, while that in the confined phase is insensitive. Furthermore, we examine the effect of alternative procedures in the SF$t$X method—the order of the continuum and the vanishing flow-time extrapolations, and also the renormalization scale and higher-order corrections in the matching coefficients. We confirm that the final results are all very consistent with each other for these alternatives.

    DOI: 10.1093/ptep/ptaa184

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  • Erratum: Nf=2+1 QCD thermodynamics with gradient flow using two-loop matching coefficients (Physical Review D (2020) 102 (014510) DOI: 10.1103/PhysRevD.102.014510) Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda

    Physical Review D   102 ( 5 )   059903   2020.9

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    In Sec. II C, Eqs. (50) and (51) for “linear+log fit” should read (Farmula Presented) and (Farmula Presented) espectively, where ΛMS=332(17) MeV is the QCD lambda parameter for three-flavor QCD quoted in the Particle Data Group [1]. The dotted curves for the linear+log fit in Figs. 2–7, 10, and 12 were showing the results of nonlinear fit by error. The correct figures are given in this Erratum. The caption of Fig. 10 is slightly modified to quote Eq. (51). (Figure Presented) Analyses in the paper have been done adopting the above correct formulas, and thus the results and the tables as well as other figures are unchanged.

    DOI: 10.1103/PhysRevD.102.059903

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  • Determination of the endpoint of the first order deconfiniement phase transition in the heavy quark region of QCD Reviewed International journal

    Shinji Ejiri, Shota Itagaki, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Atsushi Kiyohara, Mizuki Shirogane, Yusuke Taniguchi, Takashi Umeda, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2019   071   2020.8

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    DOI: 10.22323/1.363.0071

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  • Calculation of PCAC mass with Wilson fermion using gradient flow Reviewed International journal

    Atsushi Baba, Asobu Suzuki, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of Science   LATTICE 2019   191   2020.8

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    We calculate the PCAC mass for (2 + 1) flavor full QCD with Wilson-type quarks. We adopt the Small Flow-time eXpansion (SFtX) method based on the gradient flow which provides us a general way to compute correctly renormalized observables even if the relevant symmetries for the observable are broken explicitly due to the lattice regularization, such as the Poincáre and chiral symmetries. Our calculation is performed on heavy u, d quarks mass (mπ /mρ ≃ 0.63) and approximately physical s quark mass with fine lattice a ≃ 0.07 fm. The results are compared with those computed with the Schrödinger functional method.

    DOI: 10.22323/1.363.0191

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  • Study of 2+1 flavor finite-temperature QCD using improved Wilson quarks at the physical point with the gradient flow Reviewed International journal

    Kazuyuki Kanaya, Atsushi Baba, Asobu Suzuki, Shinji Ejiri, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of Science   LATTICE 2019   088   2020.8

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    We study thermodynamic properties of 2 + 1 flavor QCD applying the Small Flow-time eXpansion (SFtX) method based on the gradient flow. The method provides us with a general way to compute correctly renormalized observables irrespective of explicit violation of symmetries due to the regularization, such as the Poincaré and chiral symmetries on the lattice. We report on the status of our on-going project to compute the energy-momentum tensor and the chiral condensate at the physical point with improved Wilson quarks, extending our previous study with slightly heavy u and d quarks. We also report on our test of two-loop matching coefficients recently calculated by Harlander et al., revisiting the case of QCD with slightly heavy u and d quarks. Our results suggest that the SFtX method is powerful in extracting physical observables on the lattice.

    DOI: 10.22323/1.363.0088

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  • Nf=2+1 QCD thermodynamics with gradient flow using two-loop matching coefficients Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda

    Physical Review D   102 ( 1 )   014510   2020.7

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    We study thermodynamic properties of N-f = 2 + 1 QCD on the lattice adopting a nonperturbatively Ooa+-improved Wilson quark action and the renormalization group-improved Iwasaki gauge action. To cope with the problems due to explicit violation of the Poincare and chiral symmetries, we apply the small flow-time expansion (SFtX) method based on the gradient flow, which is a general method to correctly calculate any renormalized observables on the lattice. In this method, the matching coefficients in front of operators in the small flow-time expansion are calculated by perturbation theory thanks to the asymptotic freedom around the small flow-time limit. In a previous study using one-loop matching coefficients, we found that the SFtX method works well for the equation of state extracted from diagonal components of the energy-momentum tensor and for the chiral condensates and susceptibilities. In this paper, we study the effect of two-loop matching coefficients which have been calculated by Harlander et al. recently. We also test the influence of the renormalization scale in the SFtX method. We find that, by adopting the mu(0) renormalization scale of Harlander et al. instead of the conventional mu(d) = 1/root 8t scale, the linear behavior at large flow-times is improved so that we can perform the t -> 0 extrapolation of the SFtX method more confidently. In the calculation of the two-loop matching coefficients by Harlander et al., the equation of motion for quark fields was used. For the entropy density in which the equation ofmotion has no effects, we find that the results using the two-loop coefficients agree well with those using one-loop coefficients. On the other hand, for the trace anomaly which is affected by the equation of motion, we find discrepancies between the one- and two-loop results at high temperatures. By comparing the results of one-loop coefficients with and without using the equation of motion, the main origin of the discrepancies is suggested to be attributed to contamination of O((aT)(2)) = O(1/N-t(2)) discretization errors in the equation of motion at N-t less than or similar to 10.

    DOI: 10.1103/physrevd.102.014510

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    Other Link: http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevD.102.014510/fulltext

  • End point of the first-order phase transition of QCD in the heavy quark region by reweighting from quenched QCD Reviewed

    Shinji Ejiri, Shota Itagaki, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Atsushi Kiyohara, Mizuki Shirogane, Takashi Umeda

    Physical Review D   101 ( 5 )   054505   2020.3

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    DOI: 10.1103/PhysRevD.101.054505

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  • Measuring of chiral susceptibility using gradient flow Reviewed

    Atsushi Baba, Asobu Suzuki, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Takanori Shimojo, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of Science   LATTICE2018   173   2019.5

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    © Copyright owned by the author(s) under the terms of the Creative Commons. In lattice QCD with Wilson-type quarks, the chiral symmetry is explicitly broken by the Wilson term on finite lattices. Though the symmetry is guaranteed to recover in the continuum limit, a series of non-trivial procedures are required to recover the correct renormalized theory in the continuum limit. Recently, a new use of the gradient flow technique was proposed, in which correctly renormalized quantities are evaluated in the vanishing flow-time limit. This enables us to directly study the chiral condensate and its susceptibility with Wilson-type quarks. Extending our previous study of the chiral condensate and its disconnected susceptibility in (2+1)-flavor QCD at a heavy u, d quark mass (mπ /mρ ≃ 0.63) and approximately physical s quark mass, we compute the connected contributions to the chiral susceptibility in the temperature range of 178–348 MeV on a fine lattice with a ≃ 0.07 fm.

    DOI: 10.22323/1.334.0173

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  • Study of energy-momentum tensor correlation function in Nf=2+1 full QCD for QGP viscosities Reviewed

    Yusuke Taniguchi, Atsushi Baba, Asobu Suzuki, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Takanori Shimojo, Hiroshi Suzuki, Takashi Umeda

    Proceedings of Science   LATTICE2018   166   2019.5

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    © Copyright owned by the author(s) under the terms of the Creative Commons. We study correlation functions of the energy-momentum tensor (EMT) in (2 + 1)-flavor full QCD to evaluate QGP viscosities. We adopt nonperturbatively improved Wilson fermion and Iwasaki gauge action. Our degenerate u, d quark mass is rather heavy with mπ /mρ ' 0.63, while the s quark mass is set to approximately its physical value. Performing simulations on lattices with Nt = 16 to 6 at a fine lattice spacing of a = 0.07 fm, the temperature range of T ' 174–464 MeV is covered using the fixed-scale approach. We attempt to compute viscosities by three steps: (1) calculate two point correlation functions of non-perturbatively renormalized EMT applying the gradient flow method, (2) derive the spectral function from correlation function, and (3) extract viscosities from the spectral function applying the Kubo formula. We report on the status of the project and present preliminary results for the shear viscosity in the high temperature phase.

    DOI: 10.22323/1.334.0166

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  • Equation of state near the first order phase transition point of SU(3) gauge theory using gradient flow Reviewed

    Mizuki Shirogane, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of Science   LATTICE2018   164   2019.5

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    © Copyright owned by the author(s) under the terms of the Creative Commons. We study energy gap (latent heat) between the hot and cold phases at the first order phase transition point of the SU(3) gauge theory. Performing simulations on lattices with various spatial volumes and lattice spacings, we calculate the energy gap by a method using the Yang-Mills gradient flow and compare it with that by the conventional derivative method.

    DOI: 10.22323/1.334.0164

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  • Erratum: Exploring Nf=2+1 QCD thermodynamics from the gradient flow (Physical Review D (2017) 96 (014509) DOI: 10.1103/PhysRevD.99.014509) Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda, Naoki Wakabayashi

    Physical Review D   99 ( 5 )   059904   2019.3

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    © 2019 authors. Published by the American Physical Society. Equation (C7) in the Appendix should read (Formula Presented) The wrong expression is not used in our numerical simulations and any results are not affected by this typo.

    DOI: 10.1103/PhysRevD.99.059904

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  • Equation of state in (2+1)-flavor QCD at physical point with improved Wilson fermion action using gradient flow Reviewed

    Kazuyuki Kanaya, Shinji Ejiri, Ryo Iwami, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    EPJ Web of Conferences   175 ( Lattice 2017 )   07023   2018.3

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    © The Authors, published by EDP Sciences, 2018. We study the energy-momentum tensor and the equation of state as well as the chiral condensate in (2+1)-flavor QCD at the physical point applying the method of Makino and Suzuki based on the gradient flow. We adopt a nonperturbatively O(a)- improved Wilson quark action and the renormalization group-improved Iwasaki gauge action. At Lattice 2016, we have presented our preliminary results of our study in (2+1)- flavor QCD at a heavy u; d quark mass point. We now extend the study to the physical point and perform finite-temperature simulations in the range T ? 155.544 MeV (Nt = 4-14 including odd Nt's) at a ? 0:09 fm. We show our final results of the heavy QCD study and present some preliminary results obtained at the physical point so far.

    DOI: 10.1051/epjconf/201817507023

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  • Energy-momentum tensor correlation function in Nf=2+1 full QCD at finite temperature Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Asobu Suzuki, Hiroshi Suzuki, Takashi Umeda

    EPJ Web of Conferences   175 ( Lattice 2017 )   07013   2018.3

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    We measure correlation functions of the nonperturbatively renormalized
    energy-momentum tensor in $N_f=2+1$ full QCD at finite temperature by applying
    the gradient flow method both to the gauge and quark fields. Our main interest
    is to study the conservation law of the energy-momentum tensor and to test
    whether the linear response relation is properly realized for the entropy
    density. By using the linear response relation we calculate the specific heat
    from the correlation function. We adopt the nonperturbatively improved Wilson
    fermion and Iwasaki gauge action at a fine lattice spacing $=0.07$ fm. In this
    paper the temperature is limited to a single value $T=232$ MeV. The $u$, $d$
    quark mass is rather heavy with $m_\pi/m_\rho=0.63$ while the $s$ quark mass is
    set to approximately its physical value.

    DOI: 10.1051/epjconf/201817507013

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  • O(4) scaling analysis in two-flavor QCD at finite temperature and density with improved Wilson quarks Reviewed

    T. Umeda, S. Ejiri, R. Iwami, K. Kanaya, H. Ohno, A. Uji, N. Wakabayashi, S. Yoshida

    Proceedings of Science   LATTICE 2016   376   2017.3

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    DOI: 10.22323/1.256.0376

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  • Equation of state in (2+1)-flavor QCD with gradient flow Reviewed

    Kazuyuki Kanaya, Shinji Ejiri, Ryo Iwami, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda, Naoki Wakabayashi

    Proceedings of Science   LATTICE2016   063   2017.3

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    © Copyright owned by the author(s). The energy-momentum tensor and equation of state are studied in finite-temperature (2+1)-flavor QCD with improved Wilson quarks using the method proposed by Makino and Suzuki based on the gradient flow. We find that the results of the gradient flow are consistent with the previous results using the T-integration method at T <∼ 280MeV (Nτ > ∼ 10), while a disagreement is found at T > ∼ 350MeV (Nτ < ∼ 8) presumably due to the small-Nτ lattice artifact. We also report on the results on the renormalized chiral condensate and its disconnected susceptibility using the method of Hieda and Suzuki. The results show a clear signal of the expected chiral restoration crossover even with Wilson-type quarks which violate the chiral symmetry explicitly.

    DOI: 10.22323/1.256.0063

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  • Temperature dependence of topological susceptibility using gradient flow Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda, Ryo Iwami, Naoki Wakabayashi

    Proceedings of Science   LATTICE2016   064   2017.3

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    © Copyright owned by the author(s). We study temperature dependence of the topological susceptibility with the Nf = 2+1 flavors Wilson fermion. We have two major interests in this paper. One is a comparison of gluonic and fermionic definitions of the topological susceptibility. Two definitions are related by the chiral Ward-Takahashi identity but their coincidence is highly non-trivial for the Wilson fermion. By applying the gradient flow both for the gauge and quark fields we find a good agreement of these two measurements. The other is a verification of a prediction of the dilute instanton gas approximation at low temperature region Tpc < T < 1.5Tpc, for which we confirm the prediction that the topological susceptibility decays with power χτ ∝ (T/Tpc)-8 for three flavors QCD.

    DOI: 10.22323/1.256.0064

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  • Determination of latent heat at the finite temperature phase transition of SU(3) gauge theory Reviewed

    Shinji Ejiri, Ryo Iwami, Mizuki Shirogane, Naoki Wakabayashi, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    Proceedings of Science   LATTICE2016   058   2017.3

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    © Copyright owned by the author(s). We calculate the energy gap (latent heat) and pressure gap between the hot and cold phases of the SU(3) gauge theory at the first order deconfining phase transition point. We perform simulations around the phase transition point with the lattice size in the temporal direction Nτ =6; 8 and 12 and extrapolate the results to the continuum limit. The energy density and pressure are evaluated by the derivative method with nonperturabative anisotropy coefficients. We find that the pressure gap vanishes at all values of Nt. The spatial volume dependence in the latent heat is found to be small on large lattices. Performing extrapolation to the continuum limit, we obtain Δϵ=T4 =0:75±0:17 and δ(ϵ -3p)=T4 = 0:623±0:056: We also tested a method using the Yang-Mills gradient flow. The preliminary results are consistent with those by the derivative method within the error.

    DOI: 10.22323/1.256.0058

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  • Critical point search from an extended parameter space of lattice QCD at finite temperature and density Reviewed

    Shinji Ejiri, Ryo Iwami, Norikazu Yamada

    NUCLEAR PHYSICS A   956   826 - 829   2016.10

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ELSEVIER SCIENCE BV  

    Aiming to understand the phase structure of lattice QCD at nonzero temperature and density, we study the phase transitions of QCD in an extended parameter space, where the number of flavor and quark masses are considered as parameters. Performing simulations of 2 flavor QCD and using the reweighting method, we investigate (2 + N-f) flavor QCD at finite density, where two light flavors and N-f massive flavors exist. Calculating probability distribution functions, we determine the critical surface terminating first order phase transitions in the parameter space of the light quark mass, the heavy quark mass and the chemical potential. Through the study of the many flavor system, we discuss the phase structure of QCD at finite density.

    DOI: 10.1016/j.nuclphysa.2016.01.030

    Web of Science

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  • Exploring Nf=2+1 QCD thermodynamics from the gradient flow Reviewed

    Yusuke Taniguchi, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Takashi Umeda, Naoki Wakabayashi

    Physical Review D   96 ( 1 )   014509   2016.9

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    The energy-momentum tensor plays an important role in QCD thermodynamics. Its
    expectation value contains information of the pressure and the energy density
    as its diagonal part. Further properties like viscosity and specific heat can
    be extracted from its correlation function. Recently a new method based on the
    gradient flow was introduced to calculate the energy-momentum tensor on the
    lattice, and has been successfully applied to quenched QCD.
    In this paper, we apply the gradient flow method to calculate the
    energy-momentum tensor in (2+1)-flavor QCD. As the first application of the
    method with dynamical quarks, we study at a single but fine lattice spacing
    a=0.07 fm with heavy u and d quarks ($m_\pi/m_\rho=0.63$) and approximately
    physical s quark. Performing simulations on lattices with Nt=16 to 4, the
    temperature range of T=174-697 MeV is covered. We find that the results of the
    pressure and the energy density by the gradient flow method are consistent with
    the previous results using the T-integration method at T<280 MeV, while the
    results show disagreement at T>350 MeV (Nt<8), presumably due to the small-Nt
    lattice artifact of $O((aT)^2)=O(1/N_t^2)$.
    We also apply the gradient flow method to evaluate the chiral condensate
    taking advantage of the gradient flow method that renormalized quantities can
    be directly computed avoiding the difficulty of explicit chiral violation with
    lattice quarks. We compute the renormalized chiral condensate in the MS-bar
    scheme at renormalization scale $\mu=2$ GeV with a high precision to study the
    temperature dependence of the chiral condensate and its disconnected
    susceptibility. Even with the Wilson-type quark action, we obtain the chiral
    condensate and its disconnected susceptibility showing a clear signal of
    pseudocritical temperature at T~190 MeV related to the chiral restoration
    crossover.

    DOI: 10.1103/PhysRevD.96.014509

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  • Importance of third moments of fluctuations of conserved charges in relativistic heavy-ion collisions Reviewed

    Masayuki Asakawa, Shinji Ejiri, Masakiyo Kitazawa

    EUROPEAN PHYSICAL JOURNAL A   52 ( 8 )   252   2016.8

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    We discuss the importance of third moments of conserved charges around their averages in relativistic heavy-ion collisions.

    DOI: 10.1140/epja/i2016-16252-5

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  • Latent heat at the first order phase transition point of SU(3) gauge theory Reviewed

    Mizuki Shirogane, Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa

    PHYSICAL REVIEW D   94 ( 1 )   014506   2016.7

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    We calculate the energy gap (latent heat) and pressure gap between the hot and cold phases of the SU(3) gauge theory at the first order deconfining phase transition point. We perform simulations around the phase transition point with the lattice size in the temporal direction N-t = 6, 8 and 12 and extrapolate the results to the continuum limit. We also investigate the spatial volume dependence. The energy density and pressure are evaluated by the derivative method with nonperturabative anisotropy coefficients. We adopt a multipoint reweighting method to determine the anisotropy coefficients. We confirm that the anisotropy coefficients approach the perturbative values as N-t increases. We find that the pressure gap vanishes at all values of N-t when the nonperturbative anisotropy coefficients are used. The spatial volume dependence in the latent heat is found to be small on large lattices. Performing extrapolation to the continuum limit, we obtain Delta epsilon/T-4 = 0.75 +/- 0.17 and Delta(epsilon - 3p)/T-4 = 0.623 +/- 0.056.

    DOI: 10.1103/PhysRevD.94.014506

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  • Many flavor approach to study the critical point in finite density QCD Reviewed

    Ryo Iwami, Shinji Ejiri, Norikazu Yamada

    Proceedings of Science   LATTICE 2015   146   2016.7

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    DOI: 10.22323/1.251.0146

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  • Analytic continuation of finite density QCD with heavy quarks in the strong coupling region Reviewed

    Shinji Ejiri, Hiroshi Yoneyama

    Proceedings of Science   LATTICE 2015   150   2016.7

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    DOI: 10.22323/1.251.0150

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  • Many flavor approach to study the nature of chiral phase transition of two-flavor QCD Reviewed

    Norikazu Yamada, Shinji Ejiri, Ryo Iwami

    Proceedings of Science   LATTICE 2015   147   2016.7

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    DOI: 10.22323/1.251.0147

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  • Towards the QCD equation of state at the physical point using Wilson fermion Reviewed

    T. Umeda, S. Ejiri, R. Iwami, K. Kanaya, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2015   209   2016.7

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    DOI: 10.22323/1.251.0209

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  • Exploring the nature of chiral phase transition in two-flavor QCD using extra heavy quarks Reviewed

    Shinji Ejiri, Ryo Iwami, Norikazu Yamada

    PHYSICAL REVIEW D   93 ( 5 )   054506   2016.3

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    Chiral phase transition of two-flavor QCD at finite quark masses is known to be a crossover except near the chiral limit, but it can turn to a first order transition when adding many extra flavors. This property is used to explore the nature of the phase transition of massless two-flavor QCD using lattice numerical simulations. The extra heavy flavors being incorporated in the form of the hopping parameter expansion through the reweighting, the number of the extra flavors and their masses appear only in a single parameter, defined by h. We determine the critical value of h, at which the first order and the crossover regions are separated, and examine its dependence on the two-flavor mass. The lattice calculations are carried out at N-t = 4, and show that the critical value of h does not depend on the two-flavor mass in the range we have studied (0.46 &lt;= m(pi)/m(rho) &lt;= 0.66) and appears to remain finite and positive in the chiral limit, suggesting that the phase transition of massless two-flavor QCD is of second order.

    DOI: 10.1103/PhysRevD.93.054506

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  • First order transition regions in the quark masses and chemical potential parameter space of QCD Reviewed

    Shinji Ejiri, Norikazu Yamada, Hiroshi Yoneyama

    Proceedings of Science   CPOD 2014   014   2015.11

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    DOI: 10.22323/1.217.0014

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  • Multipoint reweighting method and its applications to lattice QCD Reviewed

    R. Iwami, S. Ejiri, K. Kanaya, Y. Nakagawa, D. Yamamoto, T. Umeda

    PHYSICAL REVIEW D   92 ( 9 )   094507   2015.11

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    The reweighting method is widely used in numerical studies of QCD, in particular, for the cases in which the conventional Monte Carlo method cannot be applied directly, e.g., finite density QCD. However, the application range of the reweighing method is restricted due to several problems. One of the most severe problems here is the overlap problem. To solve it, we examine a multipoint reweighting method in which simulations at several simulation points are combined in the data analyses. We systematically study the applicability and limitation of the multipoint reweighting method in two-flavor QCD at zero density. Measuring histograms of physical quantities at a series of simulation points, we apply the multipoint reweighting method to calculate the meson masses as continuous functions of the gauge coupling beta and the hopping parameters kappa. We then determine lines of constant physics and beta functions, which are needed in a calculation of the equation of state at finite temperature.

    DOI: 10.1103/PhysRevD.92.094507

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  • Multipoint reweighting method and beta functions for the calculation of QCD equation of state Reviewed

    R. Iwami, S. Ejiri, K. Kanaya, Y. Nakagawa, T. Umeda, D. Yamamoto, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2014   222   2015.5

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    DOI: 10.22323/1.214.0222

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  • Complex singularities around the QCD critical point at finite densities Reviewed

    Shinji Ejiri, Yasuhiko Shinno, Hiroshi Yoneyama

    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS   2014 ( 8 )   083B02   2014.8

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    Partition function zeros provide an alternative approach for studying the phase structure of finite density QCD. The structure of the Lee-Yang edge singularities associated with the zeros in the complex chemical potential plane has a strong influence on the real axis of the chemical potential. In order to investigate what the singularities are like in a concrete form, we resort to an effective theory based on a mean field approach in the vicinity of the critical point. The crossover is identified as a real part of the singular point. We consider the complex effective potential and explicitly study the behavior of its extrema in the complex order parameter plane in order to see how the Stokes lines are associated with the singularity. Susceptibilities in the complex plane are also discussed.

    DOI: 10.1093/ptep/ptu108

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  • Nature of finite temperature and density phase transitions in many-flavor QCD Reviewed

    Shinji Ejiri, Norikazu Yamada

    Proceedings of Science   LATTICE 2013   146   2014.4

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    DOI: 10.22323/1.187.0146

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  • Scaling properties of the chiral phase transition in the low density region of two-flavor QCD with improved Wilson fermions Reviewed

    T. Umeda, S. Ejiri, K. Kanaya, Y. Maezawa, Y. Nakagawa, H. Ohno, H. Saito, S. Yoshida, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2013   450   2014.4

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    DOI: 10.22323/1.187.0450

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  • Singularities around the QCD critical point in the complex chemical potential plane Reviewed

    Shinji Ejiri, Yasuhiko Shinno, Hiroshi Yoneyama

    Proceedings of Science   LATTICE 2013   210   2014.4

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    DOI: 10.22323/1.187.0210

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  • Histograms in heavy-quark QCD at finite temperature and density Reviewed

    H. Saito, S. Ejiri, S. Aoki, K. Kanaya, Y. Nakagawa, H. Ohno, K. Okuno, T. Umeda

    PHYSICAL REVIEW D   89 ( 3 )   034507   2014.2

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    We study the phase structure of lattice QCD with heavy quarks at finite temperature and density by a histogram method. We determine the location of the critical point at which the first-order deconfining transition in the heavy-quark limit turns into a crossover at intermediate quark masses through a change of the shape of the histogram under variation of coupling parameters. We estimate the effect of the complex phase factor, which causes the sign problem at finite density, and show that, in heavy-quark QCD, the effect is small around the critical point. We determine the critical surface in 2 + 1 flavor QCD in the heavy-quark region at all values of the chemical potential mu including mu = infinity.

    DOI: 10.1103/PhysRevD.89.034507

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  • Phase structure of many flavor lattice QCD at finite temperature Reviewed

    Norikazu Yamada, Shinji Ejiri

    Proceedings of KMI-GCOE Workshop, Strong Coupling Gauge Theories in the LHC Perspective (SCGT 12)   51 - 57   2013.9

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    DOI: 10.1142/9789814566254_0005

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  • Phase structure of hot dense QCD by a histogram method Invited Reviewed

    Shinji Ejiri

    EUROPEAN PHYSICAL JOURNAL A   49 ( 7 )   86   2013.7

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    We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. The quark mass dependence and the chemical potential dependence of the nature of phase transition are investigated focusing on the probability distribution function (histogram). The shape of the distribution function changes with the quark mass and chemical potential. Through the shape of the distribution, the critical surface which separates the first-order transition and crossover regions in the heavy quark region is determined for the (2+1)-flavor case. Moreover, we determined the critical point at finite density for two-flavor QCD with an intermediate quark mass, using a Gaussian approximation of the complex phase distribution of the quark determinant. The chemical potential dependence of the critical quark mass is also evaluated in the situation where two light quarks and many massive quarks exist. We find that the first-order transition region becomes wider with the chemical potential in the many-flavor QCD.

    DOI: 10.1140/epja/i2013-13086-7

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  • End point of a first-order phase transition in many-flavor lattice QCD at finite temperature and density Reviewed

    Shinji Ejiri, Norikazu Yamada

    Physical Review Letters   110 ( 17 )   172001   2013.4

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    Towards the feasibility study of the electroweak baryogenesis in realistic technicolor scenario, we investigate the phase structure of (2+N f)-flavor QCD, where the mass of two flavors is fixed to a small value and the others are heavy. For the baryogenesis, an appearance of a first-order phase transition at finite temperature is a necessary condition. Using a set of configurations of two-flavor lattice QCD and applying the reweighting method, the effective potential defined by the probability distribution function of the plaquette is calculated in the presence of additional many heavy flavors. Through the shape of the effective potential, we determine the critical mass of heavy flavors separating the first-order and crossover regions and find it to become larger with Nf. We moreover study the critical line at finite density and the first-order region is found to become wider as increasing the chemical potential. Possible applications to real (2+1)-flavor QCD are discussed. © 2013 American Physical Society.

    DOI: 10.1103/PhysRevLett.110.172001

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  • Thermodynamics in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach Reviewed

    T. Umeda, S. Aoki, S. Ejiri, T. Hatsuda, K. Kanaya, Y. Maezawa, H. Ohno, HOT-QCD Collaboration

    Proceedings of Science   Lattice 2012   074   2012.12

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    DOI: 10.22323/1.164.0074

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  • Phase structure of finite density QCD with a histogram method Reviewed

    Y. Nakagawa, S. Ejiri, S. Aoki, K. Kanaya, H. Saito, H. Ohno, T. Hatsuda, T. Umeda, HOT-QCD collaboration

    Proceedings of Science   Lattice 2012   092   2012.12

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    DOI: 10.22323/1.164.0092

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  • Probability distribution functions in the finite density lattice QCD Reviewed

    S. Ejiri, Y. Nakagawa, S. Aoki, K. Kanaya, H. Saito, T. Hatsuda, H. Ohno, T. Umeda, HOT-QCD collaboration

    Proceedings of Science   Lattice 2012   089   2012.12

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    DOI: 10.22323/1.164.0089

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  • Numerical study of QCD phase diagram at high temperature and density by a histogram method Reviewed

    Shinji Ejiri, Sinya Aoki, Tetsuo Hatsuda, Kazuyuki Kanaya, Yoshiyuki Nakagawa, Hiroshi Ohno, Hana Saito, Takashi Umeda

    CENTRAL EUROPEAN JOURNAL OF PHYSICS   10 ( 6 )   1322 - 1325   2012.12

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    We study the QCD phase structure at high temperature and density adopting a histogram method. Because the quark determinant is complex at finite density, the Monte-Carlo method cannot be applied directly. We use a reweighting method and try to solve the problems which arise in the reweighting method, i.e. the sign problem and the overlap problem. We discuss the chemical potential dependence of the probability distribution function in the heavy quark mass region and examine the applicability of the approach in the light quark region.

    DOI: 10.2478/s11534-012-0054-7

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  • Application of Fixed Scale Approach to Static Quark Free Energies in Quenched and 2+1 Flavor Lattice QCD with Improved Wilson Quark Action Reviewed

    Yu Maezawa, Takashi Umeda, Sinya Aoki, Shinji Ejiri, Tetsuo Hatsuda, Kazuyuki Kanaya, Hiroshi Ohno

    PROGRESS OF THEORETICAL PHYSICS   128 ( 5 )   955 - 970   2012.11

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    The free energies of static quarks and the Debye screening masses in the quark gluon plasma are studied using Polyakov-line correlation functions in lattice QCD adopting the fixed-scale approach in which temperature is varied without changing the spatial volume and the renormalization factors. We calculate static-quark free energies in various color channels in the high temperature phase up to about 3.5 times the (pseudo-)critical temperature, performing lattice simulations both in quenched and 2+1 flavor QCD. For the quenched simulations, we adopt the plaquette gauge action on anisotropic 20(3) x N-t lattices with N-t = 8-26 at the renormalized anisotropy a(s)/a(t) similar or equal to 4. For 2 + 1 flavor QCD, we adopt the renormalization-group improved Iwasaki gluon action and the non-perturbatively O(alpha)-improved Wilson quark action on isotropic 32(3) x N-t lattices with N-t = 4-12 at m(PS)/m(V) = 0.63 (0.74) for the light (strange) flavors. We find that the color-singlet free energies at high temperatures converge to the zero-temperature static-quark potential evaluated from the Wilson-loop at short distances. This is in accordance with the theoretical expectation that the short distance physics is insensitive to the temperature. At long distances, the free energies approach twice the single-quark free energies, implying that the interaction between static quarks is fully screened. We find that the static-quark free energies for various color channels turn out to be well described by the screened Coulomb form, and the color-channel dependence of the inter-quark interaction can be described by the kinetic Casimir factor inspired from the lowest order perturbation theory. We also discuss comparison with a prediction of the thermal perturbation theory and flavor dependence of the screening masses.

    DOI: 10.1143/PTP.128.955

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  • Finite density QCD phase transition in the heavy quark region Reviewed

    H. Saito, S. Aoki, K. Kanaya, H. Ohno, S. Ejiri, Y. Nakagawa, T. Hatsuda, T. Umeda, HOT-QCD collaboration

    Proceedings of Science   LATTICE 2011   214   2012.7

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    DOI: 10.22323/1.139.0214

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  • Histogram method in finite density QCD with phase quenched simulations Reviewed

    Y. Nakagawa, S. Ejiri, S. Aoki, K. Kanaya, H. Ohno, H. Saito, T. Hatsuda, T. Umeda, HOT-QCD collaboration

    Proceedings of Science   LATTICE 2011   208   2012.7

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    DOI: 10.22323/1.139.0208

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  • Equation of state in 2+1 flavor QCD with improved Wilson quarks by the fixed scale approach Reviewed

    T. Umeda, S. Aoki, S. Ejiri, T. Hatsuda, K. Kanaya, H. Ohno, Y. Maezawa

    PHYSICAL REVIEW D   85 ( 9 )   094508   2012.5

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    We study the equation of state in 2 + 1 flavor QCD with nonperturbatively improved Wilson quarks coupled with the renormalization group-improved Iwasaki glue. We apply the T-integration method to nonperturbatively calculate the equation of state by the fixed-scale approach. With the fixed-scale approach, we can purely vary the temperature on a line of constant physics without changing the system size and renormalization constants. Unlike the conventional fixed-N-t approach, it is easy to keep scaling violations small at low temperature in the fixed-scale approach. We study 2 + 1 flavor QCD at light quark mass corresponding to m(pi)/m(rho) similar or equal to 0.63, while the strange quark mass is chosen around the physical point. Although the light quark masses are still heavier than the physical values, our equation of state is roughly consistent with recent results with highly improved staggered quarks at large N-t.

    DOI: 10.1103/PhysRevD.85.094508

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  • Erratum: Phase structure of finite temperature QCD in the heavy quark region [Phys. Rev. D84, 054502 (2011)] Reviewed

    H. Saito, S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, H. Ohno, T. Umeda

    Physical Review D   85 ( 7 )   079902 - 79902   2012.4

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    DOI: 10.1103/physrevd.85.079902

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  • Ab initio study of the thermodynamics of quantum chromodynamics on the lattice at zero and finite densities Invited Reviewed

    Shinji Ejiri, Kazuyuki Kanaya, Takashi Umeda

    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS   2012 ( 1 )   01A104   2012

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    The WHOT-QCD Collaboration is pushing forward a series of lattice studies of quantum chromodynamics (QCD) at finite temperatures and densities using improved Wilson quarks. Because Wilson-type quarks require more computational resources than the more widely used staggered-type quarks, various theoretical and computational techniques have to be developed and applied. In this paper, we introduce a fixed-scale approach armed with a T-integration method, a Gaussian method based on cumulant expansion, and a histogram method combined with the reweighting technique. Using these methods, we have carried out the first study of finite-density QCD with Wilson-type quarks and the first calculation of the equation of state with 2 + 1 flavors of Wilson-type quarks. We present the results of these studies and discuss perspectives towards clarification of the properties of 2 + 1 flavor QCD at the physical point at finite temperatures and densities.

    DOI: 10.1093/ptep/pts005

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  • Charmonium spectral functions with the variational method in zero and finite temperature lattice QCD Reviewed

    H. Ohno, S. Aoki, S. Ejiri, K. Kanaya, Y. Maezawa, H. Saito, T. Umeda

    PHYSICAL REVIEW D   84 ( 9 )   94504   2011.11

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    We propose a method to evaluate spectral functions on the lattice based on a variational method. On a lattice with a finite spatial extent, spectral functions consist of discrete spectra only. Adopting a variational method, we calculate the locations and the heights of spectral functions at low-lying discrete spectra. We first test the method in the case of analytically solvable free Wilson quarks at zero and finite temperatures and confirm that the method well reproduces the analytic results for low-lying spectra. We find that we can systematically improve the results by increasing the number of trial states. We then apply the method to calculate the charmonium spectral functions for S and P-wave states at zero-temperature in quenched QCD and compare the results with those obtained using the conventional maximum entropy method (MEM). The results for the ground state are consistent with the location and the area of the first peak in spectral functions from the MEM, while the variational method leads to a mass which is closer to the experimental value for the first excited state. We also investigate the temperature dependence of the spectral functions for S-wave states below and above T-c. We obtain no clear evidences for dissociation of J/Psi and eta(c) up to 1.4T(c).

    DOI: 10.1103/PhysRevD.84.094504

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  • Phase structure of finite temperature QCD in the heavy quark region Reviewed

    H. Saito, S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, H. Ohno, T. Umeda

    PHYSICAL REVIEW D   84 ( 5 )   54502   2011.9

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    We study the quark mass dependence of the finite temperature QCD phase transition in the heavy quark region using an effective potential defined through the probability distribution function of the average plaquette. Performing a simulation of SU(3) pure gauge theory, we first confirm that the distribution function has two peaks indicating that the phase transition is of first order in the heavy quark limit, while the first-order transition turns into a crossover as the quark mass decreases from infinity, where the mass dependence of the distribution function is evaluated by the reweighting method combined with the hopping parameter expansion. We determine the endpoint of the first-order transition region for N(f) = 1, 2, 3 and 2 + 1 cases. The quark mass dependence of the latent heat is also evaluated in the first-order transition region.

    DOI: 10.1103/PhysRevD.84.054502

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  • An application of the variational analysis to calculate the meson spectral functions Reviewed

    H. Ohno, S. Aoki, S. Ejiri, K. Kanaya, Y. Maezawa, H. Saito, T. Umeda, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2010   209   2011.6

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    DOI: 10.22323/1.105.0209

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  • The order of the deconfinement phase transition in a heavy quark mass region Reviewed

    H. Saito, S. Aoki, K. Kanaya, H. Ohno, S. Ejiri, T. Hatsuda, Y. Maezawa, T. Umeda, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2010   212   2011.6

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    DOI: 10.22323/1.105.0212

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  • EOS in 2+1 flavor QCD with improved Wilson quarks by the fixed-scale approach Reviewed

    T. Umeda, S. Aoki, K. Kanaya, H. Ohno, S. Ejiri, T. Hatsuda, Y. Maezawa, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2010   218   2011.6

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    DOI: 10.22323/1.105.0218

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  • Scaling behavior of chiral phase transition in two-flavor QCD with improved Wilson quarks at finite density Reviewed

    S. Ejiri, Y. Nakagawa, S. Aoki, K. Kanaya, H. Ohno, H. Saito, T. Hatsuda, Y. Maezawa, T. Umeda, HOT-QCD collaboration

    Proceedings of Science   LATTICE 2010   181   2011.6

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    DOI: 10.22323/1.105.0181

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  • Equation of state and heavy-quark free energy at finite temperature and density in two flavor lattice QCD with Wilson quark action Reviewed

    S. Ejiri, Y. Maezawa, N. Ukita, S. Aoki, T. Hatsuda, N. Ishii, K. Kanaya, T. Umeda

    PHYSICAL REVIEW D   82 ( 1 )   14508   2010.7

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    We study the equation of state at finite temperature and density in two-flavor QCD with the renormalization group improved gluon action and the clover-improved Wilson quark action on a 16(3) X 4 lattice. Along the lines of constant physics at m(PS)/m(V) = 0.65 and 0.80, we compute the second and forth derivatives of the grand canonical partition function with respect to the quark chemical potential mu(q) = (mu(u) + mu(d))/2 and the isospin chemical potential mu(I) = (mu(u) - mu(d))/2 at vanishing chemical potentials, and study the behaviors of thermodynamic quantities at finite mu(q) using these derivatives for the case mu(I) = 0. In particular, we study density fluctuations at nonezero temperature and density by calculating the quark number and isospin susceptibilities and their derivatives with respect to mu(q). To suppress statistical fluctuations, we also examine new techniques applicable at low densities. We find a large enhancement in the fluctuation of the quark number when the density increased near the pseudocritical temperature, suggesting a critical point at finite mu(q) terminating the first order transition line between hadronic and quark-gluon-plasma phases. This result agrees with the previous results using staggered-type quark actions qualitatively. Furthermore, we study heavy-quark free energies and Debye screening masses at finite density by measuring the first and second derivatives of these quantities for various color channels of heavy quark-quark and quark-antiquark pairs. The results suggest that, to the leading order of mu(q), the interaction between two quarks becomes stronger at finite densities, while that between quark and antiquark becomes weaker.

    DOI: 10.1103/PhysRevD.82.014508

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  • Towards the equation of state in 2+1 flavor QCD with improved Wilson quarks in the fixed scale approach Reviewed

    K. Kanaya, S. Aoki, H. Ohno, T. Umeda, S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, HOT-QCD Collaboration

    Proceedings of Science   LAT2009   190   2010.6

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    DOI: 10.22323/1.091.0190

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  • Singularities of QCD in the complex chemical potential plane Reviewed

    Shinji Ejiri, Hiroshi Yoneyama

    Proceedings of Science   LAT2009   173   2010.6

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    DOI: 10.22323/1.091.0173

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  • Third moments of conserved charges in QCD phase diagram Reviewed

    Masakiyo Kitazawa, Masayuki Asakawa, Shinji Ejiri

    Proceedings of Science   LAT2009   174   2010.6

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    DOI: 10.22323/1.091.0174

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  • Heavy-quark free energy at finite temperature with 2+1 flavors of improved Wilson quarks in fixed scale approach Reviewed

    Y. Maezawa, S. Aoki, S. Ejiri, T. Hatsuda, K. Kanaya, H. Ohno, T. Umeda, HOT-QCD Collaboration

    Proceedings of Science   LAT2009   165   2010.6

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    DOI: 10.22323/1.091.0165

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  • Electric and magnetic screening masses at finite temperature from generalized Polyakov-line correlations in two-flavor lattice QCD Reviewed

    Y. Maezawa, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, K. Kanaya, N. Ukita, T. Umeda

    PHYSICAL REVIEW D   81 ( 9 )   91501   2010.5

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    Screenings of the quark-gluon plasma in electric and magnetic sectors are studied on the basis of generalized Polyakov-line correlation functions in lattice QCD simulations with two flavors of improved Wilson quarks. Using the Euclidean-time reflection (R) and the charge conjugation (C), electric and magnetic screening masses are extracted in a gauge-invariant manner. Long distance behavior of the standard Polyakov-line correlation in the quark-gluon plasma is found to be dictated by the magnetic screening. Also, the ratio of the two screening masses agrees with that obtained from the dimensionally-reduced effective field theory and the N = 4 supersymmetric Yang-Mills theory.

    DOI: 10.1103/PhysRevD.81.091501

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  • Equation of state for physical quark masses Reviewed

    M. Cheng, S. Ejiri, P. Hegde, F. Karsch, O. Kaczmarek, E. Laermann, R. D. Mawhinney, C. Miao, S. Mukherjee, P. Petreczky, C. Schmidt, W. Soeldner

    PHYSICAL REVIEW D   81 ( 5 )   54504   2010.3

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    We calculate the QCD equation of state for temperatures corresponding to the transition region with physical mass values for two degenerate light quark flavors and a strange quark using an improved staggered fermion action (p4-action) on lattices with temporal extent N-tau = 8. We compare our results with previous calculations performed at twice larger values of the light quark masses as well as with results obtained from a resonance gas model calculation. We also discuss the deconfining and chiral aspects of the QCD transition in terms of renormalized Polyakov loop, strangeness fluctuations, and subtracted chiral condensate. We show that compared to the calculations performed at twice larger value of the light quark mass the transition region shifts by about 5 MeV toward smaller temperatures.

    DOI: 10.1103/PhysRevD.81.054504

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  • Lattice QCD at Finite Temperature and Density Reviewed

    Shinji Ejiri

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   186 ( 186 )   510 - 515   2010

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    We study the phase structure of QCD at finite temperature and density by numerical simulations on a lattice. The most important point for the numerical study at finite density is treatment of the sign problem. We propose a method to avoid the sign problem, which is based on a cumulant expansion of the complex phase in the density of state method combined with the reweighting method. Using the method, we study the critical point terminating a first order phase transition line in lattice QCD at high temperature and density.

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  • QCD Thermodynamics at Zero and Finite Densities with Improved Wilson Quarks Reviewed

    K. Kanaya, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, H. Ohno, H. Saito, N. Ukita, T. Umeda

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   186 ( 186 )   556 - 562   2010

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    The WHOT-QCD Collaboration is pushing forward lattice studies of QCD at finite temperatures and densities using improved Wilson quarks. We first present results on QCD at zero and finite densities with two flavors of degenerate quarks (N(F) = 2 QCD) adopting the conventional fixed-N(t) approach. We then report on the status of a study of N(F) = 2 + 1 QCD adopting a fixed-scale approach armed with the T-integration method which we have developed.

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  • Third Moments of Conserved Charges as Probes of QCD Phase Structure Reviewed

    Masayuki Asakawa, Shinji Ejiri, Masakiyo Kitazawa

    PHYSICAL REVIEW LETTERS   103 ( 26 )   262301   2009.12

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    The third moments of conserved charges, the baryon and electric charge numbers, and energy, as well as their mixed moments, carry more information on the state around the QCD phase boundary than previously proposed fluctuation observables and higher order moments. In particular, their signs give plenty of information on the location of the state created in relativistic heavy ion collisions in the temperature and baryon chemical potential plane. We demonstrate this with an effective model.

    DOI: 10.1103/PhysRevLett.103.262301

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  • The RBC-Bielefeld Collaboration Reviewed

    Michael Cheng, Norman Christ, Saumen Datta, Shinji Ejiri, Chulwoo Jung, Olaf Kaczmarek, Frithjof Karsch, Edwin Laermann, Robert Mawhinney, Chuan Miao, Swagato Mukherjee, Peter Petreczky, Konstantin Petrov, Christian Schmidt, Wolfgang Soeldner, Takashi Umeda, Wolfgang Unger, Alexander Velytsky

    Nuclear Physics A   830 ( 1-4 )   968   2009.11

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    DOI: 10.1016/j.nuclphysa.2009.10.155

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  • Free energies of heavy quarks in full-QCD lattice simulations with Wilson-type quark action Reviewed

    Y. Maezawa, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, K. Kanaya, H. Ohno, T. Umeda

    NUCLEAR PHYSICS A   830   247C - 250C   2009.11

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    The free energy between a static quark and an antiquark is studied by using the color-singlet Polyakov-line correlation at finite temperature in lattice QCD with 2+1 flavors of improved Wilson quarks. From the simulations on 32(3) X 12, 10, 8, 6, 4 lattices in the high temperature phase, based on the fixed scale approach, we find that, the heavy-quark free energies at short distance converge to the heavy-quark potential evaluated from the Wilson loop at zero temperature, in accordance with the expected insensitivity of short distance physics to the temperature. At long distance, the heavy-quark free energies approach to twice the single-quark free energies, implying that the interaction between heavy quarks is screened. The Debye screening mass obtained from the long range behavior of the free energy is compared with the results of thermal perturbation theory.

    DOI: 10.1016/j.nuclphysa.2009.10.021

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  • Magnetic equation of state in (2+1)-flavor QCD Reviewed

    S. Ejiri, F. Karsch, E. Laermann, C. Miao, S. Mukherjee, P. Petreczky, C. Schmidt, W. Soeldner, W. Unger

    PHYSICAL REVIEW D   80 ( 9 )   94505   2009.11

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    A first study of critical behavior in the vicinity of the chiral phase transition of (2+1)-flavor QCD is presented. We analyze the quark mass and volume dependence of the chiral condensate and chiral susceptibilities in QCD with two degenerate light quark masses and a strange quark. The strange quark mass (m(s)) is chosen close to its physical value; the two degenerate light quark masses (m(l)) are varied in a wide range 1/80 &lt; m(l)/m(s)&lt; 2/5, where the smallest light quark mass value corresponds to a pseudoscalar Goldstone mass of about 75 MeV. All calculations are performed with staggered fermions on lattices with temporal extent N-tau=4. We show that numerical results are consistent with O(N) scaling in the chiral limit. We find that in the region of physical light quark mass values, m(l)/m(s)similar or equal to 1/20, the temperature and quark mass dependence of the chiral condensate is already dominated by universal properties of QCD that are encoded in the scaling function for the chiral order parameter, the magnetic equation of state. We also provide evidence for the influence of thermal fluctuations of Goldstone modes on the chiral condensate at finite temperature. At temperatures below, but close to the chiral phase transition at vanishing quark mass, this leads to a characteristic dependence of the light quark chiral condensate on the square root of the light quark mass.

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  • Critical point in finite density lattice QCD by canonical approach Reviewed

    Shinji Ejiri

    NUCLEAR PHYSICS A   830   717C - 720C   2009.11

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    We propose a method to find the QCD critical point at finite density calculating the canonical partition function Z(C)(T, N) by Monte-Carlo simulations of lattice QCD, and analyze data obtained by a simulation with two-flavor p4-improved staggered quarks with pion mass m(pi) approximate to 770MeV. It is found that the shape of an effective potential changes gradually as the temperature decreases and a first order phase transition appears in the low temperature and high density region. This result strongly Suggests the existence of the critical point in the (T, mu(q)) phase diagram.

    DOI: 10.1016/j.nuclphysa.2009.09.060

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  • Fixed scale approach to the equation of state on the lattice Reviewed

    K. Kanaya, T. Umeda, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, H. Ohno

    NUCLEAR PHYSICS A   830   801C - 804C   2009.11

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    We propose a fixed scale approach to calculate the equation of state (EOS) in lattice QCD. In this approach, the temperature T is varied by N(t) at fixed lattice spacings. This enables us to reduce T = 0 simulations which are required to provide basic data in finite temperature studies but are quite expensive in the conventional fixed-N(t) approach. Since the conventional integral method to obtain the pressure is inapplicable at fixed scale, we introduce a new method, "T-integration method", to calculate pressure non-perturbatively. We test the fixed scale approach armed with the T-integral method in quenched QCD on isotropic and anisotropic lattices. Our method is found to be powerful to obtain reliable results for the equation of state, especially at intermediate and low temperatures. Reduction of the computational cost of T = 0 simulations is indispensable to study EOS in QCD with dynamical quarks. The status of our study in N(f) = 2 + 1 QCD with improved Wilson quarks is also reported.

    DOI: 10.1016/j.nuclphysa.2009.10.004

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  • Equation of state and QCD transition at finite temperature Reviewed

    A. Bazavov, T. Bhattacharya, M. Cheng, N. H. Christ, C. DeTar, S. Ejiri, Steven Gottlieb, R. Gupta, U. M. Heller, K. Huebner, C. Jung, F. Karsch, E. Laermann, L. Levkova, C. Miao, R. D. Mawhinney, P. Petreczky, C. Schmidt, R. A. Soltz, W. Soeldner, R. Sugar, D. Toussaint, P. Vranas

    PHYSICAL REVIEW D   80 ( 1 )   14504   2009.7

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    We calculate the equation of state in 2+1 flavor QCD at finite temperature with physical strange quark mass and almost physical light quark masses using lattices with temporal extent N(tau)=8. Calculations have been performed with two different improved staggered fermion actions, the asqtad and p4 actions. Overall, we find good agreement between results obtained with these two O(a(2)) improved staggered fermion discretization schemes. A comparison with earlier calculations on coarser lattices is performed to quantify systematic errors in current studies of the equation of state. We also present results for observables that are sensitive to deconfining and chiral aspects of the QCD transition on N(tau)=6 and 8 lattices. We find that deconfinement and chiral symmetry restoration happen in the same narrow temperature interval. In an appendix we present a simple parametrization of the equation of state that can easily be used in hydrodynamic model calculations. In this parametrization we include an estimate of current uncertainties in the lattice calculations which arise from cutoff and quark mass effects.

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  • Recent progress in lattice QCD at finite density Reviewed

    Shinji Ejiri

    Proceedings of Science   LATTICE 2008   2   2009.6

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    DOI: 10.22323/1.066.0002

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  • Magnetic and electric screening masses from Polyakov-line correlations Reviewed

    Y. Maezawa, S. Aoki, K. Kanaya, S. Ejiri, T. Hatsuda, N. Ishii, N. Ukita, T. Umeda, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2008   194   2009.6

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    DOI: 10.22323/1.066.0194

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  • Equation of state at finite density in two-flavor QCD with improved Wilson quarks Reviewed

    K. Kanaya, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, N. Ukita, T. Umeda, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2008   189   2009.6

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    DOI: 10.22323/1.066.0189

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  • Thermodynamics of SU(3) gauge theory at fixed lattice spacing Reviewed

    T. Umeda, S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, H. Ohno, HOT-QCD Collaboration

    Proceedings of Science   LATTICE 2008   174   2009.6

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    DOI: 10.22323/1.066.0174

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  • Fixed scale approach to equation of state in lattice QCD Reviewed

    T. Umeda, S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, H. Ohno

    PHYSICAL REVIEW D   79 ( 5 )   51501   2009.3

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    A new approach to study the equation of state in finite-temperature QCD is proposed on the lattice. Unlike the conventional method in which the temporal lattice size N(t) is fixed, the temperature T is varied by changing N(t) at the fixed lattice scale. The pressure of the hot QCD plasma is calculated by the integration of the trace anomaly with respect to T at the fixed lattice scale. This "T-integral method&apos;&apos; is tested in quenched QCD on isotropic and anisotropic lattices and is shown to give reliable results, especially at intermediate and low temperatures.

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  • Canonical partition function and finite density phase transition in lattice QCD Reviewed

    Shinji Ejiri

    PHYSICAL REVIEW D   78 ( 7 )   74507   2008.10

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    We discuss the nature of the phase transition for lattice QCD at finite temperature and density. We propose a method to calculate the canonical partition function by fixing the total quark number introducing approximations allowed in the low density region. An effective potential as a function of the quark number density is discussed from the canonical partition function. We analyze data obtained in a simulation of two-flavor QCD using p4-improved staggered quarks with bare quark mass m/T=0.4 on a 16(3)x4 lattice. The results suggest that the finite density phase transition at low temperature is of first order.

    DOI: 10.1103/PhysRevD.78.074507

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  • Study of the critical point in lattice QCD at high temperature and density Reviewed

    Shinji Ejiri

    Proceedings of Science   LATTICE 2007   181   2008.3

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    DOI: 10.22323/1.042.0181

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  • Thermodynamics and heavy-quark free energies at finite temperature and density with two flavors of improved Wilson quarks Reviewed

    Y. Maezawa, T. Hatsuda, S. Aoki, K. Kanaya, S. Ejiri, N. Ishii, N. Ukita, T. Umeda

    Proceedings of Science   LATTICE 2007   207   2008.3

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    DOI: 10.22323/1.042.0207

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  • Existence of the critical point in finite density lattice QCD Reviewed

    Shinji Ejiri

    PHYSICAL REVIEW D   77 ( 1 )   14508   2008.1

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    We propose a method to probe the nature of phase transitions in lattice QCD at finite temperature and density, which is based on the investigation of an effective potential as a function of the average plaquette. We analyze data obtained in a simulation of two-flavor QCD using p4-improved staggered quarks with bare quark mass m/T=0.4 and find that a first order phase transition line appears in the high density regime for mu(q)/T greater than or similar to 2.5. We also discuss the difference between the phase structures of QCD with nonzero quark chemical potential and nonzero isospin chemical potential.

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  • Thermodynamics of two-flavour lattice QCD with an improved Wilson quark action at non-zero temperature and density Reviewed

    Y. Maezawa, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, K. Kanaya, N. Ukita

    Journal of Physics G: Nuclear and Particle Physics   34 ( 8 )   S651 - S654   2007.8

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    We report the current status of our systematic studies of the QCD thermodynamics by lattice QCD simulations with two flavours of improved Wilson quarks. We evaluate the critical temperature of two-flavour QCD in the chiral limit at a zero chemical potential and show the preliminary result. Also we discuss fluctuations at non-zero temperature and density by calculating the quark number and isospin susceptibilities and their derivatives with respect to the chemical potential. © 2007 IOP Publishing Ltd.

    DOI: 10.1088/0954-3899/34/8/S65

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  • Heavy-quark free energy, Debye mass, and spatial string tension at finite temperature in two flavor lattice QCD with Wilson quark action Reviewed

    Y. Maezawa, N. Ukita, S. Aoki, S. Ejiri, T. Hatsuda, N. Ishii, K. Kanaya

    PHYSICAL REVIEW D   75 ( 7 )   74501   2007.4

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    We study Polyakov loop correlations and spatial Wilson loop at finite temperature in two-flavor QCD simulations with the RG-improved gluon action and the clover-improved Wilson quark action on a 16(3)x4 lattice. From the line of constant physics at m(PS)/m(V)=0.65 and 0.80, we extract the heavy-quark free energies, the effective running coupling g(eff)(T) and the Debye screening mass m(D)(T) for various color channels of heavy quark-quark and quark-antiquark pairs above the critical temperature. The free energies are well approximated by the screened Coulomb form with the appropriate Casimir factors at high temperature. The magnitude and the temperature dependence of the Debye mass are compared to those of the next-to-leading-order thermal perturbation theory and to a phenomenological formula in terms of g(eff)(T). We make a comparison between our results with the Wilson quark action and the previous results with the staggered quark action. The spatial string tension is also studied in the high temperature phase and is compared to the next-to-next-leading-order prediction in an effective theory with dimensional reduction.

    DOI: 10.1103/PhysRevD.75.074501

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  • Lattice QCD thermodynamics with Wilson quarks Reviewed

    Shinji Ejiri

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   168 ( 168 )   245 - 252   2007

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    We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.

    DOI: 10.1143/PTPS.168.245

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  • Equation of state for two-flavor QCD with an improved Wilson quark action at non-zero chemical potential Reviewed

    S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, N. Ukita, S. Aoki, K. Kanaya

    Proceedings of Science   LAT2006   132   2006.12

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    DOI: 10.22323/1.032.0132

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  • Finite temperature phase transition of two-flavor QCD with an improved Wilson quark action Reviewed

    N. Ukita, S. Ejiri, T. Hatsuda, N. Ishii, Y. Maezawa, S. Aoki, K. Kanaya

    Proceedings of Science   LAT2006   150   2006.12

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    DOI: 10.22323/1.032.0150

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  • Static quark free energies at finite temperature with two flavors of improved Wilson quarks Reviewed

    Y. Maezawa, S. Ejiri, T. Hatsuda, N. Ishii, N. Ukita, S. Aoki, K. Kanaya

    Proceedings of Science   LAT2006   141   2006.12

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    DOI: 10.22323/1.032.0141

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  • Hadronic fluctuations in the QGP Reviewed

    F. Karsch, S. Ejiri, K. Redlich

    NUCLEAR PHYSICS A   774   619 - 622   2006.8

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    We analyze fluctuations of quark number and electric charge, in 2-flavour QCD at finite temperature and vanishing net baryon number density. In the hadronic phase we find that an enhancement of charge fluctuations arises from contributions of doubly charged hadrons to the thermodynamics. The rapid suppression of fluctuations seen in the high temperature phase suggests that in the QGP quark number and electric charge are predominantly carried by quasi-particles with the quantum numbers of quarks.

    DOI: 10.1016/j.nuclphysa.2006.06.099

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  • The QCD equation of state for two flavours at non-zero chemical potential Reviewed

    S. Ejiri, C. R. Allton, M. Doering, S. J. Hands, O. Kaczmarek, F. Karsch, E. Laermann, K. Redlich

    NUCLEAR PHYSICS A   774   837 - 840   2006.8

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    We present results of a simulation of 2 flavour QCD on a 16(3) x 4 lattice using p4-improved staggered fermions with bare quark mass m/T = 0.4. Derivatives of the thermodynamic grand canonical partition function Z(V,T,mu(mu,) mu(d)) with respect to chemical potentials mu(mu,d) for different quark flavours are calculated up to sixth order, enabling estimates of the pressure and the quark number density as well as the chiral condensate and various susceptibilities as functions Of mu(mu,d) via Taylor series expansion. Results are compared to high temperature perturbation theory as well as a hadron resonance gas model. We also analyze baryon as well as isospin fluctuations and discuss the relation to the chiral critical point in the QCD phase diagram. We moreover discuss the dependence of the heavy quark free energy on the chemical potential.

    DOI: 10.1016/j.nuclphysa.2006.06.023

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  • Screening of heavy quark free energies at finite temperature and non-zero baryon chemical potential Reviewed

    M. Doering, S. Ejiri, O. Kaczmarek, F. Karsch, E. Laermann

    EUROPEAN PHYSICAL JOURNAL C   46 ( 1 )   179 - 189   2006.4

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    We analyze the dependence of heavy quark free energies on the baryon chemical potential mu(b) in 2-flavor QCD by performing a 6th order Taylor expansion in the chemical potential which circumvents the sign problem. The bare quark mass at (m) over cap /T = 0.4 corresponds to a pion mass of about 770 MeV and is thus not in the range of physical quark masses but the quark mass dependence is known. to be small above T-c. At N-tau = 4 the lattices are coarse, however, we are using improved (p4 staggered) fermions. The Taylor expansion coefficients of color singlet and color averaged free energies are calculated and from this the expansion coefficients for the corresponding screening masses are determined. We find that for small mu(b) the free energies of a static quark-antiquark pair decrease in a medium with a net excess of quarks and that screening is well described by a screening mass which increases with increasing mu(b). The mu(b)-dependent corrections to the screening masses are well described by perturbation theory for T greater than or similar to 2T(c). In particular, we find for all temperatures above T. that the expansion coefficients for singlet and color averaged screening masses differ by a factor 2.

    DOI: 10.1140/epjc/s2005-02462-y

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  • Lee-Yang zero analysis for the study of QCD phase structure Reviewed

    S Ejiri

    PHYSICAL REVIEW D   73 ( 5 )   54502   2006.3

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    We comment on the Lee-Yang zero analysis for the study of the phase structure of QCD at high temperature and baryon number density by Monte-Carlo simulations. We find that the sign problem for nonzero density QCD induces a serious problem in the finite volume scaling analysis of the Lee-Yang zeros for the investigation of the order of the phase transition. If the sign problem occurs at large volume, the Lee-Yang zeros will always approach the real axis of the complex parameter plane in the thermodynamic limit. This implies that a scaling behavior which would suggest a crossover transition will not be obtained. To clarify this problem, we discuss the Lee-Yang zero analysis for SU(3) pure gauge theory as a simple example without the sign problem, and then consider the case of nonzero density QCD. It is suggested that the distribution of the Lee-Yang zeros in the complex parameter space obtained by each simulation could be more important information for the investigation of the critical endpoint in the (T,mu(q)) plane than the finite volume scaling behavior.

    DOI: 10.1103/PhysRevD.73.054502

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  • Isentropic equation of state of 2-flavor QCD Reviewed

    S Ejiri, F Karsch, E Laermann, C Schmidt

    PHYSICAL REVIEW D   73 ( 5 )   54506   2006.3

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    Using Taylor expansions of the pressure obtained previously in studies of 2-flavor QCD at nonzero chemical potential we calculate expansion coefficients for the energy and entropy densities up to O(mu(6)(q)) in the quark chemical potential. We use these series in mu(q)/T to determine lines of constant entropy per baryon number (S/N-B) that characterize the expansion of dense matter created in heavy ion collisions. In the high temperature regime these lines are found to be well approximated by lines of constant mu(q)/T. In the low temperature phase, however, the quark chemical potential is found to increase with decreasing temperature. This is in accordance with resonance gas model calculations. Along the lines of constant S/N-B we calculate the energy density and pressure. Within the accuracy of our present analysis we find that the ratio p/epsilon for T &gt; T-0 as well as the softest point of the equation of state, (p/epsilon)(min)similar or equal to 0.075, show no significant dependence on S/N-B.

    DOI: 10.1103/PhysRevD.73.054506

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  • Hadronic fluctuations at the QCD phase transition Reviewed

    S Ejiri, F Karsch, K Redlich

    PHYSICS LETTERS B   633 ( 2-3 )   275 - 282   2006.2

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    We discuss the properties of hadronic fluctuations, i.e., fluctuations of net quark and isospin numbers as well as electric charge, in the vicinity of the QCD transition in isospin-symmetric matter at vanishing quark chemical potential. We analyse second-and fourth-order cumulants of these fluctuations and argue that the ratio of quartic and quadratic cumulants reflects the relevant degrees of freedom that carry the quark number, isospin or charge, respectively. In the hadronic phase we find that an enhancement of charge fluctuations arises from contributions of doubly charged hadrons to the thermodynamics. The rapid suppression of fluctuations seen in the high-temperature phase suggests that in the QGP, net quark number and electric charge are predominantly carried by quasi-particles, with the quantum numbers of quarks. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physletb.2005.11.083

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  • Heavy quark free energies and screening at finite temperature and non-zero baryon chemical potential Reviewed

    M. Döring, S. Ejiri, O. Kaczmarek, F. Karsch, E. Laermann

    Proceedings of Extreme QCD, Swansea 2005   93 - 97   2006.1

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  • Heavy quark free energies and screening at finite temperature and density Reviewed

    M. Döring, S. Ejiri, O. Kaczmarek, F. Karsch, E. Laermann

    Proceedings of Science   LAT2005   193   2005.12

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    DOI: 10.22323/1.020.0193

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  • QCD Level Density from Maximum Entropy Method Reviewed

    Shinji Ejiri, Tetsuo Hatsuda

    Proceedings of Science   LAT2005   183   2005.12

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    DOI: 10.22323/1.020.0183

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  • QCD at non-zero temperature and density from the Lattice Reviewed

    CR Allton, S Ejiri, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   141   186 - 190   2005.4

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    The study of systems as diverse as the cores of neutron stars and heavy-ion collision experiments requires the understanding of the phase structure of QCD at non-zero temperature, T, and chemical potential, mu(q). We review some of the difficulties of performing lattice simulations of QCD with mu(q) not equal 0, and outline the re-weighting method used to overcome this problem. This method is used to determine the critical endpoint of QCD in the (mu(q), T) plane. We study the pressure and quark number susceptibility at small mu(q).

    DOI: 10.1016/j.nuclphysbps.2004.12.028

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  • Thermodynamics of two flavor QCD to sixth order in quark chemical potential Reviewed

    CR Allton, M Doring, S Ejiri, SJ Hands, O Kaczmarek, F Karsch, E Laermann, K Redlich

    PHYSICAL REVIEW D   71 ( 5 )   54508   2005.3

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    We present results of a simulation of two flavor QCD on a 16(3) X 4 lattice using p4-improved staggered fermions with bare quark mass m/T = 0.4. Derivatives of the thermodynamic grand canonical partition function Z(V, T, mu(mu), mu(d)) with respect to chemical potentials mu(mu,d) for different quark flavors are calculated up to sixth order, enabling estimates of the pressure and the quark number density as well as the chiral condensate and various susceptibilities as functions of mu(q) = (mu(mu) + mu(d))/2 via Taylor series expansion. Furthermore, we analyze baryon as well as isospin fluctuations and discuss the relation between the radius of convergence of the Taylor series and the chiral critical point in the QCD phase diagram. We argue that bulk thermodynamic observables do not, at present, provide direct evidence for the existence of a chiral critical point in the QCD phase diagram. Results are compared to high temperature perturbation theory as well as a hadron resonance gas model.

    DOI: 10.1103/PhysRevD.71.054508

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  • Fluctuations in the vicinity of the phase transition line for two flavor QCD Reviewed

    S Ejiri, CR Allton, M Doring, SJ Hands, O Kaczmarek, F Karsch, E Laermann, K Redlich

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   140   505 - 507   2005.3

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    We study the susceptibilities of quark number, isospin number and electric charge in numerical simulations of lattice QCD at high temperature and density. We discuss the equation of state for 2 flavor QCD at non-zero temperature and density. Derivatives of In Z with respect to quark chemical potential (mu(q)) are calculated up to sixth order. From this Taylor series, the susceptibilities are estimated as functions of temperature and mu(q). Moreover, we comment on the hadron resonance gas model, which explains well our simulation results below T-c.

    DOI: 10.1016/j.nuclphysbps.2004.11.336

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  • Numerical study of the equation of state for two flavor QCD at non-zero baryon density Reviewed

    S Ejiri, CR Allton, M Doring, SJ Hands, O Kaczmarek, F Karsch, E Laermann, K Redlich

    STRONG AND ELECTROWEAK MATTER 2004, PROCEEDINGS   336 - 340   2005.1

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    We discuss the equation of state (EoS) for two flavor QCD at non-zero temperature and density. Derivatives of In Z with respect to quark chemical potential mu(q) are calculated up to sixth order. From this Taylor series, the pressure, quark number density and associated susceptibilities are estimated as functions of temperature and mu(q). It is found that the fluctuations in the quark number density increase in the vicinity of the phase transition temperature and the susceptibilities start to develop a pronounced peak as mu(q) is increased. This suggests the presence of a critical endpoint in the (mu(q), T) plane. Moreover, we comment on the hadron resonance gas model, which explains well our simulation results below T-c.

    DOI: 10.1142/9789812702159_0050

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  • Equation of state for two flavor QCD at nonzero chemical potential Reviewed

    CR Allton, S Ejiri, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    PHYSICAL REVIEW D   68 ( 1 )   14507   2004.5

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    We present results of a simulation of QCD on a 16(3)x4 lattice with 2 continuum flavors of a p4-improved staggered fermion with mass m/T = 0.4. Derivatives of the thermodynamic grand potential Omega with respect to the quark chemical potential mu(q) up to fourth order are calculated, enabling estimates of the pressure, quark number density and associated susceptibilities as functions of mu(q) via Taylor series expansion. Discretization effects associated with various staggered fermion formulations are discussed in some detail. In addition it is possible to estimate the radius of convergence of the expansion as a function of temperature. We also discuss the calculation of energy and entropy densities which are defined via mixed derivatives of Omega with respect to the bare couplings and quark masses.

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  • Remarks on the multiparameter reweighting method for the study of lattice QCD at nonzero temperature and density Reviewed

    S Ejiri

    PHYSICAL REVIEW D   69 ( 9 )   94506   2004.5

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    We comment on the reweighting method for the study of finite density lattice QCD. We discuss the applicable parameter range of the reweighting method for models that have more than one simulation parameter. The applicability range is determined by the fluctuations of the modification factor of the Boltzmann weight. In some models having a first order phase transition, the fluctuations are minimized along the phase transition line if we assume that the pressure in the hot and the cold phases is balanced at the first order phase transition point. This suggests that the reweighting method with two parameters is applicable in a wide range for the purpose of tracing out the phase transition line in the parameter space. To confirm the usefulness of the reweighting method for two-flavor QCD, the fluctuations of the reweighting factor are measured by numerical simulations for the cases of reweighting in the quark mass and chemical potential directions. The relation to the phase transition line is discussed. Moreover, the sign problem caused by the complex phase fluctuations is studied.

    DOI: 10.1103/PhysRevD.69.094506

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  • Numerical study of the equation of state for two flavor QCD at finite density Reviewed

    S Ejiri, CR Allton, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    INTERNATIONAL CONFERENCE ON COLOR CONFINEMENT AND HADRONS IN QUANTUM CHROMODYNAMICS   408 - 412   2004.5

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    We discuss the equation of state for 2 flavor QCD at non-zero temperature and density. Derivatives of In Z with respect to quark chemical potential mu(q) up to fourth order are calculated, enabling estimates of the pressure, quark number density and associated susceptibilities as functions Of mu(q) via a Taylor series expansion. It is found that the fluctuations in the quark number density increase in the vicinity of the phase transition temperature and the susceptibilities start to develop a pronounced peak as p. is increased. This suggests the presence of a critical endpoint in the (T, mu(q)) plane.

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  • The equation of state for two flavor QCD at finite density Reviewed

    S Ejiri, CR Allton, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   129   545 - 547   2004.3

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    We discuss the equation of state for QCD at non-zero temperature and density. We present, results of a simulation for QCD with 2 flavors of p4-improved staggered fermions. Derivatives of In Z with respect to quark chemical potential mu(q) up to fourth order are calculated, enabling estimates of the pressure, quark number density and associated susceptibilities as functions of mu(q) via a Taylor series expansion. We also discuss the radius of convergence of the expansion as a function of temperature. It, is found that the fluctuations in the quark number density increase in the vicinity of the phase transition temperature and the susceptibilities start to develop a pronounced peak as mu(q), is increased. This suggest's the presence of a critical endpoint in the (T, mu(q)) plane.

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  • Where is the chiral critical point in 3-flavor QCD? Reviewed

    F Karsch, CR Allton, S Ejiri, SJ Hands, O Kaczmarek, E Laermann, C Schmidt

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   129   614 - 616   2004.3

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    We determine the location of the second order endpoint of the line of first order chiral phase transition in 3-flavor QCD at vanishing chemical potential (mu(q)). Using Ferrenberg-Swendsen reweighting for two values of the quark mass we determine the mu(q)-dependence of the transition line and locate the chiral critical point. For both quantities we find a significant quark mass dependence.

    DOI: 10.1016/j.nuclphysbps.2003.12.236

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  • Heavy quark free energies and the renormalized Polyakov loop in full QCD Reviewed

    O Kaczmarek, S Ejiri, F Karsch, E Laermann, F Zantow

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   153 ( 153 )   287 - 294   2004.1

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    We study the renormalized free energy of a heavy quark anti-quark pair in the different colour channels in full QCD at finite temperature. Similarities and differences to the quenched case are discussed and the temperature dependence as well as their short distance behavior are analyzed. The asymptotic large distance behavior of the free energy is used to define the non-perturbatively renormalized Polyakov loop which is well behaved in the continuum limit.

    DOI: 10.1143/PTPS.153.287

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  • Lattice simulations of 2-colour QCD with Wilson fermions Reviewed

    JI Skullerud, S Ejiri, S Hands, L Scorzato

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   153 ( 153 )   60 - 68   2004.1

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    We report on the status of our simulations of two-colour QCD with two flavours of Wilson quarks, at nonzero chemical potential and diquark source. Preliminary results are presented for the static quark potential, gluon propagator, and meson and diquark spectrum.

    DOI: 10.1143/PTPS.153.60

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  • Study of QCD thermodynamics at finite density by Taylor expansion. Reviewed

    S Ejiri, CR Allton, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   153 ( 153 )   118 - 126   2004.1

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    We discuss the phase structure and the equation of state for QCD at non-zero temperature and density. Derivatives of ln Z with respect to quark chemical potential mu(q) up to fourth order are calculated for 2-flavor QCD, enabling estimates of the pressure, quark number density and associated susceptibilities as functions of mu(q) via a Taylor series expansion. Also, the phase transition line for 2 and 3-flavor QCD and the critical endpoint in the (T, mu(q)) plane are investigated in the low density regime.

    DOI: 10.1143/PTPS.153.118

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  • Calculation of nonleptonic kaon decay amplitudes from K -> pi matrix elements in quenched domain-wall QCD Reviewed

    J Noaki, S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, KI Nagai, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   68 ( 1 )   14501   2003.7

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    We explore the application of the domain wall fermion formalism of lattice QCD to calculate the K--&gt;pipi decay amplitudes in terms of the K+--&gt;pi(+) and K-0--&gt;0 hadronic matrix elements through relations derived in chiral perturbation theory. Numerical simulations are carried out in quenched QCD using the domain-wall fermion action for quarks and a renormalization group-improved gauge action for gluons on a 16(3)x32x16 and 24(3)x32x16 lattice at beta = 2.6 corresponding to the lattice spacing 1/a approximate to 2 GeV. Quark loop contractions which appear in Penguin diagrams are calculated by the random noise method, and the DeltaI = 1/2 matrix elements which require subtractions with the quark loop contractions are obtained with a statistical accuracy of about 10%. We investigate the chiral properties required of the K+--&gt;pi(+) matrix elements. Matching the lattice matrix elements to those in the continuum at mu = 1/a using the perturbative renormalization factor to one loop order, and running to the scale mu = m(c) = 1.3 GeV with the renormalization group for N-f = 3 flavors, we calculate all the matrix elements needed for the decay amplitudes. With these matrix elements, the DeltaI = 3/2 decay amplitude Re A(2) shows a good agreement with experiment after an extrapolation to the chiral limit. The DeltaI = 1/2 amplitude Re A(0), on the other hand, is about 50-60 % of the experimental one even after chiral extrapolation. In view of the insufficient enhancement of the DeltaI = 1/2 contribution, we employ the experimental values for the real parts of the decay amplitudes in our calculation of epsilon'/epsilon. The central values of our result indicate that the DeltaI = 3/2 contribution is larger than the DeltaI = 1/2 contribution so that epsilon'/epsilon is negative and has a magnitude of order 10(-4). We discuss in detail possible systematic uncertainties, which seem too large for a definite conclusion on the value of epsilon'/epsilon.

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  • Renormalization-group-improved action on anisotropic lattices Reviewed

    S Ejiri, K Kanaya, Y Namekawa, T Umeda

    PHYSICAL REVIEW D   68 ( 1 )   14502   2003.7

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    We study a block spin transformation in the SU(3) lattice gauge theory on anisotropic lattices to obtain Iwasaki's renormalization-group-improved action for anisotropic cases. For the class of actions with plaquette and 1x2 rectangular terms, we determine the improvement parameters as functions of the anisotropy xi = a(s)/a(t). We find that the program of improvement works well also on anisotropic lattices. From a study of an indicator which estimates the distance to the renormalized trajectory, we show that, for the range of the anisotropy xi approximate to 1-4, the coupling parameters previously determined for isotropic lattices improve the theory considerably.

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  • Remarks on the reweighting method in the chemical potential direction Reviewed

    S Ejiri

    STRONG AND ELECTROWEAK MATTER 2002, PROCEEDINGS   261 - 265   2003.6

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    We comment on the reweighting method in the chemical potential (mu(q)) direction. We study the fluctuation of the reweighting factor during Monte-Carlo steps. We find that it is the absolute value of the reweighting factor that mainly contributes to the shift of the phase transition line (beta(c)) by the presence of mu(q). The phase fluctuation is a cause of the sign problem, but the effect on beta(c) seems to be small. We also discuss beta(c), for lso-vector chemical potential and beta(c), determined from simulations with imaginary chemical potential.

    DOI: 10.1142/9789812704498_0025

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  • The quark mass and mu dependence of the QCD chiral critical point Reviewed

    C Schmidt, CR Allton, S Ejiri, SJ Hands, O Kaczmarek, F Karsch, E Laermann

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   119   517 - 519   2003.5

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    In order to study the QCD chiral critical point we investigate Binder Cumulants of the chiral condensate. The results were obtained from simulations of 3 and 2+1 flavors of standard staggered fermions and 3 flavors of p4 improved staggered fermions. The quark masses used are close to the physical quark mass. To extract the dependence on quark mass and chemical potential we apply a new reweighting technique based on a Taylor expansion of the action. The reweighting accuracy is 0(m) for the standard and O(m(2)), O(mu(2)) for the p4 action.

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  • The QCD phase transition at high temperature and low density Reviewed

    S Ejiri, CR Allton, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   119   538 - 540   2003.5

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    We study the thermal properties of QCD in the presence of a small quark chemical potential p. Derivatives of the phase transition point with respect to mu axe computed at mu = 0 for 2 and 3 flavors of p-4 improved staggered fermions on a 16(3) x 4 lattice. Moreover we contrast the case of isoscalar and isovector chemical potentials, quantify the effect of mu not equal 0 on the equation of state, and comment on the screening effect by dynamical quarks and the complex phase of the fermion determinant in QCD with mu not equal 0.

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  • Erratum: Light hadron spectroscopy with two flavors of dynamical quarks on the lattice [Phys. Rev. D65, 054505 (2002)] Reviewed

    A. Ali Khan, S. Aoki, G. Boyd, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Physical Review D   67 ( 5 )   059901   2003.3

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    DOI: 10.1103/physrevd.67.059901

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  • Light hadron spectrum and quark masses from quenched lattice QCD Reviewed

    S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   67 ( 3 )   34503   2003.2

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    We present the details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on lattices of size 32(3)x56-64(3)x112 at four values of lattice spacings in the range aapproximate to0.1-0.05 fm and spatial extent L(s)aapproximate to3 fm. Hadronic observables are calculated at five quark masses corresponding to m(PS)/m(V)approximate to0.75-0.4, assuming the u and d quarks are degenerate, but treating the s quark separately. We find that the presence of quenched chiral singularities is supported from an analysis of the pseudoscalar meson data. The physical values of hadron masses are determined using m(pi), m(rho), and m(K) (or m(phi)) as input to fix the physical scale of lattice spacing and the u, d, and s quark masses. After chiral and continuum extrapolations, the agreement of the calculated mass spectrum with experiment is at a 10% level. In comparison with the statistical accuracy of 1%-3% and systematic errors of at most 1.7% we have achieved, this demonstrates a failure of the quenched approximation for the hadron spectrum: the hyperfine splitting in the meson sector is too small, and in the baryon sector the octet masses and mass splitting of the decuplet are both smaller than experiment. Light quark masses are calculated using two definitions: the conventional one and the one based on the axial-vector Ward identity. The two results converge toward the continuum limit, yielding m(ud)=4.29(14)(-0.79)(+0.51) MeV where the first error is statistical and the second one is systematic due to chiral extrapolation. The s quark mass depends on the strange hadron mass chosen for input: m(s)=113.8(2.3)(-2.9)(+5.8) MeV from m(K) and m(s)=142.3(5.8)(-0)(+22.0) MeV from m(phi), indicating again a failure of the quenched approximation. We obtain the scale of QCD, Lambda((M) over bar)((0))=219.5(5.4) MeV with m(rho) used as input. An O(10%) deviation from experiment is observed in the pseudoscalar meson decay constants.

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  • Erratum: Dynamical Quark Effects on Light Quark Masses [Phys. Rev. Lett. 85, 4674 (2000)] Reviewed

    A. Ali Khan, S. Aoki, G. Boyd, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Physical Review Letters   90 ( 2 )   029902   2003.1

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    DOI: 10.1103/physrevlett.90.029902

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  • QCD thermal phase transition in the presence of a small chemical potential Reviewed

    CR Allton, S Ejiri, SJ Hands, O Kaczmarek, F Karsch, E Laermann, C Schmidt, L Scorzato

    PHYSICAL REVIEW D   66 ( 7 )   74507   2002.10

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    We propose a new method to investigate the thermal properties of QCD with a small quark chemical potential mu. Derivatives of quark and gluonic observables with respect to mu are computed at mu=0 for two flavors of p4 improved staggered fermions with ma=0.1,0.2 on a 16(3)x4 lattice, and used to calculate the leading order Taylor expansion in mu of the location of the pseudocritical point about mu=0. This expansion should be well behaved for the small values of mu(q)/T(c)similar to0.1 relevant for BNL RHIC phenomenology, and predicts a critical curve T-c(mu) in reasonable agreement with estimates obtained using exact reweighting. In addition, we contrast the case of isoscalar and isovector chemical potentials, quantify the effect of munot equal0 on the equation of state, and comment on the complex phase of the fermion determinant in QCD with munot equal0.

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  • Scaling laws and effective dimension in latticeSU(2)Yang-Mills theory with a compactified extra dimension Reviewed

    Shinji Ejiri, Shouji Fujimoto, Jisuke Kubo

    Physical Review D   66 ( 3 )   036002   2002.8

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    Monte Carlo simulations are performed in a five-dimensional lattice SU(2) Yang-Mills theory with a compactified extra dimension, and scaling laws are studied. Our simulations indicate that, as the compactification radius R decreases, the confining phase spreads more and more to the weak coupling regime, and the effective dimension of the theory changes gradually from five to four. Our simulations also indicate that the limit a(4)--&gt;0 with R/a(4) kept fixed exists in both the confining and deconfining phases if R/a(4) is small enough, where a(4) is the lattice spacing in the four-dimensional direction. We argue that there exists a maximal radius above which the color degrees of freedom are not confined. Comments on deconstructing extra dimensions are given.

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  • Charmonium spectrum from quenched anisotropic lattice QCD Reviewed

    M Okamoto, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, KI Ishikawa, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, K Nagai, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   65 ( 9 )   94508   2002.5

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    We present a detailed study of the charmonium spectrum using anisotropic lattice QCD. We first derive a tree-level improved clover quark action on the anisotropic lattice for arbitrary quark mass by matching the Hamiltonian on the lattice and in the continuum. The heavy quark mass dependence of the improvement coefficients, i.e., the ratio of the hopping parameters zeta=K-t/K-s and the clover coefficients c(s,t), is examined at the tree level, and effects of the choice of the spatial Wilson parameter r(s) are discussed. We then compute the charmonium spectrum in the quenched approximation employing xi=a(s)/a(t)=3 anisotropic lattices. Simulations are made with the standard anisotropic gauge action and the anisotropic clover quark action with r(s)=1 at four lattice spacings in the range a(s)=0.07-0.2 fm. The clover coefficients c(s,t) are estimated from tree-level tadpole improvement. On the other hand, for the ratio of the hopping parameters zeta, we adopt both the tree-level tadpole-improved value and a non-perturbative one. The latter employs the condition that the speed of light calculated from the meson energy-momentum relation be unity. We calculate the spectrum of S and P states and their excitations using both the pole and kinetic masses. We find that the combination of the pole mass and the tadpole-improved value of zeta to yield the smoothest approach to the continuum limit, which we then adopt for the continuum extrapolation of the spectrum. The results largely depend on the scale input even in the continuum limit, showing a quenching effect. When the lattice spacing is determined from the 1P-1S splitting, the deviation from the experimental value is estimated to be similar to30% for the S-state hyperfine splitting and similar to20% for the P-state fine structure. Our results are consistent with previous results at xi=2 obtained by Chen when the lattice spacing is determined from the Sommer scale r(0). We also address the problem with the hyperfine splitting that different choices of the clover coefficients lead to disagreeing results in the continuum limit. Making a leading order analysis based on potential models we show that a large hyperfine splitting similar to95 MeV obtained by Klassen with a different choice of the clover coefficients is likely an overestimate.

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  • QCD at nonzero chemical potential and temperature from the lattice Reviewed

    C.R. Allton, S. Ejiri, S.J. Hands, O. Kaczmarek, F. Karsch, E. Laermann, C. Schmidt, L. Scorzato

    Joint CCSM/JHF/NITP Workshop on Physics at the Japan Hadron Facility, Adelaide   2002.3

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  • Calculation of K -&gt; pi pi decay amplitudes from K -&gt; pi matrix elements in quenched domain-wall QCD Reviewed

    S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, KI Nagai, J Noaki, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   332 - 334   2002.3

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    we present a calculation of the K --&gt; pipi decay amplitudes from the K --&gt; pi matrix elements using leading order relations derived in chiral perturbation theory. Numerical simulations are carried out in quenched QCD with the domain-wall fermion action and the renormalization group improved gluon action. Our results show that the I = 2 amplitude is reasonably consistent with experiment whereas the I = 0 amplitude is sizably smaller. Consequently the DeltaI = 1/2 enhancement is only half of the experimental value, and epsilon'/epsilon is negative.

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  • Non-perturbative renormalization in domain-Wall QCD by Schrodinger functional scheme Reviewed

    S Aoki, Y Aoki, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   844 - 846   2002.3

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    We formulate and numerically test the Schrodinger functional scheme for domain-wall QCD. We then apply it to a non-perturbative calculation of the renormalization factors for vector and axial-vector currents in quenched domain-wall QCD with plaquette and renormalization group improved gauge actions at a(-1) similar or equal to 2 GeV.

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  • Equation of state for pure SU(3) gauge theory on anisotropic lattices Reviewed

    S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, Y Namekawa, M Okamoto, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   477 - 479   2002.3

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    We present results for the equation of state for pure SU(3) gauge theory obtained on anisotropic lattices with the anisotropy xi equivalent to a(s)/a(t) = 2. The pressure and energy density are calculated on N-t/xi = 4,5 and 6 lattices with the integral method. They are found to satisfy the leading 1/N-t(2) scaling from our coarsest lattice N-t/xi = 4. This enables us to carry out well controlled continuum extrapolations. We find that the pressure and energy density agree with those obtained using the isotropic plaquette action, but have smaller and more reliable errors.

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  • Aspects of the thermal phase transition of QCD with small chemical potential Reviewed

    S Ejiri, CR Allton, SJ Hands, O Kaczmarek, F Karsch, E Laermann, L Scorzato

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   459 - 461   2002.3

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    We propose a new method to investigate the thermal properties of QCD with a small chemical potential (mu). The derivatives of the phase transition point with respect to a are computed for 2 flavors of p4-improved staggered fermions. We moreover comment on the complex phase of the fermion determinant in finite-density QCD.

    DOI: 10.1016/S0920-5632(01)01746-7

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  • Charmonium spectrum from quenched QCD on anisotropic lattices Reviewed

    S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, K Nagai, M Okamoto, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   364 - 366   2002.3

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    We present our final results of the charmonium spectrum in quenched QCD on anisotropic lattices. Simulations are made with the plaquette gauge action and a tadpole improved clover quark action employing xi = a(3)/a(t) = 3. We calculate the spectrum of S- and P-states and their excitation, and study the scaling behavior of mass splittings. Comparison is made with the experiment and previous lattice results. The issue of hyperfine splitting for different choices of the clover coefficients obtained by Klassen is discussed.

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  • Chiral property of domain-wall fermion from eigenvalues of 4D Wilson-Dirac operator Reviewed

    S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, Lesk, V, KI Nagai, M Okawa, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   106   718 - 720   2002.3

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    We investigate a chiral property of the domain-wall fermion (DWF) system using the four-dimensional hermitian Wilson-Dirac operator H-W. A formula expressing the Ward-Takahashi identity quark mass m(5q) with eigenvalues of this operator is derived, which well explains the N-5 dependence of m(5q) observed in previous numerical simulations. We further discuss the chiral property of DWF in the large volume in terms of the spectra of H-W.

    DOI: 10.1016/S0920-5632(01)01826-6

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  • Light hadron spectroscopy with two flavors of dynamical quarks on the lattice Reviewed

    AA Khan, S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   65 ( 5 )   054505   2002.3

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    We present results of a numerical calculation of lattice QCD with two degenerate flavors of dynamical quarks, identified with up and down quarks, and with a strange quark treated in the quenched approximation. The lattice action and simulation parameters are chosen with a view to carrying out an extrapolation to the continuum limit as well as chiral extrapolations in dynamical up and down quark masses. Gauge configurations are generated with a renormalization-group improved gauge action and a mean field improved clover quark action at three values of beta = 6/g(2), corresponding to lattice spacings of aapproximate to0.22, 0.16 and 0.11 fm, and four sea quark masses corresponding to m(PS)/m(V)approximate to0.8, 0.75, 0.7 and 0.6. The sizes of lattice are chosen to be 123 x 24, 16(3) x 32 and 24(3) x 48 so that the physical spatial size is kept constant at Laapproximate to2.5 fm. Hadron masses, light quark masses and meson decay constants are measured at five valence quark masses corresponding to m(PS)/m(V)approximate to0.8, 0.75, 0.7, 0.6 and 0.5. We also carry out complementary quenched simulations with the same improved actions. The quenched spectrum from this analysis agrees well in the continuum limit with the one of our earlier work using the standard action, quantitatively confirming the systematic deviation of the quenched spectrum from experiment, We find the two-flavor full QCD meson masses in the continuum limit to be much closer to experimental meson masses than those from quenched QCD. When using the K meson mass to fix the strange quark mass, the difference between quenched QCD and experiment of 2.6(-0.9)(+0.3)% for the K* meson mass and of 4.1(-1.6)(+0.5)% for the phi meson mass is reduced to 0.7(-1.7)(+1.1)% and 1.3(-2.5)(+1.8)% in full QCD, where the errors include estimates of systematic errors of the continuum extrapolation as well as statistical errors. Analyses of the J parameter yield a similar trend in that the quenched estimate in the continuum limit J =0.375(-0.009)(+0.039) increases to J=0.440(-0.031)(+0.061) in two-flavor full QCD, approaching the experimental value J approximate to0.48. We take these results as manifestations of sea quark effects in two-flavor full QCD. For baryon masses full QCD values for strange baryons such as Xi and Omega are in agreement with experiment, while they differ increasingly with decreasing strange quark content, resulting in a nucleon mass higher than experiment by 10% and a Delta mass by 13%. The pattern suggests finite size effects as -a passible origin for this deviation. For light quark masses in the continuum limit we obtain in m(ud)((MS) over bar)(2 GeV) = 3.44(-0.22)(+0.14) MeV and m(s)((MS) over bar) (2 GeV) =88(-6)(+4) MeV (K-input) and m(s)(MS) over bar (2 GeV) = 90(-11)(+5) MeV (phi-input), which are reduced by about 25% compared to the values in quenched QCD. We also present results for decay constants where large scaling violations obstruct a continuum extrapolation, The need for a nonperturbative estimate of renormalization factors is discussed.

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  • Kaon B parameter from quenched domain-wall QCD Reviewed

    AA Khan, S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, KI Nagai, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   64 ( 11 )   114506   2001.12

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    We report on a calculation of B-K with domain-wall fermion action in quenched QCD. Simulations are made with a renormalization group improved gauge action at beta = 2.6 and 2.9 corresponding to a(-1) approximate to 2 and 3 GeV. Effects, due to finite fifth dimensional size N-5 and finite spatial size N-sigma are examined in detail. Matching to the continuum operator is made perturbatively at one loop order. We obtain B-K(mu = 2 GeV) = 0.5740(61)(191), where the first error is statistical and the second error represents an estimate of scaling violation and O(alpha (2)) errors in the renormalization factor added in quadrature, as an estimate of the continuum value in the modified minimal subtraction ((MS) over bar) scheme with naive dimensional regularization. This value is consistent, albeit somewhat small, with B-K(mu = 2 GeV) = 0.068(42) obtained b the JLQCD Collaboration using the Kogut-Susskind quark action. Results for light quark masses are also reported.

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  • Topological susceptibility in lattice QCD with two flavors of dynamical quarks Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   64 ( 11 )   114501   2001.12

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    We present a study of the topological susceptibility in lattice QCD with two degenerate flavors of dynamical quarks. The topological charge is measured on gauge configurations generated with a renormalization group improved gauge action and a mean held improved clover quark action at three values of beta = 6/g(2) with four sea quark masses at each beta. The lattice spacings at these beta 's are a approximate to 0.22, 0.16 and 0.11 fm at the physical up and down quark mass, which are fixed by the physical rho meson mass. The study is supplemented by simulations of pure SU(3) gauge theory with the same gauge action at 5 values of beta with lattice spacings 0.09 fm less than or similar toa less than or similar to0.27 fm. We employ a field-theoretic definition of the topological charge together with cooling. For the topological susceptibility in the continuum limit of pure SU(3) gauge theory we obtain chi (1/4)(t) = 197(-16)(+13) MeV where the error shows statistical and systematic ones added in quadrature, In full QCD chi (t) at heavy sea quark masses is consistent with that of pure SU(3) gauge theory. A decrease of chi (t) toward light quark masses, as predicted by the anomalous Ward-Takahashi identity for U(1) chiral symmetry, becomes clearer for smaller lattice spacings. The cross over in the behavior of chi (t) from heavy to light sea quark masses is discussed.

    DOI: 10.1103/PhysRevD.64.114501

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  • Hybrid quarkonia with dynamical sea quarks Reviewed

    T. Manke, A. Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Physical Review D   64 ( 9 )   097505 - 97505   2001.10

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    DOI: 10.1103/physrevd.64.097505

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  • Equation of state in finite-temperature QCD with two flavors of improved Wilson quarks Reviewed

    A. Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. I. Nagai, M. Okamoto, M. Okawa, H. P. Shanahan, Y. Taniguchi, A. Ukawa, T. Yoshié

    Physical Review D   64 ( 7 )   74510   2001.9

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    We present the results of a first study of the equation of state in finite-temperature QCD with two flavors of Wilson-type quarks. The simulations are made on lattices with a temporal size Nt=4 and 6, using a renormalization-group-improved action for the gluon sector and a mean-field-improved clover action for the quark sector. The lines of constant physics corresponding to fixed values of the ratio mPS/mV of the pseudoscalar to vector meson masses at zero temperature are determined, and the beta functions which describe the renormalization-group flow along these lines are calculated. Using these results, the energy density and the pressure are calculated as functions of temperature along the lines of constant physics in the range mPS/mV =0.65-0.95. The quark mass dependence in the equation of state is found to be small for mPS/mV≲0.8. A comparison of the results for Nt=4 and Nt=6 lattices shows a significant scaling violation present in the Nt=4 results. At high temperatures the results for Nt=6 are quite close to the continuum Stefan-Boltzmann limit, suggesting the possibility of a precise continuum extrapolation of thermodynamic quantities from simulations at Nt≳6. © 2001 The American Physical Society.

    DOI: 10.1103/PhysRevD.64.074510

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  • Thermodynamics of SU(3) gauge theory on anisotropic lattices Reviewed

    Y. Namekawa, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, V. Lesk, M. Okamoto, M. Okawa, Y. Taniguchi, A. Ukawa, T. Yoshié

    Physical Review D   64 ( 7 )   74507 - 7450713   2001.9

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    Finite temperature SU(3) gauge theory is studied on anisotropic lattices using the standard plaquette gauge action. The equation of state is calculated on 163×8, 203×10, and 243×12 lattices with the anisotropy ξ ≡as/at=2, where as and at are the spatial and temporal lattice spacings. Unlike the case of the isotropic lattice on which Nt=4 data deviate significantly from the leading scaling behavior, the pressure and energy density on an anisotropic lattice are found to satisfy well the leading 1/Nt2 scaling from our coarsest lattice Nt/ξ=4. With three data points at Nt/ξ=4, 5 and 6, we perform a well controlled continuum extrapolation of the equation of state. Our results in the continuum limit agree with a previous result from isotropic lattices using the same action, but have smaller and more reliable errors. © 2001 The American Physical Society.

    DOI: 10.1103/PhysRevD.64.074507

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  • Bmeson decay constants from two-flavor lattice QCD with nonrelativistic heavy quarks Reviewed

    A. Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Physical Review D   64 ( 5 )   054504   2001.8

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    DOI: 10.1103/physrevd.64.054504

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  • Decay constants of B and D mesons from improved relativistic lattice QCD with two flavors of sea quarks Reviewed

    Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Ivvasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshie

    Physical Review D   64 ( 3 )   34505   2001.7

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    We present a calculation of the B and D meson decay constants in lattice QCD with two (Nf=2) flavors of light dynamical quarks, using an 0(a)-improved Wilson action for both light and heavy quarks and a renormalization-group improved gauge action. Simulations are made at three values of lattice spacing a = 0.22,0.16,0.11 fm and four values of sea quark mass in the range mPS/invO.S- 0.6. Our provisional estimate for the continuum values of the decay constants are fBd = 208(10)(29) MeV, fBs = 250(10)(35)(-0 +8) MeV,fDd=225(14)(40) MeV,fDj=267(13)(48)(°) MeV for Nf=2 where the statistical and systematic errors are separately listed, and the third error for/Bj and/Dj shows the uncertainty of the determination of the strange quark mass. We also carry out a set of quenched simulations using the same action to make a direct examination of sea quark effects. Taking the ratio of results for Nf=2 and Af=0, we obtain fbd Nf=2/2T°=1.11(6)£r 2//£f°= U4(5)4r11°= l.03(6)4f 2/£f °= 1.07(5). They show a 10-15% increase in the Nf=2 results over those of Nj=Q for the B meson decay constants, while evidence for such a trend is statistically less clear for the D meson decay constants. ©2001 The American Physical Society.

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  • Chiral properties of domain-wall quarks in quenched QCD Reviewed

    A. Ali Khan, S. Aoki, Y. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, T. Izubuchi, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. I. Nagai, J. Noaki, M. Okawa, H. P. Shanahan, Y. Taniguchi, A. Ukawa, T. Yoshié

    Physical Review D   63 ( 11 )   114504 - 114504   2001.5

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    DOI: 10.1103/physrevd.63.114504

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  • Lattice QCD at finite temperature Reviewed

    S Ejiri

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   19 - 26   2001.3

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    Recent developments in finite-temperature QCD with dynamical quarks are reviewed focusing on the topics of critical temperature, the equation of state, and critical behaviors around the chiral phase transition.

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  • Eigenvalues of the hermitian Wilson-Dirac operator and chiral properties of the domain-wall fermion Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kanebo, Y Kuramashi, T Manke, KI Nagai, J Noaki, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   725 - 728   2001.3

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    Chiral properties of QCD formulated with the domain-wall fermion (DWQCD) are studied using the anomalous quark mass ms, and the spectrum of the l-dimensional Wilson-Dirac operator. Numerical simulations are made with the standard plaquette gauge action and a renormalization-group improved gauge action. Results are reported on the density of zero eigenvalue obtained with the accumulation method, and a comparison is made with the results for m(5q).

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  • Calculation of K -&gt; pi matrix elements in quenched domain-wall QCD Reviewed

    AA Khan, S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, KI Nagai, J Noaki, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   283 - 286   2001.3

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    We explore the possibility for an evaluation of non-leptonic DeltaS = 1 K decay amplitudes through the calculation of K --&gt; pi matrix elements using domain-wall QCD. The relation between the physical K --&gt; pi pi matrix elements and K --&gt; pi matrix elements deduced from chiral perturbation theory is recapitulated. Quenched numerical simulations are performed on an 16(3) x 32 x 16 lattice at a lattice spacing a(-1) approximate to 2GeV for both the standard plaquette gauge action and a renormalization-group improved gauge action, and reasonable signals for K --&gt; pi matrix elements are obtained. Preliminary results are reported on the K --&gt; pi pi matrix elements, and results from two actions are compared.

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  • Full QCD light hadron spectrum and quark masses: Final results from CP-PACS Reviewed

    AA Khan, S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, KI Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   229 - 232   2001.3

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    We present the final results of the CP-PACS calculation of the light hadron spectrum and quark masses with two flavors of dynamical quarks. Simulations are made with a renormalization-group improved gauge action and a mean-field improved clover quark action for sea quark masses corresponding to m(PS)/m(V) approximate to 0.8-0.6 and the lattice spacing a 0.22-0.11 fm. For the meson spectrum in the continuum limit a clearly improved agreement with experiment is observed compared to the quenched case, demonstrating the importance of sea quark effects. For light quark masses we obtain m(ud)((MS) over bar)(2GeV) = 3.44(-0.22)(+0.14) MeV and m(s)((MS) over bar) (2GeV) = 88(-6)(+4) MeV (K-input) and m(s)((MS) over bar) (2GeV) = 90(-11)(+5) MeV (phi -input), which are reduced by about 25% compared to the values in quenched QCD.

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  • Quenched charmonium spectrum on anisotropic lattices Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, KI Nagai, M Okamoto, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   325 - 328   2001.3

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    We present the results of quenched charmonium spectrum for S- and P-states, obtained by a relativistic heavy quark method on anisotropic lattices. Simulations are carried out using the standard plaquette gauge action and a meanfield-improved clover quark action at a(t)(-1) = 3-6 GeV with the renormalized anisotropy fixed to xi drop a(s)/a(t) = 3. We study the scaling of our fine and hyperfine mass splittings, and compare with previous results.

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  • Kaon B-parameter from quenched domain-wall QCD Reviewed

    AA Khan, S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fikugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, KI Nagai, J Noaki, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   94   287 - 290   2001.3

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    We report on a calculation of B-K with domain wall fermion action in quenched QCD. Simulations are made with a renormalization group improved gauge action at beta = 2.6 and 2.9 corresponding to a(-1) approximate to 2GeV and 3GeV. Effects due to finite fifth dimensional size N-5 and finite spatial size N-sigma are examined in detail. Matching to the continuum operator is made perturbatively at one loop order. We obtain B-K (mu = 2GeV) = 0.5746(61), where the error is statistical only, as an estimate of the continuum value in the (MS) over bar scheme with naive dimensional regularization. This value is smaller but consistent with B-K (mu = 2GeV) = 0.628(42) obtained by the JLQCD Collaboration using the Kogut-Susskind quark action. Results for strange quark mass are also reported.

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  • Light hadron spectrum from quenched lattice QCD: Results from the CP-PACS Reviewed

    Tomoteru Yoshié, A. Ali Khan, S. Aoki, G. Boyd, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Progress of Theoretical Physics   105 ( 1 )   37 - 75   2001.1

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    Deriving the light hadron spectrum from first principles of QCD has been a fundamental issue in elementary particle physics since the mid-1970s, when QCD was established. With this goal in mind, we have carried out large-scale simulations of lattice QCD on the CP-PACS computer. In this article, we present results for the light hadron spectrum derived in the quenched approximation to lattice QCD. We find that although the global structure of the observed spectrum is reproduced, the quenched spectrum systematically deviates from experiment when examined with an accuracy at better than a 10% level. Results for light quark masses are also reported. Another simulation of full QCD done recently (also on the CP-PACS computer) shows indications that the discrepancy observed in quenched QCD is significantly reduced by the introduction of two flavors of light dynamical quarks.

    DOI: 10.1143/PTP.105.37

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  • Phase structure and critical temperature of two-flavor QCD with a renormalization group improved gauge action and clover improved Wilson quark action Reviewed

    A. Ali Khan, CP-PACS Collaboration, R. Burkhalter, S. Ejiri, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Manke, K. Nagai, A. Ukawa, T. Yoshié, S. Aoki, R. Burkhalter, N. Ishizuka, Y. Iwasaki, K. Kanaya, M. Okamoto, A. Ukawa, T. Yoshié, M. Fukugita, S. Hashimoto, T. Kaneko, M. Okawa, Y. Kuramashi

    Physical Review D   63 ( 3 )   34502   2000.12

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    We study the finite-temperature phase structure and the transition temperature of QCD with two flavors of dynamical quarks on a lattice with the temporal size Nt=4, using a renormalization group improved gauge action and the Wilson quark action improved by the clover term. The region of a parity-broken phase is identified, and the finite-temperature transition line is located on a two-dimensional parameter space of the coupling (β=6/g2) and hopping parameter K. Near the chiral transition point, defined as the crossing point of the critical line of the vanishing pion mass and the line of finite-temperature transition, the system exhibits behavior well described by the scaling exponents of the three-dimensional O(4) spin model. This indicates a second-order chiral transition in the continuum limit. The transition temperature in the chiral limit is estimated to be Tc=171(4) MeV. © 2000 The American Physical Society.

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  • Sea quark effects on quarkonia Reviewed

    T. Manke, A. Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, K. Nagai, M. Okawa, H. P. Shanahan, A. Ukawa, T. Yoshié

    Physical Review D   62 ( 11 )   114508 - 114508   2000.11

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    DOI: 10.1103/physrevd.62.114508

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  • Dynamical quark effects on light quark masses Reviewed

    AA Khan, S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW LETTERS   85 ( 22 )   4674 - 4677   2000.11

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    Light quark masses are calculated in lattice QCD with two degenerate flavors of dynamical quarks. The calculations are made with improved actions with lattice spacing a = 0.22-0.11 fm. In the continuum limit we find m(ud)((M) over barS) (2 GeV) =3.44(-0.22)(+0.14)MEV using the pi and rho meson masses as physical input, uum limit we find m,d and m(s) ((M) over barS)(2 GeV) = 88(-6)(+4) MeV or 90(-11)(+5) MeV with the K or phi meson mass as additional input. The quoted errors represent statistical and systematic combined, the latter including those from continuum and chiral extrapolations, and from renormalization factors. Compared to quenched results, two flavors of dynamical quarks reduce quark masses by about 25%.

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  • Study on the nonperturbative existence of Yang-Mills theories with large extra dimensions Reviewed

    Shinji Ejiri, Jisuke Kubo, Michika Murata

    Physical Review D   62 ( 10 )   105025 - 105025   2000.10

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    DOI: 10.1103/physrevd.62.105025

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  • Eta meson mass and topology in QCD with two light flavors Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   162 - 164   2000.4

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    We present results for the mass of the flavor singlet meson calculated on two-flavor full QCD configurations generated by the CP-PACS full QCD project. We also investigate topological charge fluctuations and their dependence on the sea quark mass.

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  • Heavy-light spectrum and decay constant from NRQCD with two flavors of dynamical quarks Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   265 - 267   2000.4

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    We report on a study of B mesons on N-f = 2 full QCD configurations using an RG-improved gauge action, NRQCD heavy quark action and tadpole-improved clover light quark action. Results on the heavy-light spectrum and the decay constants from 16(3) x 32 lattices at a(-1) approximate to 1.5 GeV are presented, and compared with quenched results obtained with the same action combination at matching lattice spacings.

    DOI: 10.1016/S0920-5632(00)91642-6

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  • Heavy quarkonia from anisotropic and isotropic lattices Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   319 - 321   2000.4

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    We report on recent results for the spectrum of heavy quarkonia. Using coarse and anisotropic lattices we achieved an unprecedented control over statistical and systematic errors for higher excited states such as exotic hybrid states. In a parallel study on isotropic lattices we also investigate the effect of two dynamical flavours on the spin structure of charmonium and bottomonium for several symmetric lattices.

    DOI: 10.1016/S0920-5632(00)91660-8

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  • Heavy-light decay constants from clover heavy quark action in QCD with two flavors of dynamical quarks Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   331 - 333   2000.4

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    We present results on an analysis of the decay constants f(Bd) and f(Bs) with two flavours of sea quark. The calculation has been carried out on 3 different bare gauge couplings and 4 sea quark masses at each gauge coupling, with m(pi)/m(rho), ranging from 0.8 to 0.6. We employ the Fermilab formalism to perform calculations with heavy quarks whose mass is in the range of the b-quark. A detailed comparison with a quenched calculation using the same action is made to elucidate the effects due to the sea quarks.

    DOI: 10.1016/S0920-5632(00)91664-5

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  • Light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks Reviewed

    AA Khan, S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   176 - 178   2000.4

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    We present updated results of the CP-PACS calculation of the light hadron spectrum in N-f = 2 full QCD. Simulations are made with an RG-improved gauge action and a tadpole-improved clover quark action for sea quark masses corresponding to m(PS)/m(V) approximate to 0.8-0.6 and the lattice spacing a = 0.22-0.09 fm. A comparison of the N-f = 2 QCD spectrum with new quenched results, obtained with the same improved action, shows clearly the existence of sea quark effects in vector meson masses. Results for Light quark masses are also presented.

    DOI: 10.1016/S0920-5632(00)91615-3

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  • Equation of state for SU(3) gauge theory with RG improved action Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okamoto, M Okawa, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   384 - 386   2000.4

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    We present results for the equation of state for pure SU(3) gauge theory obtained with a renormalization-group (RG) improved action. The energy density and pressure are calculated on a 16(3) x 4 and a 32(3) x 8 lattice employing the integral method. Extrapolating the results to the continuum limit, we find the energy density and pressure to be in good agreement with those obtained with the standard plaquette action within the error of 3-4%.

    DOI: 10.1016/S0920-5632(00)91681-5

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  • Equation of state in finite-temperature QCD with improved Wilson quarks Reviewed

    AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okamoto, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   360 - 362   2000.4

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    We study finite-temperature phase transition and equation of state for two-flavor QCD at N-t = 4 using an RG-improved gauge action and a meanfield-improved clover quark action. The pressure is computed using the integral method. The O(4) scaling of chiral order parameter is also examined.

    DOI: 10.1016/S0920-5632(00)91673-6

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  • Quenched QCD with domain-wall fermions on coarse lattices Reviewed

    AA Khan, S Aoki, Y Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, T Izubuchi, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, HP Shanahan, Y Taniguchi, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   83-4   591 - 593   2000.4

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    We investigate the existence of chiral zero modes at a(-1) similar or equal to 1 GeV in quenched domain-wall QCD. Simulations are carried out for the plaquette and an RG-improved gauge actions on a 12(3) x 24 x N-s lattice with N-s = 10 - 50. We find that the pion mass in the chiral limit remains non-vanishing as N-s --&gt; infinity for both gauge actions. Possible origins of this non-vanishing pion mass are discussed.

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  • Quenched light hadron spectrum Reviewed

    S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW LETTERS   84 ( 2 )   238 - 241   2000.1

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    We present results of a large-scale simulation for the flavor nonsinglet light hadron spectrum in quenched lattice QCD with the Wilson quark action. Hadron masses are calculated ai four values of lattice spacing in the range a approximate to 0.1-0.05 fm on lattices with a physical extent of 3 fm five quark masses corresponding to m(pi)/m(rho) = 0.75-0.4. The calculated spectrum in the continuum limit shows a systematic deviation from experiment, though the magnitude of deviation is contained within 11%. Results for decay constants and light quark masses are also reported.

    DOI: 10.1103/PhysRevLett.84.238

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  • Equation of state for pure SU(3) gauge theory with renormalization group improved action Reviewed

    M. Okamoto, A. Ali Khan, S. Aoki, R. Burkhalter, S. Ejiri, M. Fukugita, S. Hashimoto, N. Ishizuka, Y. Iwasaki, K. Kanaya, T. Kaneko, Y. Kuramashi, T. Manke, K. Nagai, M. Okawa, A. Ukawa, T. Yoshié

    Physical Review D - Particles, Fields, Gravitation and Cosmology   60 ( 9 )   94510   1999.10

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    A lattice study of the equation of state for pure SU(3) gauge theory using a renormalization-group (RG) improved action is presented. The energy density and pressure are calculated on a (Formula presented) and a (Formula presented) lattice employing the integral method. Extrapolating the results to the continuum limit, we find the energy density and pressure to be in good agreement with those obtained with the standard plaquette action within the error of 3–4 %. © 1999 The American Physical Society.

    DOI: 10.1103/PhysRevD.60.094510

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  • Hybrid quarkonia on asymmetric lattices Reviewed

    T Manke, HP Shanahan, AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, A Ukawa, T Yoshie

    PHYSICAL REVIEW LETTERS   82 ( 22 )   4396 - 4399   1999.5

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    We report on a study of heavy quark bound states containing an additional excitation of the gluonic degrees of freedom. To this end we employ the nonrelativistic QCD approach on coarse and asymmetric lattices, where we discard vacuum polarization effects and neglect all spin-correction terms. We find a clear hybrid signal on all our lattices (a(s) = 0.15,..., 0.47 fm). We have studied in detail the lattice spacing artifacts, finite volume effects,and mass dependence. Within the above approximations we predict the lowest lying hybrid excitation in charmonium to be 1.323(13) GeV above the ground state, where we use the 1P-1S splitting to set the scale. The bottomonium hybrid was found to be 1.542(8) GeV above its ground state. [S0031-9007(99)09172-3].

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  • Heavy quark physics in N-f=2 QCD Reviewed

    S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   73 ( 1-3 )   375 - 377   1999.3

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    We present a preliminary analysis of the heavy-heavy spectrum and heavy-light decay constants in full QCD, using a tadpole-improved SW quark action and an RG-improved gauge action on a 16(3) x 32 lattice with four sea quark masses corresponding to m(pi)/m(p) approximate to 0.8, 0.75, 0.7, 0.6 and a(-1) approximate to 1.3 GeV. We focus particularly on the effect of sea quarks on these observables.

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  • Full QCD light hadron spectrum from the CP-PACS Reviewed

    S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   73   192 - 194   1999.3

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    We report on an on-going two-flavor full QCD study on CP-PACS using an RG-improved gauge action and a tadpole-improved SW quark action. Runs are made for three lattice spacings a(-1) approximate to 0.9, 1.3, and 2.5 GeV on 12(3) x 24, 16(3) x 32, and 24(3) x 48 lattices. Four sea quark masses having m(PS)/m(V) approximate to 0.8-0.6 are simulated, for each of which hadron masses are evaluated for valence quark masses corresponding to m(PS)/m(V) approximate to 0.8-0.5. Results for hadron and light quark masses are presented and compared with those obtained in quenched QCD.

    DOI: 10.1016/S0920-5632(99)85019-1

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  • The static quark potential in full QCD Reviewed

    S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   73   216 - 218   1999.3

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    We report results on the static quark potential in two-flavor full QCD. The calculation is performed for three values of lattice spacing a(-1) approximate to 0.9, 1.3 and 2.5 GeV on 12(3) x 24, 16(3) x 32 and 24(3) x 48 lattices respectively, at sea quark masses corresponding to m(pi)/m(p) approximate to 0.8-0.6. An RG-improved gauge action and a tadpole-improved SW clover quark action are employed. We discuss scaling of m(p)/root sigma and effects of dynamical quarks on the potential.

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  • Non-perturbative determination of anisotropy coefficients and pressure gap at the deconfining transition of QCD Reviewed

    S Ejiri, Y Iwasaki, K Kanaya

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   73   411 - 413   1999.3

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    We propose a new non-perturbative method to compute derivatives of gauge coupling constants with respect to anisotropic lattice spacings (anisotropy coefficients). Our method is based on a precise measurement of the finite temperature deconfining transition curve in the lattice coupling parameter space extended to anisotropic lattices by applying the spectral density method. We determine the anisotropy coefficients for the cases of SU(2) and SU(3) gauge theories. A longstanding problem, when one uses the perturbative anisotropy coefficients, is a nonvanishing pressure gap at the deconfining transition point in the SU(3) gauge theory. Using our non-perturbative anisotropy coefficients, we find that this problem is completely resolved.

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  • Quenched light hadron spectrum with the Wilson quark action: Final results from CP-PACS Reviewed

    S Aoki, G Boyd, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS   73   189 - 191   1999.3

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    We report the final results of the CP-PACS calculation for the quenched light hadron spectrum with the Wilson quark action. Our data support the presence of quenched chiral singularities, and this motivates us to use mass formulae based on quenched chiral perturbation theory in order to extrapolate hadron masses to the physical point. Hadron masses and decay constants in the continuum limit show unambiguous systematic deviations from experiment. We also report the results for light quark masses.

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  • Nonperturbative determination of anisotropy coefficients in lattice gauge theories Reviewed

    S. Ejiri, Y. Iwasaki, K. Kanaya

    Physical Review D - Particles, Fields, Gravitation and Cosmology   58 ( 9 )   94505   1998.10

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    We propose a new nonperturbative method to compute the derivatives of gauge coupling constants with respect to anisotropic lattice spacings (anisotropy coefficients), which are required in an evaluation of thermodynamic quantities from numerical simulations on the lattice. Our method is based on a precise measurement of the finite temperature deconfining transition curve in the lattice coupling parameter space extended to anisotropic lattices by applying the spectral density method. We test the method for the cases of SU(2) and SU(3) gauge theories at the deconfining transition point on lattices with the lattice size in the time direction (Formula presented) In both cases, there is a clear discrepancy between our results and perturbative values. A long standing problem, when one uses the perturbative anisotropy coefficients, is a nonvanishing pressure gap at the deconfining transition point in the SU(3) gauge theory. Using our nonperturbative anisotropy coefficients, we find that this problem is completely resolved: we obtain (Formula presented) and (Formula presented) on (Formula presented) and 6 lattices, respectively. © 1998 The American Physical Society.

    DOI: 10.1103/PhysRevD.58.094505

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  • Monopole condensation and quark confinement at finite temperature QCD Reviewed

    S Ejiri

    NUCLEAR PHYSICS A   629 ( 1-2 )   89C - 92C   1998.2

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    We study the relation between the abelian monopole condensation and the deconfinement phase transition of the finite-temperature pure QCD, and find that the expectation value of the Polyakov loop becomes zero when a long monopole loop is distributed uniformly in the configuration of the confinement phase as suggested in the previous Monte-Carlo simulations, whereas this value becomes non-zero when the long monopole loop disappears in the deconfinement phase. We also discuss the relation between the monopole picture and the spontaneous breaking of Z(N) symmetry that is the usual interpretation of the deconfinement transition in the finite-temperature SU(N) gauge theory.

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  • Critical exponents and Abelian dominance in SU(2) QCD Reviewed

    S Ejiri, S Kitahara, T Suzuki, K Yasuta

    PHYSICS LETTERS B   400 ( 1-2 )   163 - 168   1997.5

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    The critical properties of the abelian Polyakov loop and the Polyakov loop in terms of Dirac string are studied in finite temperature abelian projected SU(2) QCD. We evaluate the critical point and the critical exponents from each Polyakov loop in the maximally abelian gauge using the finite-size scaling analysis. Abelian dominance in this case is proved quantitatively. The critical point of each abelian Polyakov loop is equal to that of the non-abelian Polyakov loop within the statistical errors. Also, the critical exponents are in good agreement with those from non-abelian Polyakov loops. (C) 1997 Published by Elsevier Science B.V.

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  • Monopole action and monopole condensation in SU(3) lattice QCD Reviewed

    N Arasaki, S Ejiri, S Kitahara, Y Matsubara, T Suzuki

    PHYSICS LETTERS B   395 ( 3-4 )   275 - 282   1997.3

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    Effective monopole actions for various extended monopoles are derived from vacuum configurations after abelian projection in the maximally abelian gauge in T = 0 and T not equal 0 SU(3) lattice QCD. The actions obtained appear to be independent of the lattice volume adopted. At zero temperature, monopole condensation is seen to occur from energy-entropy balance in the strong coupling region. Larger beta is included in the monopole condensed phase as more extended monopoles are considered. The scaling seen in the SU(2) case is not yet observed. The renormalization flow diagram suggests the existence of an infrared fixed point. A hysteresis behavior is seen around the critical temperature in the case of the T not equal 0 action. (C) 1997 Elsevier Science B.V.

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  • Monopole condensation and Polyakov loop in finite-temperature pure QCD Reviewed

    S Ejiri

    NUCLEAR PHYSICS B   53   491 - 493   1997.2

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    We study the relation between the abelian monopole condensation and the deconfinement phase transition of the finite-temperature pure QCD. The expectation value of the monopole contribution to the Polyakov loop becomes zero when a long monopole loop is distributed uniformly in the configuration of the confinement phase. On the other hand, it becomes non-zero when the long monopole loop disappears in the deconfinement phase. We also discuss the relation between the monopole behaviors and the usual interpretation of the spontaneous breaking of Z(N) symmetry in finite-temperature SU(N) QCD. It is found that the boundary condition of the space direction is important to understand tile Z(N) symmetry in terms of the monopoles.

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  • Three topics of monopole dynamics in abelian projected QCD Reviewed

    T Suzuki, Y Matsubara, S Kitahara, S Ejiri, N Nakamura, F Shoji, M Sei, S Kato, N Arasaki

    NUCLEAR PHYSICS B   53   531 - 534   1997.2

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    Three topics about monopole dynamics after abelian projection are reported. The first is the new and detailed analyses of SU(2) monopole action obtained after the block-spin transformation on the dual lattice. The b = na(beta) dependence for all couplings are well fitted with a universal curve. The distance dependence of the couplings is well reproduced by a massive propagator with the mass m = 0.8 in unit of b. The second is the SU(3) monopole action recently obtained. The third is new interesting gauges showing abelian and monopole dominances as in the maximally abelian gauge.

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  • Disorder parameter of confinement Reviewed

    N Nakamura, Bornyakov, V, S Ejiri, S Kitahara, Y Matsubara, T Suzuki

    NUCLEAR PHYSICS B   53   512 - 514   1997.2

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    The disorder parameter of confinement-deconfinement phase transition based on the monopole action determined previously in SU(2) QCD are investigated. We construct an operator which corresponds to the order parameter defined in the abelian Higgs model. The operator shows proper behaviors as the disorder parameter in the numerical simulations of finite temperature QCD.

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  • Critical exponents in abelian projected SU(2) QCD Reviewed

    S Kitahara, S Ejiri, T Suzuki, K Yasuta

    NUCLEAR PHYSICS B   53   506 - 508   1997.2

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    The critical properties of the abelian Polyakov loop and the Polyakov loop in terms of Dirac string are studied in finite temperature abelian projected SU(2) QCD. The critical point and the critical exponents are determined from each Polyakov loop in the maximally abelian gauge using the finite-size scaling analyses. Those critical points and exponents are in good agreement with those from non-abelian Polyakov loops.

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  • Monopoles and spatial string tension in the high temperature phase of SU(2) QCD Reviewed

    S Ejiri

    PHYSICS LETTERS B   376 ( 1-3 )   163 - 168   1996.5

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    We studied a behavior of monopole currents in the high temperature (deconfinement) phase of abelian projected finite temperature SU(2) QCD in maximally abelian gauge. Wrapped monopole currents closed by periodic boundary play an important role for the spatial string tension that is a non-perturbative quantity in the deconfinement phase. The wrapped monopole current density seems to be non-vanishing in the continuum limit. These results may be related to Polyakov's analysis of the confinement mechanism using monopole gas in 3-dimensional SU(2) gauge theory with Higgs fields.

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  • Study of gauge (in)dependence of monopole dynamics Reviewed

    S Ejiri, S Kitahara, Y Matsubara, T Okude, T Suzuki, K Yasuta

    NUCLEAR PHYSICS B   47   322 - 325   1996.3

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    We investigated the gauge (in)dependence of the confinement mechanism due to monopole condensation in SU(2) lattice QCD by various abelian projections. We found (1) the string tension can be reproduced by monopoles alone also in Polyakov gauge and (2) the behaviors of the Polyakov loop at the critical temperature seem to be explained by the uniformity breaking of the monopole currents in every gauge.

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  • Monopoles in high temperature phase of SU(2) QCD Reviewed

    S Ejiri

    NUCLEAR PHYSICS B   47   539 - 542   1996.3

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    We investigated a behavior of monopole currents in the high temperature phase of abelian projected finite temperature SU(2) QCD in maximally abelian gauge. Wrapped monopole currents which are closed by periodic boundary play an important role for the spatial string tension. And the wrapped monopole current density seems to be non-vanishing in the continuum limit. These results may be related to Polyakov's analysis of the confinement mechanism using monopole gas in 3-dimensional SU(2) gauge theory with Higgs fields.

    DOI: 10.1016/0920-5632(96)00117-X

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  • Block spin transformation on the dual lattice and monopole action Reviewed

    T Suzuki, Y Matsubara, S Ejiri, K Yamada, N Arasaki

    NUCLEAR PHYSICS B   47   270 - 273   1996.3

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    To find a perfect lattice action in terms of monopole action on the dual lattice, we performed simulations of a monopole effective action obtained numerically from vacuum configurations in SU(2) QCD. Although the Polyakov loop behavior near T-c is well reproduced by the action, a small but repulsive term is needed in addition to get the string tension correctly. It is reported also a monopole effective action in SU(3) QCD which is expressed by one kind of monopole currents.

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  • STRING TENSION AND MONOPOLES IN T-NOT-EQUAL-O SU(2) QCD Reviewed

    S EJIRI, SI KITAHARA, Y MATSUBARA, T SUZUKI

    NUCLEAR PHYSICS B   42   481 - 483   1995.4

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    Monopole and photon contributions to abelian Wilson loops are calculated using Monte-Carlo simulations of finite-temperature SU(2) QCD in the maximally abelian gauge. The string tension is reproduced by monopole contribution alone also in finite temperature SU(2) QCD. The spatial string tension scales as root sigma proportional to g(2)(T)T and is reproduced almost by monopole contribution alone. Each configuration has one long monopole loop, and the long monopole loops alone are responsible for the string tension in the confinement phase. On the other hand, the spatial string tension in the deconfinement phase is reproduced by wrapped monopole loops alone.

    DOI: 10.1016/0920-5632(95)00286-I

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  • STRING TENSION AND MONOPOLES IN T-NOT-EQUAL-0 SU(2) QCD Reviewed

    S EJIRI, S KITAHARA, Y MATSUBARA, T SUZUKI

    PHYSICS LETTERS B   343 ( 1-4 )   304 - 309   1995.1

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    Monopole and photon contributions to abelian Wilson loops are calculated using Monte-Carlo simulations of finite-temperature SU(2) QCD in the maximally abelian gauge. Long monopole loops alone are responsible for the behavior of the string tension in the confinement phase. Short monopole loops and photons do not contribute to the string tension. The abelian and the monopole spatial string tensions (both of which agree with the full ones for beta &lt; beta(c)) show a g(4)(T)T-2 scaling behavior in the deconfinement phase. The abelian spatial string tension is in agreement with the full one even in the deconfinement phase.

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  • THE (DUAL) MEISSNER EFFECT IN SU(2) AND SU(3) QCD Reviewed

    Y MATSUBARA, S EJIRI, T SUZUKI

    NUCLEAR PHYSICS B   34   176 - 178   1994.4

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    After making an abelian projection in the maximally abelian gauge, we measure the distribution of abelian electric flux and monopole currents around an abelian Wilson loop iii SU (2) and SU (3) QCD. The (dual) Meissner effect is observed clearly. The vacua in the confinement phases of SU(2) and SU(3) are both at around the border between type-1 and type-2 (dual) superconductor.

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MISC

  • Gradient flowによる(2+1)‐flavor QCD状態方程式―物理点での試験研究―

    金谷和至, 石見涼, 梅田貴士, 江尻信司, 北沢正清, 鈴木博, 谷口裕介

    日本物理学会講演概要集(CD-ROM)   73 ( 1 )   ROMBUNNO.24pK201‐7   2018.3

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  • Equation of state in (2+1)-flavor QCD from the gradient flow - first test at the physical point

    Kanaya,Kazayuki, Iwami,Ryo, Umeda,Takashi, Ejiri,Shinji, Kitazawa,Masakiyo, Suzuki,Hiroshi, Taniguchi,Yusuke, WHOT-QCD,Collaboration

    Meeting Abstracts of the Physical Society of Japan   73   48 - 48   2018

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    DOI: 10.11316/jpsgaiyo.73.1.0_48

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  • Gradient flowを用いてみる一次相転移点近傍の熱力学量の性質

    白銀瑞樹, 江尻信司, 石見涼, 金谷和至, 北沢正清, 谷口裕介, 鈴木博, 梅田貴士, 若林直輝

    日本物理学会講演概要集(CD-ROM)   72 ( 2 )   ROMBUNNO.12aS31‐5   2017.9

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  • Lattice spacing dependence of critical mass in the heavy quark region of QCD

    Itagaki,Shota, Iwami,Ryo, Umeda,Takashi, Ejiri,Shinji, Kanaya,Kazuyuki, Kitazawa,Masakiyo, Taniguchi,Yusuke

    Meeting Abstracts of the Physical Society of Japan   72 ( 0 )   1 - 1   2017

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  • Properties of thermodynamic quantities near the first phase transition point observed using gradient flow method

    Shirogane,Mizuki, Ejiri,Shinji, Iwami,Ryo, Kanaya,Kazuyuki, Kitazawa,Masakiyo, Suzuki,Hiroshi, Taniguchi,Yusuke, Umeda,Takashi, Wakabayahi,Naoki

    Meeting Abstracts of the Physical Society of Japan   72 ( 0 )   2 - 2   2017

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  • 21pAX-7 Critical line in finite temperature and density QCD by O(4) scaling analysis

    Iwami,Ryo, Ejiri,S, Kanaya,K, Ohno,H, Umeda,T, Yoshida,S

    日本物理学会講演概要集   71 ( 1 )   55 - 55   2016.3

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  • Quenched QCDの一次相転移点における潜熱と圧力差

    白銀, 瑞樹, 江尻, 信司, 金谷, 和至, 北沢, 正清, 石見, 涼

    日本物理学会講演概要集   71 ( 1 )   53 - 53   2016.3

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  • 24pDK-11 Quark mass and chemical potential dependence of finite temperature phase transition in many flavor QCD

    Iwami Ryo, Ejiri Shinji, Yamada Norikazu

    Meeting Abstracts of the Physical Society of Japan   70   50 - 50   2015

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  • 19aSE-1 Quark mass and chemical potential dependence of finite temperature phase transition in many flavor QCD

    Iwami Ryo, Ejiri Shinji, Yamada Norikazu

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   9 - 9   2014.8

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  • 20aSE-7 Study of complex thermodynamical potential around the QCD critical point at finite density

    Ejiri Shinji, Shinno Yasuhiko, Yoneyama Hiroshi

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   12 - 12   2014.8

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  • 28pTG-5 Equation of state by a Lattice QGD calculation with the reweighting method

    Iwarni Ryo, Ejiri Shinji, Nakagawa Yoshiyuki

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   15 - 15   2014.3

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  • Technical problems in finite density lattice QCD and the attempts to solve them

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   5 - 5   2013.8

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  • Beta function by a Lattice QCD calculation with the reweighting method

    Iwami Ryo, Ejiri Shinji, Nakagawa Yoshiyuki

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   5 - 5   2013.8

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  • 27aRE-2 Study of phase structure in finite temperature many-flavor QCD

    Ejiri Shinji, Yamada Norikazu

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   8 - 8   2013.3

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  • ヒストグラム法を用いた有限密度格子QCD(基研研究会「熱場の量子論とその応用」,研究会報告) Reviewed

    中川, 義之, 青木, 慎也, 江尻, 信司, 初田, 哲男, 金谷, 和至, 前沢, 祐, 大野, 浩, 斎藤, 華, 梅田, 貴史

    Soryushiron Kenkyu   119 ( 4 )   F111 - F113   2012.2

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    DOI: 10.24532/soken.119.4C_F111

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  • 17aSC-1 Study of the critical line in the low density region of 2-flavor finite temperature and density lattice QCD

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   66 ( 2 )   7 - 7   2011.8

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  • 重いクォークに対する非閉じ込め相転移の次数(相構造,学生プレゼンテーション,熱場の量子論とその応用,研究会報告) Reviewed

    斎藤, 華, 江尻, 信司, 青木, 慎也, 金谷, 和至, 初田, 哲男, 前沢, 祐, 大野, 浩史, 梅田, 貴史

    Soryushiron Kenkyu   118 ( 4 )   0 - 0   2011.2

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  • 有限密度QCDの臨界点近傍の特異性(相図,熱場の量子論とその応用,研究会報告)

    江尻 信司, 米山 博志

    素粒子論研究   118 ( 4 )   D125 - D126   2011

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    DOI: 10.24532/soken.118.4_D125

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  • 13aSC-5 Scaling behavior of 2-flavor QCD at finite density

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   65 ( 2 )   7 - 7   2010.8

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  • 29pXF-5 Study of the phase structure of hot and dense lattice QCD

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   64 ( 1 )   15 - 15   2009.3

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  • 22aSB-7 Hot and Dense QCD from Lattice Simulations

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   63 ( 2 )   64 - 64   2008.8

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  • 高温高密度での格子量子色力学

    江尻信司

    原子核研究   51 ( Suppl. 1 )   17 - 24   2007.3

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  • 22aSC-1 Heavy quark potential in full QCD lattice simulations at finite temperature

    Maezawa,Y, Aoki,S, Ejiri,E, Hatsuda,T, Ishii,N, Kanaya,K, Taniguchi,Y, Ukita,N

    Meeting abstracts of the Physical Society of Japan   61 ( 2 )   17   2006.8

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  • 30aWB-7 QCD phase transition at finite density and temperature

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   61 ( 1 )   46 - 46   2006.3

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  • Study of QCD phase transition by lattice simulations(Hadrons at finite density)

    Ejiri Shinji

    Soryushiron Kenkyu Electronics   114 ( 2 )   B45 - B47   2006

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    We will review the recent studies of the QCD phase structure by numerical simulations in the low density region. It is important to investigate the phase structure and the equation of state of QCD in the low density regime which is interesting for heavy-ion collision experiments. The studies of the phase structure and the equation of state can provide basic input for the analysis of the experimental signatures for QGP formation. In the last several years, remarkable progress in exploring the QCD phase structure in the temperature (T) and quark chemical potential (μ_q) plane have been made in numerical studies of lattice QCD. The phase transition line, separating hadron phase and quark-gluon plasma phase, was investigated from μq=0 to finite μ_q [1, 2, 3, 4, 5], and the equation of state was also analyzed quantitatively at low density [3, 6]. Moreover the study of the endpoint of first order phase transition line in the (T, μ_q) plane, whose existence is suggested by phenomenological studies [7, 8], is particularly interesting both from the experimental and theoretical points of view. To find this endpoint, event by event fluctuations have been measured in heavy ion collisions. In this report, we review recent progress of lattice QCD simulations, highlighting the study of the critical endpoint in the (T,μ_q) plane. The lattice QCD at nonzero baryon density is known to have a serious problem called "sign problem", however this problem is not very serious for the studies in the low density region, and interesting results have been gradually obtained using the following approaches.

    DOI: 10.24532/soken.114.2_B45

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  • 格子QCDの数値シミュレーションによる高温高密度でのQCD相転移の研究

    江尻信司

    素粒子論研究   112 ( 3 )   C85 - C94   2005.12

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    DOI: 10.24532/soken.112.3_C85

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  • 28aSJ-2 Study of QCD at high temperature and density by numerical simulations

    Ejiri Shinji

    Meeting abstracts of the Physical Society of Japan   59 ( 2 )   31 - 31   2004.8

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  • Hybrid quarkonia with dynamical sea quarks

    T Manke, AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   64 ( 9 )   097505/1-097505/4   2001.11

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    We present a dynamical lattice calculation with two flavors for bottomonium states with an additional gluonic excitation. Using improved actions for the quarks and gauge fields at a lattice spacing of a approximate to0.1 fm, we find 10,977(61)(62) GeV for the energy of the lowest lying b (b) over barg hybrid, where the first error is statistical and the second denotes the systematic uncertainty due to the determination of scale. In a parallel quenched simulation we demonstrate explicitly that vacuum polarization effects are less than 10% of the splitting with the ground state.

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  • 22pSC-9 Thermodynamics of SU(3) gauge theory on anisotropic lattices

    Namekawa,Y, Aoki,S, Burkhalter,R, Ejiri,S, Fukugita,M, Hashimoto,S, Ishizuka,N, Iwasaki,Y, Kanaya,K, Kaneko,T, Kuramashi,Y, Lesk,V, Okamoto,M, Okawa,M, Taniguchi,Y, Ukawa,A, Yoshie,T

    Meeting abstracts of the Physical Society of Japan   56 ( 2 )   3 - 3   2001.9

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  • 有限温度・有限密度QCDの最近の発展

    江尻信司

    素粒子論研究   103 ( 1 )   A41 - A53   2001.4

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    この報告では、有限温度・有限密度格子QCDの数値シミュレーションによる研究の最近の発展についてレビューする。特に、フレーバー数2と3のQCDの相転移温度の研究、カイラル相転移の臨界現象の性質、クォーク・グルーオン・プラズマの状態方程式といった話題について議論する。

    DOI: 10.24532/soken.103.1_A41

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  • Sea quark effects on quarkonia

    T Manke, AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, K Nagai, M Okawa, HP Shanahan, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   62 ( 11 )   114508/1-114508/13   2000.12

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    We study the effects of two dynamical sea quarks on the spectrum of heavy quarkonia. Within the non-relativistic approach to lattice QCD we find sizable changes to the hyperfine splitting, but we do not observe any changes for the fine structure. We also investigate the scaling behavior of our results for several different lattice spacings.

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  • A Study on the Existance of Yang-Mills Theoroes with Latrge Extra Dimension

    Ejiri S., Kubo J., Murata M.

    Meeting abstracts of the Physical Society of Japan   55 ( 2 )   6 - 6   2000.9

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  • Equation of state for pure SU(3) gauge theory with renormalization group improved action

    M Okamoto, AA Khan, S Aoki, R Burkhalter, S Ejiri, M Fukugita, S Hashimoto, N Ishizuka, Y Iwasaki, K Kanaya, T Kaneko, Y Kuramashi, T Manke, K Nagai, M Okawa, A Ukawa, T Yoshie

    PHYSICAL REVIEW D   60 ( 9 )   094510/1-094510/8   1999.11

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    A lattice study of the equation of state for pure SU(3) gauge theory using a renormalization-group (RG) improved action is presented. The energy density and pressure are calculated on a 16(3) X 4 and a 32(3) X 8 lattice employing the integral method. Extrapolating the results to the continuum limit, we find the energy density and pressure to be in good agreement with those obtained with the standard plaquette action within the error of 3-4%. [S0556-2821(99)07819-4].

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  • 29p-YP-4 The monopole action using the improved action

    Suzuki Tsuneo, Ejiri Shinji, Shouji Fumiyosi, Yamagisi Kentarou

    Meeting abstracts of the Physical Society of Japan   52 ( 1 )   7 - 7   1997.3

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  • 有限温度Lattice QCDにおけるMonopole(量子場の理論の新しい展開,研究会報告)

    江尻 信司

    素粒子論研究   92 ( 3 )   C71 - C75   1995.12

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    我々、金沢のグループでは、QCDにおけるクォークの閉じ込め機構が、monopoleの凝縮による、Dnal Meissner効果として理解できるかどうかを、Lattice QCDのMonte-Carlo simulationによって確かめるといった研究をつづけています。ここでは、SU(2)pnre QCDの有限温度閉じ込め・非閉じ込め相転移における、monopoleの役割について、我々が得た結果を報告します。

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  • String tension and monopole on finite temperature Lattice QCD((5).Development in Lattice and Field theroy,YITP workshop(Particle physics and its future perspective))

    Ejiri S.

    Soryushiron Kenkyu   92 ( 1 )   A66   1995.10

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  • 30a-SH-7 Gauge Independence of Monopole Dynamics

    Ejiri S., Matsubara Y., Suzuki T.

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   1995 ( 1 )   20 - 20   1995.9

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  • 30a-SH-10 Monopole Action in Lattice QCD

    Arasaki Natsuko, Ejiri Shinji, Matsubara Yoshimi, Suzuki Tsuneo

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   1995 ( 1 )   21 - 21   1995.9

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  • Monopole Action in Lattice QCD

    Arasaki Natsuko, Ejiri Shinji, Matsubara Yoshimi, Suzuki Tsuneo

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   50 ( 1 )   15 - 15   1995.3

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  • Spatial string tension and monopoles in finite temperature Latice QCD

    Ejiri Shinji

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   50 ( 1 )   17 - 17   1995.3

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  • MONOPOLE ACTION AND THE RENORMALIZED TRAJECTORY IN SU(2)QCD

    Ejiri Shinji, Matsubara Yoshimi, Suzuki Tsuneo, Yotsuji Kenji

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   50 ( 1 )   16 - 16   1995.3

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  • 28p-S-1 Monopole behaviors in abelian projected lattice QCD

    Itho M, Ilyar S, Ejiri S, Shiba H, Suzuki T

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   49 ( 1 )   6 - 6   1994.3

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Presentations

  • 重クォーク領域における有限密度格子QCDの臨界点決定のためのホッピングパラメータ展開

    江尻信司, 金谷和至, 北沢正清, 若林直輝

    基研研究会「熱場の量子論とその応用」  2022.9 

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  • Convergence of hopping parameter expansions for determining critical points in the heavy quark region

    S. Ejiri, K. Kanay, M. Kitazawa, N. Wakabayashi

    The Physical Society of Japan 2022 Annual (77th) Meeting  2022.3 

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  • Phase structure of QCD in the heavy quark region Invited International conference

    Shinji Ejiri

    YITP workshop “QCD phase diagram and lattice QCD”  2021.10  Yukawa institute, Kyoto University

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    Event date: 2021.10

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

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  • Particle density probability distribution function and center symmetry breaking in finite density lattice gauge theories International conference

    Shinji Ejiri

    Lattice 2021, International Symposium on Lattice Field Theory  2021.7 

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    Event date: 2021.7

    Language:English   Presentation type:Oral presentation (general)  

    Venue:Massachusetts, MIT (online)   Country:United States  

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  • Latent heat and pressure gap at the first-order phase transition point of SU(3) gauge theory using the small flow-time expansion method

    Shinji Ejiri, Mizuki Shirogane, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Hiroshi Suzuki, Yusuke Taniguchi, Takashi Umeda

    The Physical Society of Japan 2021 Annual (76th) Meeting  2021.3 

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    Event date: 2021.3

    Presentation type:Oral presentation (general)  

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  • Avoiding the sign problem in finite density lattice gauge theories by the center symmetry

    Shinji Ejiri

    2020.9 

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    Event date: 2020.9

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Particle density probability distribution function using an avoidance method of the sign problem by center symmetry in finite density lattice gauge theories

    Shinji Ejiri

    2020.8 

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    Event date: 2020.8

    Language:Japanese   Presentation type:Poster presentation  

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  • End point of first order phase transitions and sign problem in finite density lattice gauge theories Invited

    Shinji Ejiri

    2020.5 

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    Event date: 2020.5

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

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  • Quark number distribution function and center symmetry in finite density lattice QCD

    Shinji Ejiri

    International Symposium on Clustering as a Window on the Hierarchical Structure of Quantum Systems (CLUSHIQ2020)  2020.1 

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    Event date: 2020.1

    Language:English   Presentation type:Poster presentation  

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  • 有限密度格子QCDにおけるクォーク密度確率分布関数と符号問題について

    江尻 信司

    日本物理学会2019年秋季大会  2019.9 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:山形大学、山形市  

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  • 有限密度格子ゲージ理論における符号問題とセンター対称性

    EJIRI Shinji

    2019.9 

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  • Center symmetry and the sign problem of finite density lattice gauge theory International conference

    EJIRI Shinji

    XQCD 2019, International workshop on QCD in extreme conditions  2019.6 

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    Language:English   Presentation type:Poster presentation  

    Venue:Univ. of Tsukuba, Tokyo, Japan  

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  • Determination of the endpoint of the first order deconfiniement phase transition in the heavy quark region of QCD International conference

    EJIRI Shinji

    Lattice 2019, International Symposium on Lattice Field Theory  2019.6 

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    Venue:Wuhan, China  

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  • Numerical study of the endpoint of first order phase transition lines in finite density Lattice QCD Density Fluctuations, Sign problem Invited

    EJIRI Shinji

    2019.5 

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  • Canonical partition function of lattice QCD and finite density phase transitions Invited

    Shinji Ejiri

    Shikoku Seminar 2018 (Sign problem and its application)  2018.12 

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  • Thermodynamics near the first order phase transition point of SU(3) gauge theory International conference

    Shinji Ejiri

    Long-term Workshop on New Frontiers in QCD 2018 (NFQCD2018)  2018.5 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:Kyoto University, Kyoto, Japan  

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  • Finite Density Lattice QCD Invited International conference

    Shinji Ejiri

    Reimei Workshop "Hadronic Resonances and Dense Nuclear Matter"  2017.12 

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    Venue:Ibaraki Quantum Beam Research Center, Tokai, Ibaraki, Japan  

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  • 格子ゲージ理論による有限密度QCDの臨界点探索 Invited

    江尻信司

    研究会「J-PARCエネルギー領域重イオン衝突のダイナミクス」  2017.9 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:高エネルギー加速器研究機構、東海キャンパス、茨城県東海村  

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  • Determination of latent heat at the finite temperature phase transition of SU(3) gauge theory International conference

    Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Yusuke Taniguchi, Hiroshi Suzuki, Mizuki Shirogane, Takashi Umeda, Naoki Wakabayashi

    Lattice 2017, International Symposium on Lattice Field Theory  2017.6 

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    Language:English   Presentation type:Poster presentation  

    Venue:Granada, Spain  

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  • Determination of latent heat at the finite temperature phase transition of SU(3) gauge theory International conference

    Shinji Ejiri, Ryo Iwami, Kazuyuki Kanaya, Masakiyo Kitazawa, Yusuke Taniguchi, Hiroshi Suzuki, Mizuki Shirogane, Takashi Umeda, Naoki Wakabayashi

    Lattice 2016, International Symposium on Lattice Field Theory  2016.7 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:University of Southampton, Southampton, UK  

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  • Phase structure of QCD at high temperature and high density by numerical simulations of lattice QCD Invited International conference

    Shinji Ejiri

    NIC-XIV School (School for Nuclei in the Cosmos XIV)  2016.6 

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    Language:English   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

    Venue:新潟大学  

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  • Critical point search from an extended parameter space of lattice QCD at finite temperature and density International conference

    Shinji Ejiri, Ryo Iwami, Norikazu Yamada, Hiroshi Yoneyama

    Quark Matter 2015, International Conference on Ultra Relativistic Nucleus Nucleus Collisions  2015.9 

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    Venue:神戸市  

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  • Phase structure in an extended parameter space of lattice QCD at finite temperature and density Invited International conference

    Shinji Ejiri

    International workshop on QCD in extreme conditions  2015.9 

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    Venue:華中師範大学, 武漢, 中国  

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  • 再重みづけ法による高温高密度格子QCD Invited

    江尻信司

    有限温度密度系の物理と格子QCDシミュレーション  2015.9 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:筑波大学計算科学研究センター, つくば市  

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  • Quark mass dependence of the nature of QCD phase transition Invited International conference

    Shinji Ejiri

    CCS-BNL Workshop on Lattice Gauge Theories 2015 (CCS-BNL LGT 2015)  2015.3  Center for Computational Sciences, University of Tsukuba

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    Venue:Tsukuba, Japan  

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  • First order transitions in finite temperature and density QCD with two and many flavors Invited International conference

    Shinji Ejiri

    Hadrons and Hadron Interactions in QCD 2015 (HHIQCD2015)  2015.2  京都大学 基礎物理学研究所

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    Venue:京都  

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  • First order transition regions in the quark masses and chemical potential parameter space of many-flavor QCD International conference

    Shinji Ejiri

    Critical Point and Onset of Deconfinement (CPOD 2014)  2014.11 

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    Venue:Bielefeld University, Bielefeld, Germany  

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  • 有限温度系 Invited

    江尻信司

    KEK格子ゲージ理論スクール  2014.11  高エネルギー加速器研究機構

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    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

    Venue:つくば市  

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  • Quark mass dependence of the nature of QCD phase transition at high temperature and density by a histogram method Invited International conference

    Shinji Ejiri

    Quark Confinement and the Hadron Spectrum XI (Confinement XI)  2014.9 

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    Venue:St. Petersburg, Russia  

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  • 多フレーバー格子ゲージ理論からの高温高密度QCD相転移の研究

    江尻信司

    熱場の量子論とその応用  2014.9  理化学研究所 iTHES

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:埼玉県和光市  

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  • 高温高密度格子QCDの最近の進展 Invited

    江尻信司

    素粒子物理学の進展2014  2014.7 

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    Venue:京都大学基礎物理学研究所  

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  • Quark mass dependence of finite temperature phase transitions in QCD with many flavors of Wilson fermions International conference

    Shinji Ejiri, Norikazu Yamada

    "Lattice 2014", International Symposium on Lattice Field Theory  2014.6 

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    Language:English   Presentation type:Poster presentation  

    Venue:Columbia University, New York, USA  

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  • Nature of phase transitions in finite temperature and density QCD with many-flavors Invited International conference

    Shinji Ejiri

    SIGN 2014, International EMMI Workshop on the Sign Problem in QCD and beyond  2014.2  GSI, EMMI

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    Venue:Darmstadt, Germany  

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  • Numerical simulations to understand QCD phase transition at high temperature and density Invited International conference

    Shinji Ejiri

    Workshop on Lattice QCD at finite temperature and density  2014.1  高エネルギー加速器研究機構

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    Language:English   Presentation type:Oral presentation (keynote)  

    Venue:筑波  

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  • 有限温度・有限密度格子QCD研究の現状と今後の展望 Invited

    江尻信司

    新学術領域「素核宇宙融合による計算科学に基づいた重層的物質構造の解明」のまとめと今後を語る研究会  2013.12 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:宮城県鳴子温泉  

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  • Nature of QCD phase transition at finite temperature and density Invited International conference

    Shinji Ejiri

    Long-term Workshop on New Frontiers in QCD 2013 (NFQCD2013)  2013.11  京都大学基礎物理学研究所

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    Venue:京都  

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  • QCD phase structure by a histogram method Invited International conference

    Shinji Ejiri

    Lattice Field Theory on multi-PFLOPS computers, German-Japanese Seminar 2013  2013.11 

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    Venue:Regensburg, Germany  

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  • 有限密度格子QCDの数値的研究における技術的な困難とその解決にむけた試み Invited

    江尻信司

    日本物理学会2013年秋季大会  2013.9  日本物理学会

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:高知大学  

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  • 高温高密度多フレーバーQCDにおける一次相転移の終点

    江尻信司, 山田憲和

    熱場の量子論とその応用  2013.8 

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    Language:Japanese   Presentation type:Poster presentation  

    Venue:京都大学基礎物理学研究所  

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  • Nature of finite temperature and density phase transitions in many-flavor QCD International conference

    Shinji Ejiri, Norikazu Yamada

    "Lattice 2013" International Symposium on Lattice Field Theory  2013.7 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:Mainz, Germany  

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  • QCDの有限温度相転移、複合ヒッグス模型、電弱相転移

    江尻信司

    第41回北陸信越地区素粒子論グループ研究会  2013.5 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:富山県、国立立山青少年自然の家  

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  • 有限温度多フレーバーQCDの相構造の研究

    江尻信司, 山田憲和

    日本物理学会第68回年次大会  2013.3  日本物理学会

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:広島大学  

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  • Study of finite density lattice QCD by the histogram method International conference

    Shinji Ejiri

    Symposium on Quarks to Universe in Computational Science (QUCS 2012)  2012.12  新学術領域研究「素核宇宙融合による計算科学に基づいた重層的物質構造の解明」

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:奈良県新公会堂  

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  • Numerical study of QCD phase structure at finite temperature and density International conference

    Shinji Ejiri

    Conference on Computational Physics 2012 (CCP 2012)  2012.10  C20, IUPAP

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    Venue:Kobe, Japan  

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  • Critical point in finite density 2-flavor QCD by the histogram method International conference

    Shinji Ejiri

    Workshop on "QCD Structure"  2012.10  Central China Normal University,

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    Venue:Wuhan, China  

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  • Phase structure of lattice QCD at finite density by a histogram method International conference

    Shinji Ejiri

    International Workshop on the Sign Problem in QCD and Beyond  2012.9  Regensburg University

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    Venue:Regensburg, Germany  

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  • Study of finite density lattice QCD by a histogram method International conference

    Shinji Ejiri

    New Frontiers in Lattice Gauge Theory  2012.8 

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    Venue:The Galileo Galilei Institute for Theoretical Physics, Florence, Italy  

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  • Probability distribution functions in the finite density lattice QCD International conference

    S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Nakagawa, H. Ohno, H. Saito, T. Umeda, HOT-QCD Collaboration

    "Lattice 2012", International Symposium on Lattice Field Theory  2012.6 

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    Venue:Cairns, Australia  

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  • 有限密度格子QCDにおける符号問題の解決に向けた状態密度法による試み

    江尻信司

    第2回HPCI戦略プログラム、分野2×分野5異分野交流研究会-量子モンテカルロ計算-  2012.5 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:東京大学、物性研究所  

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  • Phase structure of finite density lattice QCD by a histogram method International conference

    Shinji Ejiri

    YIPQS-HPCI international molecule-type workshop on New-type of Fermions on the Lattice  2012.2  Yukawa Institute for Theoretical Physics

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    Venue:Kyoto, Japan  

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  • Finite Density Lattice QCD

    江尻信司

    HPCI研究会「計算的手法による素粒子論研究の広がり」  2011.12 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:高エネルギー加速器研究機構  

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  • 高温高密度での格子QCDシミュレーション

    江尻信司

    素核融合による計算基礎物理学の進展  2011.12 

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:三重県志摩市  

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  • Finite Density Lattice QCD by a Histogram Method International conference

    Shinji Ejiri

    2nd Workshop on Quarks and Hadrons under Extreme Conditions - Lattice QCD, Holography, Topology, and Physics at RHIC / LHC  2011.11 

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    Venue:Keio University, Kanagawa, Japan  

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  • Numerical Study of QCD Phase Diagram at High Temperature and Density by a Histogram Method International conference

    Shinji Ejiri

    7th International Workshop on Critical Point and Onset of Deconfinement (CPOD 2011)  2011.11  Central China Normal University

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    Venue:Wuhan, China  

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  • Study of QCD Phase Transition at Finite Density by a Histogram Method International conference

    Shinji Ejiri

    Workshop on "Fluctuations, Correlations and RHIC Low Energy Runs"  2011.10  Brookhaven National Laboratory

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    Venue:Upton, New York, USA  

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  • 低密度領域における2フレーバー有限温度密度格子QCDの臨界線の研究

    江尻信司, HOT-QCD Collaboration

    日本物理学会2011年秋季大会  2011.9  日本物理学会

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:弘前大学  

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  • 有限温度密度格子QCD計算

    江尻信司

    格子QCD将来戦略検討会  2011.7 

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    Venue:東京大学理学部  

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  • Study of finite density lattice QCD by a density of state method International conference

    Shinji Ejiri, HOT-QCD Collaboration

    International workshop "Extreme QCD 2011"  2011.7 

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    Venue:San Carlos, Mexico  

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  • QCD thermodynamics by numerical simulations of Lattice QCD with Wilson-type quarks International conference

    S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, Y. Nakagawa, H. Ohno, H. Saito, T. Umeda, HOT-QCD Collaboration

    "Quark Matter 2011", International Conference on Ultra Relativistic Nucleus Nucleus Collisions  2011.5 

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    Language:English   Presentation type:Poster presentation  

    Venue:Annecy, France  

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  • Nature of QCD phase transition in the chemical potential and quark mass parameter space International conference

    Shinji Ejiri, HOT-QCD Collaboration

    International workshop "Nonperturbative Aspects of QCD at Finite Temperature and Density"  2010.11  Center for Computational Science, University of Tsukuba

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    Venue:Tsukuba, Ibaraki, Japan  

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  • Density of state method for the study of finite density lattice QCD International conference

    Shinji Ejiri, HOT-QCD Collaboration

    "Lattice QCD confronts experiments", Japanese German seminar 2010  2010.11 

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    Venue:Mishima, Shizuoka, Japan  

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  • 高温・高密度格子QCDの最近の進展

    江尻信司

    次世代格子ゲージシミュレーション研究会  2010.9 

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    Language:Japanese   Presentation type:Oral presentation (keynote)  

    Venue:埼玉県和光市、理化学研究所  

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  • 有限密度での2フレーバーQCDのスケーリング則

    江尻信司, HOT-QCD Collaboration

    日本物理学会2010年秋季大会  2010.9  日本物理学会

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    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:福岡県北九州市、九州工業大  

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  • Lattice QCD at finite density International conference

    Shinji Ejiri

    Summer Institute 2010 (Phenomenology part)  2010.8 

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    Venue:Fujiyoshida, Yamanashi, Japan  

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  • 格子QCDによる有限温度・密度解析

    江尻信司

    新学術領域研究「素核宇宙融合による計算科学に基づいた重層的物質構造の解明」計画研究A01班「量子色力学にもとづく真空構造とクォーク力学」第3回A01班研究会  2010.7 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:筑波大学計算科学研究センター  

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  • A method to study finite density lattice QCD International conference

    Shinji Ejiri

    WE-Heraeus Seminar "Extreme QCD 2010"  2010.6  Wilhelm und Else Heraeus Stiftung

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    Venue:Bad Honnef, Germany  

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  • Scaling behavior of chiral phase transition in two-flavor QCD with improved Wilson quarks at finite density International conference

    S. Ejiri, S. Aoki, T. Hatsuda, K. Kanaya, Y. Maezawa, Y. Nakagawa, H. Ohno, H. Saito, T. Umeda, HOT-QCD Collaboration

    "Lattice 2010", International Symposium on Lattice Field Theory  2010.6 

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    Language:English   Presentation type:Poster presentation  

    Venue:Villasimius, Sarginia, Italy  

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  • Lattice QCD at finite temperature and density International conference

    Shinji Ejiri

    YITP long-term workshop "New Frontiers in QCD 2010 (NFQCD10)"  2010.1  Yukawa Institute, Kyoto University

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    Venue:Kyoto, Japan  

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Awards

  • 2008 Nakamura Seitaro prize

    2009.3  

    Soryushi Shogakukai

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    Award type:Award from publisher, newspaper, foundation, etc.  Country:Japan

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Research Projects

  • 有限密度格子QCDにおける粒子密度確率分布関数と符号問題の回避法

    Grant number:21K03550  2021.4 - 2025.3

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    江尻 信司

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    Authorship:Principal investigator 

    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

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  • 有限密度格子QCDにおける一次相転移線の終点の数値的研究

    2019.4 - 2021.3

    日本学術振興会  科学研究費補助金事業、新学術領域研究、公募研究 

    江尻 信司

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\2990000 ( Direct Cost: \2300000 、 Indirect Cost:\690000 )

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  • 計算機シミュレーションによる超高温・高密度状態での強い相互作用の性質

    2018.7 - 2019.3

    民間財団等  内田エネルギー科学振興財団、助成事業 

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

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  • Phase structure of lattice field theories

    2016.4 - 2017.3

    Bilateral Programs, Joint research seminar with Germany(DFG)

    Shinji Ejiri

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\2000000 ( Direct Cost: \1400000 、 Indirect Cost:\600000 )

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  • 確率分布関数に着目した高温高密度格子QCDの臨界点の探索

    2014.4 - 2018.3

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    高温高密度でのQCDの相構造を探索するための、数値シミュレーションによる理論的研究を行う。

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  • 数値シミュレーションによる高温高密度QCDの相構造の研究

    2011.4 - 2014.3

    日本学術振興会  科学研究費助成事業  基盤研究(C)

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    数値シミュレーションによって高温高密度QCDの相構造を研究する。

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  • 状態密度法による有限密度QCDの計算方法の開発

    2011.4 - 2013.3

    日本学術振興会  科学研究費助成事業、新学術領域研究、公募研究  新学術領域研究

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    有限密度QCDの計算を行うために、状態密度法という計算方法の開発を行う。

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  • 高温高密度での格子量子色力学の数値的研究

    2010.8 - 2011.3

    日本学術振興会  科学研究費助成事業  研究活動スタート支援

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    高温高密度での格子量子色力学の数値的研究を行った。

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  • 数値シミュレーションによる高温高密度格子量子色力学の研究

    2006.4 - 2007.3

    日本学術振興会  科学研究費助成事業  若手研究(B)

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    コンピューターシミュレーションによって高温高密度格子量子色力学の研究を行った。

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  • 数値シミュレーションによる高温高密度状態での量子色力学の研究

    2005.11 - 2006.11

    民間財団等  住友財団基礎科学研究助成 

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    Grant type:Competitive

    数値シミュレーションによって高温高密度状態での量子色力学を研究した。

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  • コンピューター・シミュレーションによる有限温度QCDの研究

    1998.4 - 2001.3

    科学研究費助成事業  特別研究員推奨費

    江尻信司

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    Authorship:Principal investigator  Grant type:Competitive

    コンピューター・シミュレーションにより有限温度QCDの研究を行った。

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Teaching Experience (researchmap)

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Teaching Experience

  • 理学基礎演習

    2022
    Institution name:新潟大学

  • 素粒子物理学

    2021
    Institution name:新潟大学

  • 台湾スプリングセミナー II

    2021
    Institution name:新潟大学

  • 物理学基礎CI

    2021
    Institution name:新潟大学

  • 台湾スプリングセミナー I

    2021
    Institution name:新潟大学

  • 理学スタディ・スキルズ

    2021
    Institution name:新潟大学

  • 現代物理学セミナーA

    2020
    Institution name:新潟大学

  • 計算物理学B

    2020
    Institution name:新潟大学

  • 計算物理学A

    2020
    Institution name:新潟大学

  • 現代物理学セミナーB

    2020
    Institution name:新潟大学

  • 専門力アクティブ・ラーニング

    2018
    -
    2021
    Institution name:新潟大学

  • 台湾スプリングセミナー I

    2018
    Institution name:新潟大学

  • 台湾スプリングセミナー II

    2018
    Institution name:新潟大学

  • 計算物理学演習

    2017
    Institution name:新潟大学

  • 理学スタディ・スキルズ

    2017
    -
    2021
    Institution name:新潟大学

  • 物理学基礎C2

    2017
    -
    2020
    Institution name:新潟大学

  • 物理学基礎C1

    2017
    -
    2020
    Institution name:新潟大学

  • 物理学演習D

    2017
    Institution name:新潟大学

  • 物理学演習C

    2017
    Institution name:新潟大学

  • 素粒子物理学I

    2017
    Institution name:新潟大学

  • 現代物理学

    2016
    Institution name:新潟大学

  • 物理学基礎ゼミ

    2016
    Institution name:新潟大学

  • 課題研究a

    2016
    Institution name:新潟大学

  • 課題研究b

    2016
    Institution name:新潟大学

  • 物理学への招待B

    2015
    -
    2016
    Institution name:新潟大学

  • 課題探索特講

    2015
    Institution name:新潟大学

  • 理論素粒子物理学I

    2014
    Institution name:新潟大学

  • ゲージ場理論特論Ⅰ

    2014
    Institution name:新潟大学

  • 物理学基礎CⅠ

    2014
    -
    2016
    Institution name:新潟大学

  • 数理物質科学特定研究ⅡA(物理学)

    2014
    -
    2015
    Institution name:新潟大学

  • 数理物質科学特定研究ⅡB(物理学)

    2014
    -
    2015
    Institution name:新潟大学

  • 数理物質科学演習Ⅱ(物理学)

    2014
    -
    2015
    Institution name:新潟大学

  • 数理物質科学演習Ⅰ(物理学)

    2014
    -
    2015
    Institution name:新潟大学

  • 数理物質科学特定研究Ⅰ(物理学)

    2014
    -
    2015
    Institution name:新潟大学

  • 解析力学

    2013
    Institution name:新潟大学

  • 物理学演習

    2011
    -
    2016
    Institution name:新潟大学

  • 素粒子物理学II

    2010
    -
    2016
    Institution name:新潟大学

  • 基礎物理学演習II

    2010
    -
    2016
    Institution name:新潟大学

  • 基礎物理学演習I

    2010
    -
    2011
    Institution name:新潟大学

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