Publishing type：Research paper (scientific journal)  

We compute the density of a spin-$\frac32$ particle, the raritron, produced
at the end of inflation due to gravitational interactions. We consider a
background inflaton condensate as the source of this production, mediated by
the exchange of a graviton. This production greatly exceeds the gravitational
production from the emergent thermal bath during reheating. The relic abundance
limit sets an absolute minimum mass for a stable raritron, though there are
also model dependent constraints imposed by unitarity. We also examine the case
of gravitational production of a gravitino, taking into account the goldstino
evolution during reheating. We compare these results with conventional
gravitino production mechanisms.

DOI： 10.1103/PhysRevD.108.115027

arXiv

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Other Link： http://arxiv.org/pdf/2309.15146v1

The recently proposed formalism of extended Jordan-Brans-Dicke gravity makes
it possible to calculate energy loss rate due to both gravitational wave and
scalar field (giving the origin of dark energy) wave emission at merger of a
black hole and a neutron star; a binary system of no scalar hair and a star
with the scalar charge. The scalar field emission changes orbit parameters of
the binary system, thereby changes detectable gravitational wave emission. When
neutron stars carry significantly large scalar charge, significant dark wave
(namely, scalar field wave) emission occurs at the same time of gravitational
wave emission. It is found that solutions of coupled differential equations
predict non-vanishing remnant dark charge after the gravitational collapse.
This gives two interesting possibilities: (1) the no-hair conjecture of black
hole is violated, or (2) a bosonic cloud is formed outside the event horizon of
black hole. The bosonic cloud proposed in the literature is a gigantic atom
made of gravitationally bound dark energy quanta surrounding a black hole. One
can either constrain, or even determine, parameters of extended
Jordan-Brans-Dicke gravity from accumulated gravitational wave observations of
merging black hole and neutron star.

arXiv

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Other Link： http://arxiv.org/pdf/2306.07592v1

A coherent field over the entire universe is an attractive picture in
studying the dark sector of the universe. The misalignment mechanism, which
relies on inflation to achieve homogeneousness of the field, is a popular
mechanism for producing such a coherent dark matter. Nevertheless, unlike a
scalar field case, a vector boson field suffers because its energy density is
exponentially suppressed by the scale factor during the cosmic expansion. We
show that if the vector field gets a mass from a scalar field, whose value
increases by orders of magnitude, the suppression can be compensated, and the
misalignment can produce the coherent vector boson that has a sizable amount of
energy density in the present universe. Quintessence can be such a scalar
field.

arXiv

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Other Link： http://arxiv.org/pdf/2306.01291v1

Since electroweak symmetry is generally broken during inflation, the Standard
Model Higgs field can become supermassive even after the end of inflation. In
this paper, we study the non-thermal phase space distribution of the Higgs
field during reheating, focusing in particular on two different contributions:
primordial condensate and stochastic fluctuations. We obtain their analytic
formulae, which agree with the previous numerical result. As a possible
consequence of the non-thermal Higgs spectrum, we discuss perturbative Higgs
decay during reheating for the case it is kinematically allowed. We find that
the soft-relativistic and hard spectra are dominant in the decay rate of the
stochastic fluctuation and that the primordial condensate and stochastic
fluctuations decay almost at the same time.

arXiv

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Other Link： http://arxiv.org/pdf/2304.12578v1

Cosmological analysis of extended Jordan-Brans-Dicke (eJBD) gravity is
presented in the Einstein metric frame in which gravitational interaction is
readily understandable. Our formulation is the first systematic investigation
of how to introduce lagrangian of standard particle physics in eJBD framework
consistently with the general principle of spontaneously broken gauge symmetry,
which makes it possible to confront eJBD-based cosmology with observational and
laboratory bounds on time variation of parameters, masses, and coupling
constants, caused by time evolution of eJBD fields. Decomposition of standard
particle physics lagrangian into independent gauge invariant pieces is proposed
to avoid serious conflict that may arise from standard lagrangian transformed
from the Jordan frame. Independent conformal factors are assigned to each of
five gauge invariant pieces. The formulation is most unambiguously made
possible by defining fields having canonical kinetic terms that allow us to use
the canonical quantization rule of field theory. This construction gives as one
of its consequences the canonical eJBD field $\chi$ that couples to the
universal fermion current, a linear combination of baryon and lepton number
currents, $\partial_{\mu} \chi (\frac{1}{3} j_B^{\mu} + j_L^{\mu})$, in
addition to the conventional trace of the energy-momentum tensor. Field
equation of eJBD field along with gravitational equation is analyzed by using a
simplified polynomial class of potential and conformal functions, giving time
evolution of radiation, matter and dark energy densities consistent with
observations when an appropriate set of model parameters are used. Finite
temperature corrections are further calculated to give temperature dependent
terms in eJBD field potential.

arXiv

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Other Link： http://arxiv.org/pdf/2304.08656v1

Publishing type：Research paper (scientific journal)  

We revisit the calculation of the electron, neutron, and proton electric
dipole moments (EDMs) in the constrained minimal supersymmetric standard model
(CMSSM). The relatively large mass of the Higgs boson, $m_H \simeq 125$ GeV
coupled with the (as yet) lack of discovery of any supersymmetric particle at
the LHC, has pushed the supersymmetry breaking scale to several TeV or higher.
Though one might expect this decoupling to have relaxed completely any bounds
on the two CP violating phases in the CMSSM ($\theta_\mu$ and $\theta_A$), the
impressive experimental improvements in the limits on the EDMs (particularly
the electron EDM) still allow us to set constraints of order $(0.01 - 0.1)\pi$
on $\theta_A$ and $(0.001 - 0.1)\pi$ on $\theta_\mu$. We also discuss the
impact of future improvements in the experimental limits on supersymmetric
models.

DOI： 10.1007/JHEP03(2023)250

arXiv

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Other Link： http://arxiv.org/pdf/2303.02822v1

Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevD.106.075014

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We study the effects of an anomalous Z' boson on the anomalous magnetic
moment of the muon (g-2), and especially the impact of its axial coupling. We
mainly evaluate the negative contribution to (g-2) of such couplings at
one-loop and look at the anomalous couplings generated at two loops. We find
areas of the parameter space, where the anomalous contribution becomes
comparable and even dominant compared to the one-loop contribution. We show
that in such cases, the cutoff of the theory is sufficiently low, so that new
charged fermions can be found in the next round of collider experiments. We
comment on the realization of such a context in string theory orientifolds.

DOI： 10.1007/JHEP02(2023)051

arXiv

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Other Link： http://arxiv.org/pdf/2209.12947v2

Despite its dominance in the present universe's energy budget, dark energy is
the least understood component in the universe. Although there is a popular
model for the dynamical dark energy, the quintessence scalar, the investigation
is limited because of its highly elusive character. We present a model where
the quintessence is gauged by an Abelian gauge symmetry. The quintessence is
promoted to be a complex scalar whose real part is the dark energy field while
the imaginary part is the longitudinal component of a new gauge boson. It
brings interesting characters to dark energy physics. We study the general
features of the model, including how the quintessence behavior is affected and
how the solicited dark energy properties constrain its gauge interaction. We
also note that while the uncoupled quintessence models are suffered greatly
from the Hubble tension, it can be alleviated if the quintessence is under the
gauge symmetry.

DOI： 10.1088/1475-7516/2023/02/005

arXiv

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Other Link： http://arxiv.org/pdf/2208.09229v3

Gravitational particle production is a minimal contribution to reheating the
Universe after the end of inflation. To study this production channel, two
different approaches have commonly been considered, one of which is based on
the Boltzmann equation, and the other is based on the Bogoliubov
transformation. Each of these has pros and cons in practice. The collision term
in the Boltzmann equation can be computed based on quantum field theory in the
Minkowski spacetime, and thus many techniques have been developed so far. On
the other hand, the Bogoliubov approach may deal with the particle production
beyond the perturbation theory and is able to take into account the effect of
the curved spacetime, whereas in many cases one should rely on numerical
methods, such as lattice computation. We show by explicit numerical and
analytical computations of the purely gravitational production of a scalar that
these two approaches give consistent results for particle production with large
momenta during reheating, whereas the Boltzmann approach is not capable of
computing particle production out of vacuum during inflation. We also provide
analytic approximations of the spectrum of produced scalar with/without mass
for the low momentum regime obtained from the Bogoliubov approach.

DOI： 10.1088/1475-7516/2022/09/018

arXiv

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Other Link： http://arxiv.org/pdf/2206.10929v2

We consider the production of dark matter during the process of reheating
after inflation. The relic density of dark matter from freeze-in depends on
both the energy density and energy distribution of the inflaton scattering or
decay products composing the radiation bath. We compare the perturbative and
non-perturbative calculations of the energy density in radiation. We also
consider the (likely) possibility that the final state scalar products are
unstable. Assuming either thermal or non-thermal energy distribution functions,
we compare the resulting relic density based on these different approaches. We
show that the present-day cold dark matter density can be obtained through
freeze-in from preheating for a large range of dark matter masses.

DOI： 10.1088/1475-7516/2022/03/016

arXiv

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Other Link： http://arxiv.org/pdf/2109.13280v1

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

We propose a new portal coupling to dark matter by taking advantage of the
nonminimally coupled portal sector to the Ricci scalar. Such a portal sector
conformally induces couplings to the trace of the energy-momentum tensor of
matters including highly secluded dark matter particles. The portal coupling is
so feeble that dark matter is produced by freeze-in processes of scatterings
and/or the decay of the mediator. We consider two concrete realizations of the
portal: conformally induced Higgs portal and conformally induced mediator
portal. The former case is compatible with the Higgs inflation, while the
latter case can be tested by dark matter direct detection experiments.

DOI： 10.1103/PhysRevD.104.075018

arXiv

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Other Link： http://arxiv.org/pdf/2106.01923v2

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

We show that a metastable dark matter candidate arises naturally from the
conformal transformation between the Einstein metric, where gravitons are
normalised states, and the Jordan metric dictating the coupling between gravity
and matter. Despite being secluded from the Standard Model by a large scale
above which the Jordan metric shows modifications to the Einstein frame metric,
dark matter couples to the energy momentum tensor of the Higgs field in the
primordial plasma primarily. This allows for the production of dark matter in a
sufficient amount which complies with observations. The seclusion of dark
matter makes it long-lived for masses $\lesssim 1$ MeV, with a lifetime much
above the age of the Universe and the present experimental limits. Such a dark
matter scenario has clear monochromatic signatures generated by the decay of
the dark matter candidate into neutrino and/or $\gamma-$rays.

DOI： 10.1103/PhysRevD.103.115016

arXiv

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Other Link： http://arxiv.org/pdf/2103.02615v2

We analyze in detail the perturbative decay of the inflaton oscillating about
a generic form of its potential $V(\phi) = \phi^k$, taking into account the
effects of non-instantaneous reheating. We show that evolution of the
temperature as a function of the cosmological scale factor depends on the spin
statistics of the final state decay products when $k > 2$. We also include the
inflaton-induced mass of the final states leading to either kinematic
suppression or enhancement if the final states are fermionic or bosonic
respectively. We compute the maximum temperature reached after inflation, the
subsequent evolution of the temperature and the final reheat temperature. We
apply our results to the computation of the dark matter abundance through
thermal scattering during reheating. We also provide an example based on
supersymmetry for the coupling of the inflaton to matter.

DOI： 10.1088/1475-7516/2021/04/012

arXiv

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Other Link： http://arxiv.org/pdf/2012.10756v2

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

We generalize dark matter production to a two-metric framework whereby the
physical metric, which couples to the Standard Model (SM), is conformally
and/or disformally related to the metric governing the gravitational dynamics.
We show that this setup is naturally present in many Ultra Violet (UV)
constructions, from K\"ahler moduli fields to tensor-portal models, and from
emergent gravity to supergravity models. In this setting we study dark matter
production in the early Universe resulting from both scatterings off the
thermal bath and the radiative decay of the inflaton. We also take into account
non-instantaneous reheating effects at the end of inflation. In this context,
dark matter emerges from the production of the scalar field mediating the
conformal/disformal interactions with the SM, i.e. realising a Feebly
Interacting Matter Particle (FIMP) scenario where the suppression scale of the
interaction between the scalar and the SM can be taken almost as high as the
Planck scale in the deep UV.

DOI： 10.1103/PhysRevD.103.015028

arXiv

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Other Link： http://arxiv.org/pdf/2011.11647v1

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

We propose a new scenario where dark matter belongs to a secluded sector
coupled to the Standard Model through energy--momentum tensors. Our model is
motivated by constructions where gravity {\it emerges} from a hidden sector,
the graviton being identified by the kinetic term of the fields in the secluded
sector. Supposing that the lighter particle of the secluded sector is the dark
component of the Universe, we show that we can produce it in a sufficiently
large amount despite the suppressed couplings of the theory, thanks to large
temperatures of the thermal bath in the early stage of the Universe.

DOI： 10.1103/PhysRevD.102.055019

arXiv

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Other Link： http://arxiv.org/pdf/2007.06534v2

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

Rare decays of $K$ and $B$ mesons provide a powerful probe of dark sectors
with light new particles. We show that the pair production of $O(100\,{\rm
MeV})$ dark states can be probed with the decays of $K_L$ mesons, owing to the
enhanced two-body kinematics, $K_L\to X_1X_2$ or $X_2X_2$. If either or these
two particles is unstable, e.g. $X_2\to X_1\pi^0$, $X_2\to X_1\gamma$ or
$X_{1,2}\to \gamma\gamma$, such decays could easily mimic $K_L\to \pi^0
\nu\overline{\nu}$ signatures, while not being ruled out by the decays of
charged kaons. We construct explicit models that have enhanced $K_L$ decay
signatures, and are constrained by the results of the KOTO experiment. We note
that recently reported excess events can also be accommodated while satisfying
all other constraints ($B$ decays, colliders, beam dumps). These models are
based on the extensions of the gauge and/or scalar sector of the theory. The
lightest of $X_{1,2}$ particles, if stable, could constitute the entirety of
dark matter.

DOI： 10.1103/PhysRevD.102.055016

arXiv

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Other Link： http://arxiv.org/pdf/2005.07102v2

We perform a systematic analysis of dark matter production during
post-inflationary reheating. Following the period of exponential expansion, the
inflaton begins a period of damped oscillations as it decays. These
oscillations and the evolution of temperature of the thermalized decay products
depend on the shape of the inflaton potential $V(\Phi)$. We consider potentials
of the form $\Phi^k$. Standard matter-dominated oscillations occur for $k=2$.
In general, the production of dark matter may depend on either (or both) the
maximum temperature after inflation, or the reheating temperature, where the
latter is defined when the Universe becomes radiation dominated. We show that
dark matter production is sensitive to the inflaton potential and depends
heavily on the maximum temperature when $k>2$. We also consider the production
of dark matter with masses larger than the reheating temperature.

DOI： 10.1103/PhysRevD.101.123507

arXiv

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Other Link： http://arxiv.org/pdf/2004.08404v2

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

No-scale supergravity provides a successful framework for Starobinsky-like
inflation models. Two classes of models can be distinguished depending on the
identification of the inflaton with the volume modulus, $T$ (C-models), or a
matter-like field, $\phi$ (WZ-models). When supersymmetry is broken, the
inflationary potential may be perturbed, placing restrictions on the form and
scale of the supersymmetry breaking sector. We consider both types of
inflationary models in the context of high-scale supersymmetry. We further
distinguish between models in which the gravitino mass is below and above the
inflationary scale. We examine the mass spectra of the inflationary sector. We
also consider in detail mechanisms for leptogenesis for each model when a
right-handed neutrino sector, used in the seesaw mechanism to generate neutrino
masses, is employed. In the case of C-models, reheating occurs via inflaton
decay to two Higgs bosons. However, there is a direct decay channel to the
lightest right-handed neutrino which leads to non-thermal leptogenesis. In the
case of WZ-models, in order to achieve reheating, we associate the matter-like
inflaton with one of the right-handed sneutrinos whose decay to the lightest
right handed neutrino simultaneously reheats the Universe and generates the
baryon asymmetry through leptogenesis.

DOI： 10.1103/PhysRevD.101.015002

arXiv

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Other Link： http://arxiv.org/pdf/1911.02463v1

Publishing type：Research paper (scientific journal)   Publisher：American Physical Society ({APS})  

We revisit the limits on $R$-parity violation in the minimal supersymmetric
standard model. In particular, we focus on the high-scale supersymmetry
scenario in which all the sparticles are in excess of the inflationary scale of
approximately $10^{13}$ GeV, and thus no sparticles ever come into thermal
equilibrium. In this case the cosmological limits, stemming from the
preservation of the baryon asymmetry that have been previously applied for weak
scale supersymmetry, are now relaxed. We argue that even when sparticles are
never in equilibrium, $R$-parity violation is still constrained via higher
dimensional operators by neutrino and nucleon experiments and/or insisting on
the preservation of a non-zero $B-L$ asymmetry.

DOI： 10.1103/PhysRevD.100.035004

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1905.09243v1

Publishing type：Research paper (scientific journal)  

We compare dark matter production from the thermal bath in the early universe
with its direct production through the decay of the inflaton. We show that even
if dark matter does not possess a direct coupling with the inflaton, Standard
Model loop processes may be sufficient to generate the correct relic abundance.

DOI： 10.1103/PhysRevD.99.063508

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1901.04449v1

Publishing type：Research paper (scientific journal)  

A new setup of cosmic inflation with a periodic inflaton potential and
conformal factor is discussed in the metric and Palatini formulations of
gravity. As a concrete example, we focus on a natural-inflation-like inflaton
potential, and show that the inflationary predictions fall into the allowed
region of cosmic microwave background observations in both formulations.

DOI： 10.1016/j.physletb.2019.03.012

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1812.11077v2

Publishing type：Research paper (scientific journal)  

Gauge coupling unification and the stability of the Higgs vacuum are among
two of the cherished features of low-energy supersymmetric models. Putting
aside questions of naturalness, supersymmetry might only be realised in nature
at very high energy scales. If this is the case, the preservation of gauge
coupling unification and the stability of the Higgs vacuum would certainly
require new physics, but it need not necessarily be at weak scale energies. New
physics near the unification scale could in principle ensure Grand Unification,
while new physics below $\mu \sim 10^{10}$ GeV could ensure the stability of
the Higgs vacuum. Surprisingly however, we find that in the context of a
supersymmetric SO(10) Grand Unified Theory, gauge coupling unification and the
Higgs vacuum stability, when taken in conjunction with existing
phenomenological constraints, require the presence of $\mathcal{O}$(TeV)-scale
physics. This weak-scale physics takes the form of a complex scalar SU(2)$_L$
triplet with zero hypercharge, originating from the $\mathbf{210}$ of SO(10).

DOI： 10.1103/PhysRevD.98.055009

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1807.06488v1

Publishing type：Research paper (scientific journal)  

We consider the effects of R-parity violation due to the inclusion of a
bilinear $\mu^\prime L H_u$ superpotential term in high scale supersymmetric
models with an EeV scale gravitino as dark matter. Although the typical
phenomenological limits on this coupling (e.g. due to lepton number violation
and the preservation of the baryon asymmetry) are relaxed when the
supersymmetric mass spectrum is assumed to be heavy (in excess of the
inflationary scale of $3 \times 10^{13}$ GeV), the requirement that the
gravitino be sufficiently long-lived so as to account for the observed dark
matter density, leads to a relatively strong bound on $\mu^\prime \lesssim 20$
GeV. The dominant decay channels for the longitudinal component of the
gravitino are $Z \nu, W^\pm l^\mp$, and $h\nu$. To avoid an excess neutrino
signal in IceCube, our limit on $\mu'$ is then strengthened to $\mu' \lesssim
50$ keV. When the bound is saturated, we find that there is a potentially
detectable flux of mono-chromatic neutrinos with EeV energies.

DOI： 10.1103/PhysRevD.98.015030

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1805.07342v1

Publishing type：Research paper (scientific journal)  

We construct a self-interacting dark matter model that could simultaneously
explain the observed muon anomalous magnetic moment. It is based on a gauged
U$(1)_{L_{\mu} - L_{\tau } }$ extension of the standard model, where we introduce
a vector-like pair of fermions as the dark matter candidate and a new Higgs
boson to break the symmetry. The new gauge boson has a sizable contribution to
muon $(g-2)$, while being consistent with other experimental constraints. The
U$(1)_{L_{\mu} - L_{\tau } }$ Higgs boson acts as a light force carrier,
mediating dark matter self-interactions with a velocity-dependent cross
section. It is large enough in galaxies to thermalize the inner halo and
explain the diverse rotation curves and diminishes towards galaxy clusters.
Since the light mediator dominantly decays to the U$(1)_{L_{\mu} - L_{\tau } }$
gauge boson and neutrinos, the astrophysical and cosmological constraints are
weak. We study the thermal evolution of the model in the early Universe and
derive a lower bound on the gauge boson mass.

DOI： 10.1007/JHEP06(2018)117

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1805.00651v2

Publishing type：Research paper (scientific journal)  

We study viable small-field Coleman-Weinberg (CW) inflation models with the
help of non-minimal coupling to gravity. The simplest small-field CW inflation
model (with a low-scale potential minimum) is incompatible with the
cosmological constraint on the scalar spectral index. However, there are
possibilities to make the model realistic. First, we revisit the CW inflation
model supplemented with a linear potential term. We next consider the CW
inflation model with a logarithmic non-minimal coupling and illustrate that the
model can open a new viable parameter space that includes the model with a
linear potential term. We also show parameter spaces where the Hubble scale
during the inflation can be as small as $10^{-4} $ GeV, $1$ GeV, $10^4 $ GeV,
and $10^8$ GeV for the number of $e$-folds of $40,~45,~50$, and $55$,
respectively, with other cosmological constraints being satisfied.

DOI： 10.1103/PhysRevD.97.063004

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1708.06455v2

Publishing type：Research paper (scientific journal)  

We propose a realization of cosmic inflation with the Higgs field when the
Higgs potential has degenerate vacua by employing the recently proposed idea of
hillclimbing inflation. The resultant inflationary predictions exhibit a
sizable deviation from those of the ordinary Higgs inflation.

DOI： 10.1103/PhysRevD.97.023523

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1705.03696v2

Publishing type：Research paper (scientific journal)  

We present a new mechanism to produce the dark photon ($\gamma'$) in the
early universe with a help of the axion ($a$) using a recently proposed dark
axion portal. The dark photon, a light gauge boson in the dark sector, can be a
relic dark matter if its lifetime is long enough. The main process we consider
is a variant of the Primakoff process $f a \to f \gamma'$ mediated by a photon,
which is possible with the axion--photon--dark photon coupling. The axion is
thermalized in the early universe because of the strong interaction and it can
contribute to the non-thermal dark photon production through the dark axion
portal coupling. It provides a two-component dark matter sector, and the relic
density deficit issue of the axion dark matter can be addressed by the
compensation with the dark photon. The dark photon dark matter can also address
the reported 3.5 keV $X$-ray excess via the $\gamma' \to \gamma a$ decay.

DOI： 10.1103/PhysRevD.95.115032

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1704.07542v2

Publishing type：Research paper (scientific journal)  

We propose a new class of inflationary models in which inflation takes place
while the inflaton is climbing up a potential hill due to a coupling to
gravity. We study their attractor behavior, and investigate its relation with
known attractors. We also discuss a possible realization of this type of models
with the natural inflation, and show that the inflationary predictions come
well within the region consistent with the observation of the cosmic microwave
background.

DOI： 10.1103/PhysRevD.96.043518

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1703.09020v3

Publishing type：Research paper (scientific journal)  

We study a scenario where sterile neutrino (either warm or cold) dark matter
(DM) is produced through (nonresonant) oscillations among right-handed
neutrinos (RHNs) and can constitute the whole DM in the Universe, in contrast
to the conventional sterile neutrino production through its mixing with the
left-handed neutrinos. The lightest RHN can be sterile neutrino DM whose mixing
with left-handed neutrinos is sufficiently small while heavier RHNs can have
non-negligible mixings with left-handed neutrinos to explain the neutrino
masses by the seesaw mechanism. We also demonstrate that, in our scenario, the
production of sterile RHN DM from the decay of a heavier RHN is subdominant
compared with the RHN oscillation production due to the X-ray and small-scale
structure constraints.

DOI： 10.1103/PhysRevD.97.115021

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1702.04526v2

Publishing type：Research paper (scientific journal)  

The dark photon and the axion (or axion-like particle) are popular light
particles of the hidden sector. Each of them has been actively searched for
through the couplings called the vector portal and the axion portal. We
introduce a new portal connecting the dark photon and the axion
(axion--photon--dark photon, axion--dark photon--dark photon), which emerges in
the presence of the two particles. This dark axion portal is genuinely new
couplings, not just from a product of the vector portal and the axion portal,
because of the internal structure of these couplings. We present a simple model
that realizes the dark axion portal and discuss why it warrants a rich
phenomenology.

DOI： 10.1103/PhysRevLett.118.101802

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1611.01466v3

Publishing type：Research paper (scientific journal)  

We study the right-handed neutrino (RHN) dark matter candidate in the minimal
U(1)_{B-L} gauge extension of the standard model. The U(1)_{B-L} gauge symmetry
offers three RHNs which can address the origin of the neutrino mass, the relic
dark matter, and the matter-antimatter asymmetry of the universe. The lightest
among the three is taken as the dark matter candidate, which is under the B-L
gauge interaction. We investigate various scenarios for this dark matter
candidate with the correct relic density by means of the freeze-out or
freeze-in mechanism. A viable RHN dark matter mass lies in a wide range
including keV to TeV scale. We emphasize the sub-electroweak scale light B-L
gauge boson case, and identify the parameter region motivated from the dark
matter physics, which can be tested with the planned experiments including the
CERN SHiP experiment.

DOI： 10.1007/JHEP02(2017)031

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1606.09317v3

Publishing type：Research paper (scientific journal)  

We discuss a simple model of thermal relic dark matter whose mass can be much
larger than the so-called unitarity limit on the mass of point-like particle
dark matter. The model consists of new strong dynamics with one flavor of
fermions in the fundamental representation which is much heavier than the
dynamical scale of the new strong dynamics. Dark matter is identified with the
lightest baryonic hadron of the new dynamics. The baryonic hadrons annihilate
into the mesonic hadrons of the new strong dynamics when they have large radii.
Resultantly, thermal relic dark matter with a mass in the PeV range is
possible.

DOI： 10.1007/JHEP08(2016)151

Scopus

arXiv

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Other Link： http://arxiv.org/pdf/1606.00159v1

Publishing type：Research paper (scientific journal)  

In the composite Higgs models, originally proposed by Georgi and Kaplan, the
Higgs boson is a pseudo Nambu-Goldstone boson (pNGB) of spontaneous breaking of
a global symmetry. In the minimal version of such models, global SO(5) symmetry
is spontaneously broken to SO(4), and the pNGBs form an isospin doublet field,
which corresponds to the Higgs doublet in the Standard Model (SM). Predicted
coupling constants of the Higgs boson can in general deviate from the SM
predictions, depending on the compositeness parameter. The deviation pattern is
determined also by the detail of the matter sector. We comprehensively study
how the model can be tested via measuring single and double production
processes of the Higgs boson at LHC and future electron-positron colliders. The
possibility to distinguish the matter sector among the minimal composite Higgs
models is also discussed. In addition, we point out differences in the cross
section of double Higgs boson production from the prediction in other new
physics models.

DOI： 10.1103/PhysRevD.94.015028

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arXiv

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Other Link： http://arxiv.org/pdf/1603.05588v1

Publishing type：Research paper (scientific journal)  

Recently there has been a huge interest in the diphoton excess around 750 GeV
reported by both ATLAS and CMS collaborations, although the newest analysis
with more statistics does not seem to support the excess. Nevertheless, the
diphoton channel at the LHC experiments are a powerful tool to probe a new
physics. One of the most natural explanations of a diphoton excess, if it
occurs, could be a new scalar boson with exotic colored particles. In this
setup, it would be legitimate to ask what is the role of this new scalar in
nature. A heavy neutral gauge boson ($Z'$) is one of the traditional targets of
the discovery at the collider experiments with numerous motivations. While the
Landau-Yang theorem dictates the diphoton excess cannot be this spin-1 gauge
boson, there is a strong correlation of a new heavy gauge boson and a new
scalar boson which provides a mass to the gauge boson being at the same mass
scale. In this paper, we point out a simple fact that a new scalar with a
property similar to the recently highlighted 750 GeV would suggest an existence
of a TeV scale $Z'$ gauge boson that might be within the reach of the LHC Run 2
experiments. We take a scenario of the well-motivated and popular gauged $B-L$
symmetry and require the gauge coupling unification to predict the mass and
other properties of the $Z'$ and illustrate the discovery of the $Z'$ would
occur during the LHC experiments.

DOI： 10.1142/S0217751X16501591

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arXiv

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Other Link： http://arxiv.org/pdf/1512.09129v4

Composite Higgs models are an attractive scenario, where the discovered Higgs
boson is regarded as a Nambu-Goldstone boson associated with spontaneous
breakdown of a global symmetry of more fundamental theory. This class of models
predicts violation of perturbative unitarity at high energies, and new
resonances are expected to appear around TeV scale to maintain the unitarity,
while a sizable phase shift is predicted in certain scattering amplitude. We
investigate the new resonance scale from the phase shift by drawing analogies
with pion physics in QCD. The detectability of the phase shift at LHC and the
ILC is also discussed. This talk was given in {\it HPNP 2015} at University of
Toyama and based on the work in collaboration with S.~Kanemura, T.~Shindou and
N.~Machida (arXiv:1410.8413 [hep-ph]).

arXiv

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Other Link： http://arxiv.org/pdf/1504.07966v1

Publishing type：Research paper (scientific journal)  

A novel model of spontaneous Leptogenesis is investigated, where it takes
place in the thermal equilibrium due to a background Nambu-Goldstone field in
motion. In particular, we identify the Nambu-Goldstone field to be the Majoron
which associates with spontaneous breakdown of (discrete) $B-L$ symmetry. In
this scenario sufficient lepton number asymmetry is generated in primordial
thermal bath without having $CP$-violating out-of-equilibrium decay of the
heavy right-handed Majorana neutrinos. To obtain the observed baryon asymmetry,
the neutrino masses are predicted in certain ranges, which can be translated
into the effective mass of the neutrinoless double beta decay.

DOI： 10.1103/PhysRevD.92.035019

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arXiv

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Other Link： http://arxiv.org/pdf/1504.04125v2

Publishing type：Research paper (scientific journal)  

We revisit an extension of the Standard Model with Majorana fermions in the
adjoint representations. There, a precise coupling unification and the good
candidate for dark matter (the $SU(2)_L$ triplet fermion) are achieved
simultaneously. In particular, we show that the $SU(3)_c$ octet fermion which
is required for successful unification can be a good non-thermal source of the
triplet fermion dark matter. We also show that the scenario predicts a rather
short lifetime of the proton compared with the supersymmetric Standard Model,
and the most parameter space can be explored by the future experiments such as
the Hyper-Kamiokande experiment.

DOI： 10.1103/PhysRevD.91.075012

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arXiv

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Other Link： http://arxiv.org/pdf/1411.6044v1

Publishing type：Research paper (scientific journal)  

Composite Higgs models are an intriguing scenario in which the Higgs particle
is identified as a pseudo Nambu-Goldstone boson associated with spontaneous
breaking of some global symmetry above the electroweak scale. They would
predict new resonances at high energy scales, some of which can appear at
multi-TeV scales. In such a case, analogies with pion physics in QCD that a
sizable phase shift is predicted in pion-pion scattering processes might help
us to evaluate scales of the resonances.In this paper, we discuss two
complementary approaches to investigate the compositeness scale in minimal
composite Higgs models. First, we discuss the bound on vector boson scattering
from perturbative unitarity, and we evaluate the phase shift of the scattering
amplitude, assuming that the same fitting function can be applied as the case
in the pion physics. We then obtain the relation between possible phase shifts
and promising new resonance scales. We also investigate the possibility to
measure the phase shift at LHC and the future hadron colliders. Second, we
classify deviations in Higgs coupling constants from the standard model
predictions in various kinds of the minimal composite Higgs models. We then
discuss a possibility to discriminate a specific minimal composite Higgs model
from the other models with extended Higgs sectors by utilizing deviation
patterns in the Higgs boson couplings by future precision measurements.

DOI： 10.1103/PhysRevD.91.115016

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arXiv

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Other Link： http://arxiv.org/pdf/1410.8413v2

Publishing type：Research paper (scientific journal)  

We investigate gravitational effects on the so-called multiple point
criticality principle (MPCP) at the Planck scale. The MPCP requires two
degenerate vacua, whose necessary conditions are expressed by vanishing Higgs
quartic coupling $\lambda(M_{\rm Pl})=0$ and vanishing its $\beta$ function
$\beta_\lambda(M_{\rm Pl})=0$. We discuss a case that a specific form of
gravitational corrections are assumed to contribute to $\beta$ functions of
coupling constants although it is accepted that gravitational corrections do
not alter the running of the standard model (SM) couplings. To satisfy the
above two boundary conditions at the Planck scale, we find that the top pole
mass and the Higgs mass should be $170.8\,{\rm GeV} \lesssim M_t\lesssim
171.7\,{\rm GeV}$ and $M_h=125.7\pm0.4\,{\rm GeV}$, respectively, as well as
include suitable magnitude of gravitational effects (a coefficient of
gravitational contribution as $|a_\lambda| > 2$). In this case, however, since
the Higgs quartic coupling $\lambda$ becomes negative below the Planck scale,
two vacua are not degenerate. We find that $M_h \gtrsim 131.5\,{\rm GeV}$ with
$M_t \gtrsim 174\,{\rm GeV}$ is required by the realization of the MPCP.
Therefore, the MPCP at the Planck scale cannot be realized in the SM and also
the SM with gravity since $M_h \gtrsim 131.5\,{\rm GeV}$ is experimentally
ruled out.

DOI： 10.1103/PhysRevD.91.016004

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arXiv

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Other Link： http://arxiv.org/pdf/1408.5548v2

Publishing type：Research paper (scientific journal)  

The observed neutrino flux can be as a whole well fitted by a simple
power-law of the neutrino energy $E_\nu$, $E_\nu^{-\gamma_\nu}$ ($\gamma_\nu
\simeq 2$). As a notable feature of the spectrum, however, it has a gap between
500 TeV and 1 PeV. Although the existence of the gap in the neutrino spectrum
is not statistically significant at this point, it is very enticing to ask
whether it might hint some physics beyond the Standard Model. In this paper, we
investigate a possibility that the gap can be interpreted as an absorption line
in the power-law spectrum by the cosmic neutrino background through a new
resonance in the MeV range. We also show that the absorption line has rich
information about not only the MeV scale new particle but also the neutrino
masses as well as the distances to the astrophysical sources of the high energy
neutrinos. Viable models to achieve this possibility are also discussed.

DOI： 10.1103/PhysRevD.90.053011

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arXiv

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Other Link： http://arxiv.org/pdf/1407.2848v3

Publishing type：Research paper (scientific journal)  

We discuss the realization of a vanishing effective Higgs potential at the
Planck scale, which is required by the multiple-point criticality principle
(MPCP), in the standard model with singlet scalar dark matter and a
right-handed neutrino. We find the scalar dark matter and the right-handed
neutrino play crucial roles for realization of the MPCP, where a neutrino
Yukawa becomes effective above the Majorana mass of the right-handed neutrino.
Once the top mass is fixed, the MPCP at the (reduced) Planck scale and the
suitable dark matter relic abundance determine the dark matter mass, $m_S$, and
the Majorana mass of the right-handed neutrino, $M_R$, as
$8.5~(8.0)\times10^2~{\rm GeV}\leq m_S\leq1.4~(1.2)\times10^3~{\rm GeV}$ and
$6.3~(5.5)\times10^{13}~{\rm GeV}\leq M_R\leq1.6~(1.2)\times10^{14}~{\rm GeV}$
within current experimental values of the Higgs and top masses. This scenario
is consistent with current dark matter direct search experiments, and will be
checked by future experiments such as LUX with further exposure and/or the
XENON1T.

DOI： 10.1103/PhysRevD.90.036006

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arXiv

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Other Link： http://arxiv.org/pdf/1406.0158v4

Publishing type：Research paper (scientific journal)  

The large value of the tensor-to-scalar ratio in the cosmic microwave
background radiation reported by the BICEP2 collaboration gives strong impact
on models of supersymmetry (SUSY). The large ratio indicates inflation with a
high-energy scale and thus a high reheating temperature in general, and various
SUSY models suffer from the serious gravitino and Polonyi problems. In this
article, we discuss a class of the high-scale SUSY breaking models which are
completely free from those problems. With especially focusing on the dark
matter relic abundance, we examine how the BICEP2 result narrows down the
parameter space of the models, assuming the simplest chaotic inflation model.
We find that the mass of the dark matter is predicted to be less than about 1
TeV thanks to the non-thermal production in the early universe through the
decay of abundant gravitinos produced after the reheating process. We also
discuss implications in some details to dark matter searches at collider and
indirect dark matter detection experiments.

DOI： 10.1007/JHEP07(2014)093

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arXiv

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Other Link： http://arxiv.org/pdf/1403.5880v1

Publishing type：Research paper (scientific journal)  

The high-scale supersymmetry (SUSY) breaking scenario is now attracting many
attentions, because it is consistent with almost all experiments of particle
physics, astrophysics, and cosmology performed so far: e.g. it is possible to
explain the Higgs mass of about 126GeV and contains WIMP dark matter
candidates. In the scenario, gauginos are predicted to be around the TeV scale,
and thus within a kinematically accessible range of near future experiments.
Calculation of the thermal relic abundance for gaugino (bino or wino) dark
matter is then of particular importance in order to clarify its mass consistent
with cosmology and to determine future directions for exploring the high-scale
SUSY breaking scenario. In this article, we calculate the abundance of the
gaugino dark matter, with especially focusing on various coannihilations
between gauginos, which has not been extensively studied so far. Our
calculation involves the Sommerfeld effect on wino and gluino annihilations,
which is known to give significant contributions to their cross sections. Based
on obtained results, we discuss some implications to gaugino searches at
collider and indirect detection experiments of dark matter.

DOI： 10.1103/PhysRevD.89.115021

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arXiv

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Other Link： http://arxiv.org/pdf/1403.0715v2

Publishing type：Research paper (scientific journal)  

We investigate accurate renormalization group analyses in neutrino sector
between $\nu$-oscillation and seesaw energy scales. We consider decoupling
effects of top quark and Higgs boson on the renormalization group equations of
light neutrino mass matrix. Since the decoupling effects are given in the
standard model scale and independent of high energy physics, our method can
basically apply to any models beyond the standard model. We find that the
decoupling effects of Higgs boson are negligible, while those of top quark are
not. Particularly, the decoupling effects of top quark affect neutrino mass
eigenvalues, which are important for analyzing predictions such as mass squared
differences and neutrinoless double beta decay in an underlying theory existing
at high energy scale.

DOI： 10.1016/j.nuclphysb.2014.05.022

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arXiv

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Other Link： http://arxiv.org/pdf/1402.4126v2

Publishing type：Research paper (scientific journal)  

We investigate Planck scale boundary conditions on the Higgs sector of the
standard model with a gauge singlet scalar dark matter. We will find that
vanishing self-coupling and Veltman condition at the Planck scale are realized
with the 126 GeV Higgs mass and top pole mass, 172 GeV $\lesssim M_t\lesssim$
173.5 GeV, where a correct abundance of scalar dark matter is obtained with
mass of 300 GeV $\lesssim m_S \lesssim$ 1 TeV. It means that the Higgs
potential is flat at the Planck scale, and this situation can not be realized
in the standard model with the top pole mass.

DOI： 10.1007/JHEP04(2014)029

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arXiv

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Other Link： http://arxiv.org/pdf/1312.2089v2

Publishing type：Research paper (scientific journal)  

Higgs cubic coupling plays a crucial role to probe an origin of electroweak
symmetry breaking. It is expected that the cubic coupling is measured by Higgs
pair production at the LHC and ILC, and the deviations from the standard model
can be extracted from the Higgs pair production process, and those can give us
a hint of new physics beyond the standard model. We consider a general
potential that achieves the suitable electroweak symmetry breaking. As one of
the interesting models, we suggest a non-perturbative Higgs model in which a
run-away type of potential is used. In the model, the cross sections of pair
production at the LHC is enlarged compared to the standard model. We also study
the Higgs pair production induced by a non-canonical kinetic term of Higgs
fields which will be important to search the pair-production at the ILC.

DOI： 10.1103/PhysRevD.89.015018

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arXiv

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Other Link： http://arxiv.org/pdf/1311.0067v1

Publishing type：Research paper (scientific journal)  

We suggest two types of extension of the standard model, which are the
so-called next to new minimal standard model (NNMSM) type-II and -III. They can
achieve gauge coupling unification as well as suitable dark matter abundance,
small neutrino masses, baryon asymmetry of the universe, inflation, and dark
energy. The gauge coupling unification can be realized by introducing extra two
or three new fields, and could explain the charge quantization. We also show
that there are regions in which the vacuum stability, coupling perturbativity,
and correct dark matter abundance can be realized with current experimental
data at the same time.

DOI： 10.1140/epjc/s10052-013-2696-z

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arXiv

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Other Link： http://arxiv.org/pdf/1309.3254v2

Publishing type：Research paper (scientific journal)  

We suggest a minimal extension of the standard model, which can explain
current experimental data of the dark matter, small neutrino masses and baryon
asymmetry of the universe, inflation, and dark energy, and achieve gauge
coupling unification. The gauge coupling unification can explain the charge
quantization, and be realized by introducing six new fields. We investigate the
vacuum stability, coupling perturbativity, and correct dark matter abundance in
this model by use of current experimental data.

DOI： 10.1016/j.physletb.2014.05.016

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arXiv

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Other Link： http://arxiv.org/pdf/1309.1231v3

Publishing type：Research paper (scientific journal)  

Extra dimension is one of the most attractive candidates beyond the Standard
Model. In warped extra dimensional space-time, not only gauge hierarchy problem
but also quark-lepton mass hierarchy can be naturally explained. In this setup,
a sizable parity violation through Kaluza-Klein gluon exchange appears in QCD
process such as helicity dependent top pair production. We investigate this QCD
parity violating process by use of $SO(5) \times U(1)$ gauge-Higgs unification
model. We evaluate LHC observable quantities, i.e., a charge asymmetry and a
forward-backward asymmetry of the top pair production, and find that a sizable
charge asymmetry can be observed with specific model parameters.

DOI： 10.1103/PhysRevD.87.095002

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arXiv

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Other Link： http://arxiv.org/pdf/1211.5411v2

Publishing type：Research paper (scientific journal)  

We investigate a stability of leptonic self-complementarity such that sum of
three mixing angles in lepton sector is 90 degrees. Renormalization group
equations in a context of minimal supersymmetric standard model for the
self-complementarity are analyzed. It is seen that one of Majorana phases plays
an important role for the stability of self-complementarity. We find some
stable solutions against quantum corrections at a low energy. An effective
neutrino mass for neutrino-less double beta decay is also evaluated by the use
of neutrino parameters giving rise to the stable solutions.

DOI： 10.1209/0295-5075/101/11001

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arXiv

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Other Link： http://arxiv.org/pdf/1209.1522v3

Publishing type：Research paper (scientific journal)  

We investigate a possibility if a loop diagram via Higgsino can enhance the
Higgs to diphoton decay width in supersymmetric models with an extension of
Higgs sector. A model with an additional non-renormalizable term of Higgs
fields is firstly analyzed where the higher order term can introduce the Higgs
coupling to Higgsinos as well as charged Higgs bosons. We point out that a
choice of the Higgs coupling to obtain a significant size of enhancement of
diphoton decay width reduces the Higgs mass and/or a size of non-renormalizable
term needs to be large and a cutoff scale is around the weak scale. Another
model in which the Higgsino mass term is generated by a non-perturbative
instanton effect via a strong dynamics in a context of SUSY QCD is also
suggested. It is shown that the sign of the Higgs coupling to fermions is
opposite from perturbative models due to an operator including bosonic fields
in the denominator and a constructive contribution to the diphoton decay
amplitude can be easily obtained in this kind of model.

DOI： 10.1016/j.physletb.2012.12.049

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arXiv

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Other Link： http://arxiv.org/pdf/1207.5102v3

Publishing type：Research paper (scientific journal)  

Among three typical energy scales, a neutrino mass scale ($m_\nu\sim$ 0.1
eV), a GUT scale ($M_{GUT}\sim 10^{16}$ GeV), and a TeV-scale ($M_{NP}\sim$ 1
TeV), there is a fascinating relation of $M_{NP}\simeq \sqrt{m_\nu\cdot
M_{GUT } }$.The TeV-scale, $M_{NP}$, is a new physics scale beyond the standard
model which is regarded as "supersymmetry" (SUSY) in this letter. We
investigate phenomenology of SUSY SU(5) GUT with neutrinophilic Higgs, which
realizes the above relation dynamically as well as the suitable magnitude of
Dirac mass, $m_\nu$, through a tiny vacuum expectation value of neutrinophilic
Higgs. As a remarkable feature of this model, accurate gauge coupling
unification can be achieved as keeping with a proton stability. We also
evaluate flavor changing processes in quark/lepton sectors.

DOI： 10.1103/PhysRevD.86.015019

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arXiv

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Other Link： http://arxiv.org/pdf/1204.4254v1

Publishing type：Research paper (scientific journal)  

DOI： 10.5506/APhysPolB.43.405

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Among three typical energy scales, a neutrino mass scale (m nu similar to 0.1 eV), a GUT scale (M-GUT similar to 10(16) GeV), and a TeV-scale (M-NP similar to 1 TeV), there is a fascinating relation of M-NP similar or equal to root m nu . M-GUT. The TeV-scale, M-NP, is a new physics scale beyond the standard model which is regarded as "supersymmetry" (SUSY) in this letter. We investigate phenomenology of SUSY SU(5) GUT with neutrinophilic Higgs, which realizes the above relation dynamically as well as the suitable magnitude of Dirac mass, m., through a tiny vacuum expectation value of neutrinophilic Higgs. As a remarkable feature of this model, accurate gauge coupling unification can be achieved as keeping with a proton stability. We also evaluate flavor changing processes in quark/ lepton sectors.

DOI： 10.1063/1.4742109

Web of Science

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We suggest natural TeV-scale seesaw with non-negligible left-right neutrino
mixings as preserving tiny neutrino masses. Our analysis is exhibited, without
loss of generality, by taking a basis of the neutrino matrices, in which the
condition to obtain the left-right mixings is clear. We also suggest a flavor
symmetry as an underlying theory, which naturally realizes our setup to
preserve tiny neutrino masses. Our setup can predict a magnitude of sin
theta_13 in a region of 0.10 to 0.20, depending on the deviation from maximal
atmospheric neutrino mixing and CP phase. We also investigate experimental
constraints and phenomenology in our setup.

arXiv

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Other Link： http://arxiv.org/pdf/1110.2252v1

Publishing type：Research paper (scientific journal)  

Supersymmetric standard model has a parity violation in QCD through chiral
quark-squark-gluino interactions with non-degenerate masses between left-handed
and right-handed squarks. Since experiments have not show any parity violations
in QCD yet, a bound for the mass degeneracy between left-handed and
right-handed squarks should exist. In this paper we try to obtain this bound
for each squark. At first, we investigate a non-degeneracy bound between
$m_{\tilde{c}_L}$ and $m_{\tilde{c}_R}$ from experimental data of charmonium
decay. Next, we estimate the non-degeneracy bounds for $\tilde{u}$ and
$\tilde{d}$ from nucleon-meson scattering data, and comment on other squarks.

DOI： 10.5506/APhysPolB.44.733

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arXiv

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Other Link： http://arxiv.org/pdf/1109.5442v2

Publishing type：Research paper (scientific journal)  

Parity violation in QCD process is studied using helicity dependent top quark
pair productions at Large Hadron Collider experiment. Though no violation can
be found in the standard model (SM), new physics beyond the SM predicts the
violation in general. In order to evaluate the violation, we utilize an
effective operator analysis in a case that new particles predicted by the new
physics are too heavy to be directly detected. By using this method, we try to
discriminate supersymmetric SM from universal extra-dimension model via an
asymmetry measurement of the top quark pair production. We also discuss the
asymmetry from the SM electroweak top pair production process and that from the
little Higgs model.

DOI： 10.1103/PhysRevD.85.014007

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arXiv

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Other Link： http://arxiv.org/pdf/1109.5082v2

Publishing type：Research paper (scientific journal)  

We study the origin of fermion mass hierarchy and flavor mixing in a Lifshitz
type extension of the standard model including an extra scalar field. We show
that the hierarchical structure can originate from renormalizable interactions.
In contrast to the Froggatt-Nielsen mechanism, the higher the dimension of
associated operators, the heavier the fermion masses. Tiny masses for
left-handed neutrinos are obtained without introducing right-handed neutrinos.

DOI： 10.1142/S021773231003327X

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arXiv

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Other Link： http://arxiv.org/pdf/0909.2920v2