Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

Low-energy data, combined with renormalization group (RG) equations, can
predict new physics at far higher energy scales. In this paper, we consider the
possibility that the measured Higgs boson mass and top quark mass hint at a
five-dimensional gauge-Higgs unification (5D GHU) model at a scale above TeV.
We note that the vanishing of the Higgs quartic coupling and the proximity of
the top quark Yukawa coupling and weak gauge coupling at high scales, inferred
from the experimental data, are in harmony with 5D GHU, because in 5D GHU
models the Higgs quartic coupling is forbidden by the 5D gauge symmetry and the
Yukawa couplings and the weak gauge coupling originate from a common 5D gauge
coupling. Based on the above insight, we propose a 5D GHU model where the
Standard Model fermions are embedded in 5D fermions in a way to tightly relate
the top Yukawa coupling with the weak gauge coupling. Also, the model predicts
the presence of vector-like fermions (other than the Kaluza-Klein modes), which
can affect the RG evolutions of the 4D theory and reconcile the scale of
vanishing Higgs quartic coupling and that of equality of the top Yukawa and
weak gauge couplings, thereby achieving a successful matching of the 4D theory
with 5D GHU. We predict the vector-like fermion mass and the compactification
scale of 5D GHU from the conditions for the successful matching.

DOI： 10.1103/PhysRevD.105.015018

Other URL： http://arxiv.org/pdf/2105.03661v1

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

We study colored Higgsino-mediated proton decay (dimension-five proton decay)
in a model based on the flipped $SU(5)$ GUT. In the model, the GUT-breaking
${\bf10}$, ${\bf \overline{10 } }$ fields have a GUT-scale mass term and gain
VEVs through higher-dimensional operators, which induces an effective mass term
between the color triplets in the ${\bf 5}$, ${\bf \bar{5 } }$ Higgs fields that
is not much smaller than the GUT scale. This model structure gives rise to
observable dimension-five proton decay, and at the same time achieves moderate
suppression on dimension-five proton decay that softens the tension with the
current bound on $\Gamma(p\to K^+\nu)$. We investigate the flavor dependence of
the Wilson coefficients of the operators relevant to dimension-five proton
decay, by relating them with diagonalized Yukawa couplings and CKM matrix
components in MSSM, utilizing the fact that the GUT Yukawa couplings are in
one-to-one correspondence with the MSSM Yukawa couplings in flipped models.
Then we numerically evaluate the Wilson coefficients, and predict the
distributions of the ratios of the partial widths of various proton decay
modes.

DOI： 10.1007/JHEP01(2022)061

Other URL： http://arxiv.org/pdf/2110.01198v3

Repository URL： http://hdl.handle.net/10466/0002000080

Publishing type：Research paper (scientific journal)   International / domestic magazine：International journal  

We study a renormalizable SUSY $SO(10)$ GUT model where the Yukawa couplings
of single ${\bf 10}$, single ${\bf \overline{126 } }$ and single ${\bf 120}$
fields, $Y_{10},Y_{126},Y_{120}$, account for the quark and lepton Yukawa
couplings and the neutrino mass. We pursue the possibility that
$Y_{10},Y_{126},Y_{120}$ reproduce the correct quark and lepton masses, CKM and
PMNS matrices and neutrino mass differences, and at the same time suppress
dimension-5 proton decays (proton decays via colored Higgsino exchange) through
their texture, so that the soft SUSY breaking scale can be reduced as much as
possible without conflicting the current experimental bound on proton decays.
We perform a numerical search for such a texture, and investigate implications
of that texture on unknown neutrino parameters, the Dirac CP phase of PMNS
matrix, the lightest neutrino mass and the $(1,1)$-component of the neutrino
mass matrix in the charged lepton basis. Here we concentrate on the case when
the active neutrino mass is generated mostly by the Type-2 seesaw mechanism, in
which case the correlation between the suppression of dimension-5 proton decays
and the neutrino parameters is expected to be most direct.

DOI： 10.1093/ptep/ptaa186

Other URL： http://arxiv.org/pdf/2008.05362v2

Repository URL： http://hdl.handle.net/10466/0002000081

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000087

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000086

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000085

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000089

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000088

We investigate charged lepton flavor violating (CFLV) processes in the
`neutrinophilic Higgs+seesaw model', in which right-handed neutrinos couple
only with an extra Higgs field which develops a tiny VEV and the right-handed
neutrinos also have Majorana mass. The model realizes a seesaw mechanism around
TeV scale without extremely small Dirac Yukawa couplings. A phenomenological
feature of the model is CFLV processes induced by loop diagrams of the charged
scalar particles and heavy neutrinos. Therefore, first we constrain the model's
parameter space from the search for $\mu\to e\gamma$. Next, we predict the
branching ratios of other CFLV processes including the $\mu\to3e$, $\mu+{\rm
Al}\to e+{\rm Al}$, $\mu+{\rm Ti}\to e+{\rm Ti}$, $Z\to e\mu$, $Z\to e\tau$,
$Z\to \mu\tau$, $h\to e\tau$, $h\to\mu\tau$ processes, and discuss their
detectability in future experiments.

DOI： 10.1093/ptep/ptaa089

Other URL： http://arxiv.org/pdf/2004.01896v2

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000091

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000090

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000094

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000095

We investigate a scenario where the supersymmetric partners of two
right-handed neutrinos (sneutrinos) work as mixed inflaton and curvaton,
motivated by the fact that the curvaton contribution to scalar perturbations
can reduce the tensor-to-scalar ratio $r$ so that chaotic inflation models with
a quadratic potential are made consistent with the experimental bound on $r$.
After confirming that the scenario evades the current bounds on $r$ and the
scalar perturbation spectral index $n_s$, we make a prediction on the local
non-Gaussianity in bispectrum, $f_{\rm NL}$, and one in trispectrum, $\tau_{\rm
NL}$. Remarkably, since the sneutrino decay widths are determined by the
neutrino Dirac Yukawa coupling, which can be estimated from the measured active
neutrino mass differences in the seesaw model, our scenario has a strong
predictive power about local non-Gaussianities, as they heavily depend on the
inflaton and curvaton decay rates. Using this fact, we can constrain the
sneutrino mass from the experimental bounds on $n_s$, $r$ and $f_{\rm NL}$.

DOI： 10.1088/1475-7516/2018/06/011

Other URL： http://arxiv.org/pdf/1712.03684v2

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000092

International / domestic magazine：International journal  

Repository URL： http://hdl.handle.net/10466/0002000093

Publishing type：Research paper (scientific journal)  

In the left-right symmetric model based on $SU(2)_L\times SU(2)_R\times
U(1)_{B-L}$ gauge symmetry, there appear heavy neutral scalar particles
mediating quark flavor changing neutral currents (FCNCs) at tree level. We
consider a situation where such FCNCs give the only sign of the left-right
model while $W_R$ gauge boson is decoupled, and name it "semi-aligned two Higgs
doublet model" because the model resembles a two Higgs doublet model with
mildly-aligned Yukawa couplings to quarks. We predict a correlation among
processes induced by quark FCNCs in the model, and argue that future precise
calculation of meson-antimeson mixings and CP violation therein may hint at the
semi-aligned two Higgs doublet model and the left-right model behind it.

DOI： 10.1103/PhysRevD.97.035004

Other URL： http://arxiv.org/pdf/1711.06499v2

The Higgs boson mass and top quark mass imply that the Higgs quartic coupling
vanishes around the scale of $10^9 - 10^{13}$ GeV, depending on the precise
value of the top quark mass. The vanishing quartic coupling can be naturally
addressed if the Higgs field originates from a 5-dimensional gauge field and
the 5th dimension is compactified at the scale of the vanishing Higgs quartic
coupling, which is a scenario based on gauge-Higgs unification. We present a
general prediction of the scenario on the proton decay process $p \to \pi^0
e^+$. In many gauge-Higgs unification models, the 1st generation fermions are
localized towards an orbifold fixed point in order to realize the realistic
Yukawa couplings. Hence, four-fermion operators responsible for the proton
decay can appear with a suppression of the 5-dimensional Planck scale (not the
4-dimensional Planck scale). Since the 5-dimensional Planck scale is connected
to the compactification scale, we have a correlation between the proton partial
decay width and the top quark mass. We show that the future Hyper-Kamiokande
experiment may discover the proton decay if the top quark pole mass is larger
than about 172.5 GeV.

DOI： 10.1103/PhysRevD.94.071701

Other URL： http://arxiv.org/pdf/1608.04065v2

DOI： 10.11316/jpsgaiyo.71.1.0_73

CiNii Article

DOI： 10.11316/jpsgaiyo.71.1.0_42

CiNii Article

DOI： 10.11316/jpsgaiyo.71.1.0_19

CiNii Article

We suggest the so-called bosonic seesaw mechanism in the context of a
classically conformal $U(1)_{B-L}$ extension of the Standard Model with two
Higgs doublet fields. The $U(1)_{B-L}$ symmetry is radiatively broken via the
Coleman-Weinberg mechanism, which also generates the mass terms for the two
Higgs doublets through quartic Higgs couplings. Their masses are all positive
but, nevertheless, the electroweak symmetry breaking is realized by the bosonic
seesaw mechanism. We analyze the renormalization group evolutions for all model
couplings, and find that a large hierarchy among the quartic Higgs couplings,
which is crucial for the bosonic seesaw mechanism to work, is dramatically
reduced toward high energies. Therefore, the bosonic seesaw is naturally
realized with only a mild hierarchy, if some fundamental theory, which provides
the origin of the classically conformal invariance, completes our model at some
high energy, for example, the Planck scale. The requirements for the
perturbativity of the running couplings and the electroweak vacuum stability in
the renormalization group analysis as well as for the naturalness of the
electroweak scale, we have identified the regions of model parameters. For
example, the scale of the $U(1)_{B-L}$ gauge symmetry breaking is constrained
to be $\lesssim 100$ TeV, which corresponds to the extra heavy Higgs boson
masses to be $\lesssim 2$ TeV. Such heavy Higgs bosons can be tested at the
Large Hadron Collider in the near future.

Other URL： http://arxiv.org/pdf/1509.01923v1

There seems to be a non-negligible discrepancy between Daya Bay and T2K
experimental results of a neutrino mixing angle, $\theta_{13}$ . We show the
discrepancy can be simply passed away even in the standard three neutrinos
framework by taking the same value of $\Delta m^2_{32}$ with a normal neutrino
mass hierarchy and Dirac CP phase $\delta = -\pi/ 2$, which is favorable in T2K
experiment. For numerical analyses of neutrino oscillation probabilities, there
are five independent parameters, $\Delta m_{21}^2$, $\Delta m_{32}^2$,
$\theta_{12}$, $\theta_{23}$, and $\delta$. We reevaluate $\theta_{13}$ by
scatter plots within $1 \sigma$ range of five-dimensional parameters space
suggested by PDG, T2K, and Daya Bay. We project onto $\delta$-$\sin^2 2
\theta_{13}$ plane and find an overlap area of $\theta_{13}$ suggested by T2K
and Daya Bay. In the normal hierarchy case, the largest overlap area is given
by parameters set suggested by T2K, and the overlap area becomes small in order
of parameters sets suggested by PDG and Daya Bay. In the inverted hierarchy
case, there is a tiny overlap area only in parameters set suggested by T2K. We
also show several sample points of four parameters set, $\Delta m_{21}^2$,
$\Delta m_{32}^2$, $\theta_{12}$, and $\theta_{23}$, where the dissonance of
$\theta_{13}$ is really disappeared with $\delta = -\pi/2$.

Other URL： http://arxiv.org/pdf/1508.05238v2

DOI： 10.11316/jpsgaiyo.70.1.0_2

CiNii Article

DOI： 10.11316/jpsgaiyo.70.2.0_58

CiNii Article

DOI： 10.11316/jpsgaiyo.70.2.0_46

CiNii Article

DOI： 10.11316/jpsgaiyo.70.2.0_11

CiNii Article

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

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

Publishing type：Research paper (scientific journal)  

We discuss the Higgs inflation scenario with singlet scalar dark matter and a
right-handed neutrino. The singlet scalar and the right-handed neutrino play
crucial roles for realizing a suitable plateau of Higgs potential with the
center value of the top mass of Tevatron and LHC measurements. This Higgs
inflation scenario predicts about a 1 TeV scalar dark matter and an
$\mathcal{O}(10^{14})$ GeV right-handed neutrino by use of 125.6 GeV Higgs
mass, 173.34 GeV top mass, and a nonminimal gravity coupling $\xi\simeq10.1$.
This inflation model is consistent with the recent result of the
tensor-to-scalar ratio $r=0.20_{-0.05}^{+0.07}$ by the BICEP2 Collaboration.

DOI： 10.1103/PhysRevD.89.115009

Other URL： http://arxiv.org/pdf/1404.4737v2

In a class of two Higgs doublet model, where one Higgs doublet generates
masses of quarks and charged leptons whereas the other Higgs doublet with a
tiny vacuum expectation value (VEV) generates neutrino Dirac masses, smallness
of neutrino masses might be understand as the consequence of the small second
Higgs VEV. In this framework, thermal leptogenesis scenarios work well at low
energy scale and have several advantages as follows. Under the assumption of
hierarchical right-handed neutrino masses, the lightest right-handed neutrino
can be as light as ${\cal O}(10^2)$ TeV.The required degeneracy for successful
resonant leptogenesis also can be significantly reduced as small as ${\cal
O}(10^4)$. Availability of low scale thermal leptogenesis provides a novel
solution to gravitino problem in supergravity models.

Other URL： http://arxiv.org/pdf/1401.6646v1

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

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

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

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

Publishing type：Research paper (international conference proceedings)  

We suggest simple models of spontaneous parity violation in supersymmetric strong gauge theory. We focus on left-right symmetric model and investigate vacuum with spontaneous parity violation. Non-perturbative effects are calculable in supersymmetric gauge theory, and we suggest new models. Our models show confinement, so that we try to understand them by using a dual description of the theory. The left-right symmetry breaking and electroweak symmetry breaking are simultaneously occurred with the suitable energy scale hierarchy. This structure has several advantages compared to the MSSM. The scale of the Higgs mass (left-right breaking scale) and that of VEVs are different, so the SUSY little hierarchy problems are absent. The second model also induces spontaneous supersymmetry breaking [1].

DOI： 10.1063/1.4742118

Publishing type：Research paper (international conference proceedings)  

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

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.

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

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

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

Publishing type：Research paper (scientific journal)  

A neutrinophilic Higgs model has tiny vacuum expectation value (VEV), which
can naturally explain tiny masses of neutrinos. There is a large energy scale
hierarchy between a VEV of the neutrinophilic Higgs doublet and that of usual
standard model-like Higgs doublet. In this paper we at first analyze vacuum
structures of Higgs potential in both supersymmetry (SUSY) and non-SUSY
neutrinophilic Higgs models, and next investigate a stability of this VEV
hierarchy against radiative corrections. We will show that the VEV hierarchy is
stable against radiative corrections in both Dirac neutrino and Majorana
neutrino scenarios in both SUSY and non-SUSY neutrinophilic Higgs doublet
models.

DOI： 10.1016/j.physletb.2011.09.103

Other URL： http://arxiv.org/pdf/1107.3203v2

Publishing type：Research paper (scientific journal)  

We investigate a relation among neutrino observables, three mixing angles and
two mass squared differences, from a cascade texture of neutrino mass matrix.
We show an allowed region of the correlation by use of current data of neutrino
oscillation experiments. The relation predicts sharp correlations among
neutrino mixing angles as $0.315\lesssim\sin^2\theta_{12}\lesssim0.332$ and
$0.480\lesssim\sin^2\theta_{23}\lesssim0.500$ with a large $\theta_{13}$
($0.03<\sin^22\theta_{13}<0.28$). These magnitudes are modified
$0.310\lesssim\sin^2\theta_{12}\lesssim0.330$ and
$0.540\lesssim\sin^2\theta_{23}\lesssim0.560$ when the charged lepton mass
matrix also has the cascade form.

DOI： 10.1016/j.physletb.2011.07.029

Other URL： http://arxiv.org/pdf/1106.5926v3

Publishing type：Research paper (scientific journal)  

We investigate thermal leptogenesis in a supersymmetric neutrinophilic Higgs
model by taking phenomenological constraints into account, where, in addition
to the minimal supersymmetric standard model, we introduce an extra Higgs field
with a tiny vacuum expectation value (VEV) which generates neutrino masses.
Thanks to this tiny VEV of the neutrinophilic Higgs, our model allows to reduce
the mass of the lightest right-handed (s)neutrino to be ${\cal O}(10^5)$ GeV as
keeping sufficiently large CP asymmetry in its decay. Therefore, the reheating
temperature after inflation is not necessarily high, hence this scenario is
free from gravitino problem.

DOI： 10.1103/PhysRevD.84.103524

Other URL： http://arxiv.org/pdf/1106.5354v1

Publishing type：Research paper (scientific journal)  

Smallness of neutrino masses can be explained by introducing a tiny vacuum
expectation value of an extra-Higgs doublet which couples to right-handed
neutrinos ($N_R$). This situation is naturally realized in $\nu$-Two Higgs
Doublet Model ($\nu$THDM), where a TeV-scale seesaw mechanism can work well. We
investigate observable phenomenology of $\nu$THDM at LHC and ILC experiments.
Charged Higgs boson ($H^\pm$) in $\nu$THDM is almost originated from the
extra-Higgs doublet and its coupling strength to neutrinos are not small. Then
this model induces rich phenomenology at the LHC, for example, when
$m_{H^\pm}^{} < M_N$, observable charged tracks can be induced from long lived
charged Higgs. On the other hand, when $m_{H^\pm}^{} > M_N$, right-handed
neutrinos can be long-lived, and secondary vertices may be tagged at the LHC.
The $\nu$THDM also predicts observable lepton number violating process at the
ILC.

DOI： 10.1007/JHEP06(2011)068

Other URL： http://arxiv.org/pdf/1105.1409v1

Publishing type：Research paper (scientific journal)  

We suggest simple models of spontaneous parity violation in supersymmetric
strong gauge theory. We focus on left-right symmetric model and investigate
vacuum with spontaneous parity violation. Non-perturbative effects are
calculable in supersymmetric gauge theory, and we suggest two new models. The
first model shows confinement, and the second model has a dual description of
the theory. The left-right symmetry breaking and electroweak symmetry breaking
are simultaneously occurred with the suitable energy scale hierarchy. The
second model also induces spontaneous supersymmetry breaking.

DOI： 10.1007/JHEP08(2011)021

Other URL： http://arxiv.org/pdf/1104.5405v2

Publishing type：Research paper (scientific journal)  

We study a simple five-dimensional extension of the Standard Model,
compactified on a flat line segment in which there propagate Higgs and gauge
bosons of the Standard Model. We impose a Dirichlet boundary condition on the
Higgs field to realize its vacuum expectation value. Since a flat
Nambu-Goldstone zero-mode of the bulk Higgs is eliminated by the Dirichlet
boundary condition, a superposition of the Higgs Kaluza-Klein modes play the
role of the Nambu-Goldstone boson except at the boundaries. We discuss
phenomenology of our model at the LHC, namely the top Yukawa deviation and the
production and decay of the physical Higgs field, as well as the constraints
from the electroweak precision measurements.

DOI： 10.1007/JHEP07(2010)079

DOI： 10.1007/JHEP11(2010)071

Other URL： http://arxiv.org/pdf/1005.2306v3

Publishing type：Research paper (scientific journal)  

DOI： 10.1007/JHEP11(2010)071

Publishing type：Research paper (scientific journal)  

We suggest a simple one-Higgs-doublet model living in the bulk of
five-dimensional spacetime compactified on $S^1/Z_2$, in which the top Yukawa
coupling can be smaller than the naive standard-model expectation, i.e. the top
quark mass divided by the Higgs vacuum expectation value. If we find only
single Higgs particle at the LHC and also observe the top Yukawa deviation, our
scenario becomes a realistic candidate beyond the standard model. The Yukawa
deviation comes from the fact that the wave function profile of the free
physical Higgs field can become different from that of the vacuum expectation
value, due to the presence of the brane-localized Higgs potentials. In the
Brane-Localized Fermion scenario, we find sizable top Yukawa deviation, which
could be checked at the LHC experiment, with a dominant Higgs production
channel being the $WW$ fusion. We also study the Bulk Fermion scenario with
brane-localized Higgs potential, which resembles the Universal Extra Dimension
model with a stable dark matter candidate. We show that both scenarios are
consistent with the current electroweak precision measurements.

DOI： 10.1016/j.nuclphysb.2009.06.024

DOI： 10.1016/j.nuclphysb.2009.09.014

Other URL： http://arxiv.org/pdf/0904.3813v2

Publishing type：Research paper (scientific journal)  

We discuss the scenario with TeV-scale right-handed neutrinos, which are
accessible at future colliders, while holding down tiny seesaw-induced masses
and sizable couplings to the standard-model particles. The signal with
tri-lepton final states and large missing transverse energy is appropriate for
studying collider signatures of the scenario with extra spatial dimensions. We
show that the LHC experiment generally has a potential to discover the signs of
extra dimensions and the origin of small neutrino masses.

DOI： 10.1016/j.physletb.2009.05.042

Other URL： http://arxiv.org/pdf/0901.4596v1

Publishing type：Research paper (scientific journal)  

We study fermion mass matrices of the cascade form which are compatible with the tribimaximal lepton mixing and generation mass hierarchy. The flat-cascade lepton matrices imply a parameter-independent relation among the mixing angles and mass eigenvalues. The relation has several indications that the atmospheric neutrino mixing angle is close to maximal and the other two angles have a correlation independently of neutrino mass eigenvalues. We also discuss phenomenological aspects of the cascade matrices; flavor-violating rare decays of charged leptons, thermal leptogenesis, and leptonic CP violation. Possible dynamical origins of the cascades are illustrated based on flavor symmetry and in higher-dimensional theory.

DOI： 10.1103/PhysRevD.78.113002

Publishing type：Research paper (scientific journal)  

We investigate a construction of five-dimensional (5D) grand unified theories (GUTs) on an interval, which we call iGUTs. We analyze supersymmetric SO(10) iGUT as an example, where the gauge multiplet is spread over the 5D bulk. The SO(10) is directly reduced to the standard model gauge symmetry through the interval boundary conditions. Notice that this rank reduction is impossible in case of GUTs on orbifolds. Four scenarios are possible according to locations (bulk or brane) of Higgs and matter fields. We investigate the gauge-coupling unification, the proton decay, the SO( 10) GUT features such as t-b-tau unification and so on in each scenario. We also comment on the flavor phenomenology.

Publishing type：Research paper (scientific journal)  

We study fermion mass matrices of the cascade form which are compatible with
the tri-bimaximal lepton mixing and generation mass hierarchy. The flat-cascade
lepton matrices imply a parameter-independent relation among the mixing angles
and mass eigenvalues. The relation has several indications that the atmospheric
neutrino mixing angle is close to maximal and the other two angles have a
correlation independently of neutrino mass eigenvalues. We also discuss
phenomenological aspects of the cascade matrices; flavor-violating rare decays
of charged leptons, thermal leptogenesis, and leptonic CP violation. Possible
dynamical origins of the cascades are illustrated based on flavor symmetry and
in higher-dimensional theory.

DOI： 10.1103/PhysRevD.78.113002

Other URL： http://arxiv.org/pdf/0804.4055v4

Publishing type：Research paper (scientific journal)  

We study the five-dimensional SU(3)_c x U(1)_C gauge theory on the orbifold
S^1/Z_2 with a mixed Chern-Simons term. We particularly pay attention to the
realization of the dynamical rearrangement of the theta parameter for SU(3)_c.
It is shown that the physics remains invariant under a large gauge
transformation which even changes the action, completely removing the theta
parameter, because of the Hosotani mechanism for the U(1)_C gauge interactions.
In other words, we show that the theta parameter can be regarded as a boundary
condition for the orbifolding in light of the dynamical rearrangement.

DOI： 10.1103/PhysRevD.78.085021

Other URL： http://arxiv.org/pdf/0803.4380v2

New mechanism of generating flavor mass spectrum is proposed by using an
O'Raifeartaigh-type supersymmetry breaking model. A desired bilinear form of
fermion mass spectrum is naturally realized through F-components of
gauge-singlet (nonet of SU(3) flavor symmetry) superfields, and the suitable
charged-lepton mass relation is reproduced. The charged-slepton mass spectrum
is non-degenerate in general, and can be even hierarchical (proportional to the
charged-lepton masses in the specific case). Flavor changing neutral processes
are suppressed since the charged-lepton and slepton (except for right-handed
sneutrino) mass matrices are diagonalized simultaneously in the flavor space.
The right-handed sneutrinos are light with the similar ratio to the lepton
sector ($\tilde{m}_{\nu_R}$/$\tilde{m}_e \sim m_\nu$/$m_e$).

DOI： 10.1088/1126-6708/2008/06/023

Other URL： http://arxiv.org/pdf/0801.3301v1

We investigate a construction of five-dimensional (5D) grand unified theories
(GUTs) on an interval, which we call iGUTs. We analyze supersymmetric SO(10)
iGUT as an example, where the gauge multiplet is spread over the 5D bulk. The
SO(10) is directly reduced to the standard model gauge symmetry through the
interval boundary conditions. Notice that this rank reduction is impossible in
case of GUTs on orbifolds. Four scenarios are possible according to locations
(bulk or brane) of Higgs and matter fields. We investigate the gauge-coupling
unification, the proton decay, the SO(10) GUT features such as t-b-tau
unification and so on in each scenario. We also comment on the flavor
phenomenology.

DOI： 10.1088/1126-6708/2008/06/044

Other URL： http://arxiv.org/pdf/0801.2635v2

Publishing type：Research paper (scientific journal)  

We construct a model of direct gauge mediation of metastable SUSY breaking by
simply deforming the Intriligator, Seiberg and Shih model in terms of a dual
meson superpotential mass term. No extra matter field is introduced. The
deformation explicitly breaks a U(1)_R symmetry and a pseudo moduli have a
nonzero VEV at one-loop. Our metastable SUSY breaking vacuum turns out to be
sufficiently long-lived. By gauging a subgroup of flavor symmetry, our model
can directly couple to the standard model, which leads to nonvanishing gaugino
mass generation. It is also shown that our model can evade the Landau pole
problem. We show the parameters in the SUSY breaking sector are
phenomenologically constrained.

DOI： 10.1103/PhysRevD.76.115019

Other URL： http://arxiv.org/pdf/0709.2945v2

The charged lepton mass formula can be explained when the masses are
propotinal to the squared vacuum expectation values (VEVs) of scalar fields. We
introduce U(3) flavor symmetry and its nonet scalar field $\Phi$, whose VEV
structure plays an essential role for generating the fermion mass spectrum. We
can naturally obtain bilinear form of the Yukawa coupling
$Y_{ij} \propto \sum_k <\Phi_{ik}> <\Phi_{kj}>$ without the
non-renormalizable interactions, when the flavor symmetry is broken only
through the Yukawa coupling and tadpole terms. We also speculate the possible
VEV structure of $<\Phi>$.

DOI： 10.1016/j.physletb.2007.10.082

Other URL： http://arxiv.org/pdf/0708.3913v2

Publishing type：Research paper (scientific journal)  

We propose a natural framework of
SU(5) supersymmetric grand unified theory with the minimal particle contents,
which does not contain dimension five proton decay operators. The suitable
fermion mass hierarchy can be reproduced by higher dimensional operators of an
adjoint Higgs field which breaks
SU(5) gauge symmetry.

Other URL： http://arxiv.org/pdf/hep-ph/0608244v1

Publishing type：Research paper (scientific journal)  

Supersymmetry broken by anomaly mediation suffers from tachyonic slepton
masses. A possible solution to this problem results in "decoupling", i.e., the
first two generations of sfermions are much heavier than the third one. We note
that in this scenario a sizable loop-induced contribution to the neutrino mass
matrix results. As an application of this scenario we take advantage of the
fact that the decoupling evidently not obeys 2-3 generation exchange symmetry.
In the neutrino sector, this 2-3 symmetry (or mu-tau symmetry) is a useful
Ansatz to generate zero theta_{13} and maximal theta_{23}. The induced
deviations from these values are given for some examples, thereby linking SUSY
breaking to the small parameters (including possibly the solar mass splitting)
of the neutrino sector.

DOI： 10.1103/PhysRevD.74.017701

Other URL： http://arxiv.org/pdf/hep-ph/0603206v1

Publishing type：Research paper (scientific journal)  

We consider several neutrino mass models in an extra-dimensional setting on a
quantitative level. All the models are set in a five-dimensional scenario, with
the standard model (SM) particles living on a brane, while three additional SM
gauge singlets live in the bulk of an extra dimension, which is compactified on
a S^1/Z_2 orbifold. The spontaneous breaking of an additional, continuous U(1)
family symmetry is used to generate suitable neutrino mass matrices via single
right-handed neutrino dominance through the corresponding five-dimensional
extension of the see-saw mechanism. In this manner possible problems of this
combination for some models in four dimensions could be overcome. The
considered models differ with respect to the charges under the family symmetry
and the nature of the five-dimensional Majorana mass term.

DOI： 10.1103/PhysRevD.74.073007

Other URL： http://arxiv.org/pdf/hep-ph/0603158v3

Publishing type：Research paper (scientific journal)  

A new framework for handling flavor symmetry breaking in the neutrino sector
is discussed where the source of symmetry breaking is traced to the global
property of right-handed neutrinos in extra-dimensional space. Light neutrino
phenomenology has rich and robust predictions such as the tri/bi-maximal form
of generation mixing, controlled mass spectrum, and no need of flavor mixing
couplings in the theory.

DOI： 10.1103/PhysRevLett.97.041601

PubMed

Other URL： http://arxiv.org/pdf/hep-ph/0603116v1

The gauge coupling unification is one of main motivations in the split-SUSY
scenario, and the existence of the grand unified theories (GUTs) is assumed. We
examine how to realize split-SUSY mass spectrum in the context of GUTs and find
that the construction of split-SUSY GUTs is by no means straightforward. With
R-symmetry breaking sources in the GUT sector,
GUT particles play a role of the messengers in the gauge mediation scenario
and their contributions to gaugino masses can be sizable. We find the upper
bound on soft scalar masses of
O(10^{10}) GeV from consistency for constructing the split-SUSY GUT. Also, we
discuss the attempt to construct R-symmetric GUT models.

DOI： 10.1143/PTP.116.757

Other URL： http://arxiv.org/pdf/hep-ph/0602013v1

Publishing type：Research paper (scientific journal)  

In supergravity, effective superpotential relevant to dimension five
operators on proton decay processes also leads to supersymmetry breaking terms
among sfermions, dimension four operators. These dimension four operators
induce the dimension five operators through 1-loop diagrams dressed by
gauginos. We find that, in a class of models with the anomaly mediation, the
1-loop contributions can be comparable to those at the tree level. Therefore,
such operators have a great impact on proton decay rate. Depending on a
universal phase of gaugino masses and soft mass spectrum, the proton decay rate
can be enhanced or suppressed.

DOI： 10.1209/0295-5075/82/61001

Other URL： http://arxiv.org/pdf/hep-ph/0601003v3

We propose a scenario of dynamical electroweak symmetry breaking which is
applicable to the model with no tree-level potential for the elementary Higgs
doublet field. An example of such a model is the gauge-Higgs unification model.
The strong coupling "technicolor" dynamics can provide the scale of the
electroweak symmetry breaking in the potential of the Higgs doublet field. The
negative mass squared and quartic coupling can be generated through the Yukawa
couplings among heavy and light "technifermions" and the Higgs doublet field.
Since the massless "technifermion" is singlet under the electroweak gauge
symmetry, no large corrections to the electroweak observables arise. As a
prediction of this scenario, there must be a pseudo-Nambu-Goldstone boson which
couple with the Higgs field in a specific way, though it is singlet under the
standard model gauge symmetry.

Other URL： http://arxiv.org/pdf/hep-ph/0504279v3

Publishing type：Research paper (scientific journal)  

We derive in detail a condition on the Higgs mass parameters that is
necessary for the recently proposed ``split supersymmetry''
(split SUSY) scenario to provide a realistic magnitude of $\tan \beta$. The
nature of this condition can be understood by showing how the Higgs sector of
the minimal supersymmetric Standard Model reduces to that of the Standard Model
in the heavy limit of the soft supersymmetry breaking
Higgs mass parameters. Based on this condition, we present some simple
supersymmetry breaking models that each provides a realistic split-SUSY mass
spectrum, in accordance with the scale of the gravitino mass ($m_{3/2}$) in
relation to those of the soft scalar mass ($\tilde{m}$) and the gaugino mass
($M_{1/2}$) employed in each, namely $m_{3/2} \geq \tilde{m}$, $\tilde{m} \geq
m_{3/2} \geq M_{1/2}$ and $M_{1/2} \geq m_{3/2}$, respectively, with the
relation $\tilde{m} \gg M_{1/2}$ of the split-SUSY mass spectrum.

DOI： 10.1143/PTP.114.1057

Other URL： http://arxiv.org/pdf/hep-ph/0502213v4

Publishing type：Research paper (scientific journal)  

We investigate high-energy behavior of scattering amplitudes in extra dimensional gauge theory where the gauge symmetry is broken by the boundary conditions. We study, in particular, the 5D SU(5) grand unified theory whose 5th-dimensional coordinate is compactified on S-1/Z(2). We pay attention to the gauge symmetry compatible with the boundary conditions on an orbifold and present the BRST formalism of the 4D theory that is obtained through integration of the 5D theory along the extra dimension. We derive the 4D equivalence theorem on the basis of the Slavnov-Taylor identities. We also calculate the amplitudes of the process including four massive gauge bosons in the external lines and compare them with those for the connected reactions in which the gauge fields are replaced by the corresponding would-be Nambu-Goldstone (NG) fields. We explicitly confirm that the equivalence theorem holds.

DOI： 10.24532/soken.110.4_D73

CiNii Article

Publishing type：Research paper (scientific journal)  

We study an ${\cal N}=1$ supersymmetric Yang-Mills theory defined on
$M^4\times S^1$. The vacuum expectation values for adjoint scalar field in
vector multiplet, though important, has been overlooked in evaluating one-loop
effective potential of the theory. We correctly take the vacuum expectation
values into account in addition to the Wilson line phases to give an expression
for the effective potential, and gauge symmetry breaking is discussed. In
evaluating the potential, we employ the Scherk-Schwarz mechanism and introduce
bare mass for gaugino in order to break supersymmetry. We also obtain masses
for the scalars, the adjoint scalar, and the component gauge field for the
$S^1$ direction in case of the SU(2) gauge group. We observe that large
supersymmetry breaking gives larger mass for the scalar. This analysis is
easily applied to the $M^4\times S^1/Z_2$ case.

DOI： 10.1103/PhysRevD.71.025006

Other URL： http://arxiv.org/pdf/hep-th/0411113v2

Publishing type：Research paper (scientific journal)  

Supersymmetric contributions to the neutron electric dipole moment (EDM) are
studied taking account of the flavor changing interactions. We found that the
gluino contribution is sensitive to the flavor changing interaction.
Enhancement of neutron EDM via flavor mixing effects is possible when the
squark mass difference between the different generations is sizable. As an
example, the results of the SUSY SU(5) GUT with right-handed neutrinos are
briefly discussed.

DOI： 10.1142/S0217732305018943

Other URL： http://arxiv.org/pdf/hep-ph/0409243v2

DOI： 10.1103/PhysRevD.70.015010

CiNii Article

Publishing type：Research paper (scientific journal)  

We present an effective flavor model for the radiative generation of fermion
masses and mixings based on a SU(5)xU(2) symmetry. We assume that the original
source of flavor breaking resides in the supersymmetry breaking sector. Flavor
violation is transmitted radiatively to the fermion Yukawa couplings at low
energy through finite supersymmetric threshold corrections. This model can fit
the fermion mass ratios and CKM matrix elements, explain the non-observation of
proton decay, and overcome present constraints on flavor changing processes
through an approximate radiative alignment between the Yukawa and the soft
trilinear sector. The model predicts new relations between dimensionless
fermion mass ratios in the three fermion sectors, and the quark mixing angles.

DOI： 10.1103/PhysRevD.70.055003

Other URL： http://arxiv.org/pdf/hep-ph/0404077v4

Publishing type：Research paper (scientific journal)  

We study the dynamical symmetry breaking in the gauge-Higgs unification of
the 5D ${\mathcal N}=1$ SUSY theory, compactified on an orbifold, $S^1/Z_2$.
This theory identifies Wilson line degrees of freedoms as ``Higgs doublets''.
We consider $SU(3)_c \times SU(3)_W$ and SU(6) models, in which the gauge
symmetries are reduced to $SU(3)_c \times SU(2)_L \times U(1)_Y$ and $SU(3)_c
\times SU(2)_L \times U(1)_Y \times U(1)$, respectively, through the
orbifolding boundary conditions. Quarks and leptons are bulk fields, so that
Yukawa interactions can be derived from the 5D gauge interactions. We estimate
the one loop effective potential of ``Higgs doublets'', and analyze the vacuum
structures in these two models. We find that the effects of bulk quarks and
leptons destabilize the suitable electro-weak vacuum. We show that the
introduction of suitable numbers of extra bulk fields possessing the suitable
representations can realize the appropriate electro-weak symmetry breaking.

DOI： 10.1088/1126-6708/2004/04/016

Other URL： http://arxiv.org/pdf/hep-ph/0402157v2

This paper has been withdrawn by the authors, because the authors have second
thought that the new ideas in this paper are better to be contained in another
paper.

Other URL： http://arxiv.org/pdf/hep-ph/0401184v3

Publishing type：Research paper (scientific journal)  

We show a general formula of the one loop effective potential of the 5D SU(N)
gauge theory compactified on an orbifold, $S^1/Z_2$. The formula shows the case
when there are fundamental, (anti-)symmetric tensor and adjoint
representational bulk fields. Our calculation method is also applicable when
there are bulk fields belonging to higher dimensional representations. The
supersymmetric version of the effective potential with Scherk-Schwarz breaking
can be obtained straightforwardly. We also show some examples of effective
potentials in SU(3), SU(5) and SU(6) models with various boundary conditions,
which are reproduced by our general formula.

DOI： 10.1088/1126-6708/2004/02/059

Other URL： http://arxiv.org/pdf/hep-ph/0401185v4

Publishing type：Research paper (scientific journal)  

We examine the Higgs mass parameters and electroweak symmetry breaking in
supersymmetric orbifold field theories in which the 4-dimensional Higgs fields
originate from higher-dimensional gauge supermultiplets. It is noted that such
gauge-Higgs unification leads to a specific boundary condition on the Higgs
mass parameters at the compactification scale, which is independent of the
details of supersymmetry breaking mechanism. With this boundary condition,
phenomenologically viable parameter space of the model is severely constrained
by the condition of electroweak symmetry breaking for supersymmetry breaking
scenarios which can be realized naturally in orbifold field theories. For
instance, if it is assumed that the 4-dimensional effective theory is the
minimal supersymmetric standard model with supersymmetry breaking parameters
induced mainly by the Scherk-Schwarz mechanism, a correct electroweak symmetry
breaking can not be achieved for reasonable range of parameters of the model,
even when one includes additional contributions to the Higgs mass parameters
from the auxiliary component of 4-dimensional conformal compensator. However if
there exists a supersymmetry breaking mediated by brane superfield, sizable
portion of the parameter space can give a correct electroweak symmetry
breaking.

DOI： 10.1088/1126-6708/2004/02/037

Other URL： http://arxiv.org/pdf/hep-ph/0312178v1

Publishing type：Research paper (scientific journal)  

The dynamical determination of the boundary conditions in SU(N) gauge theory
on the orbifold $S^1/Z_2$ is investigated. We classify the equivalence classes
of the boundary conditions, and then the vacuum energy density of the theory in
each equivalence class is evaluated at one loop order. Unambiguous comparison
of the vacuum energy densities in the two theories in different equivalence
classes becomes possible in supersymmetric theories. It is found that in the
supersymmetric SU(5) models with the Scherk-Schwarz supersymmetry breaking, the
theory with the boundary conditions yielding the standard model symmetry is in
the equivalence class with the lowest energy density, though the low energy
theory is not identically the minimal supersymmetric standard model. We also
study how particular boundary conditions are chosen in the cosmological
evolution of the universe.

DOI： 10.1143/PTP.111.265

Other URL： http://arxiv.org/pdf/hep-ph/0309088v2

Publishing type：Research paper (scientific journal)  

A simple higher dimensional mechanism of the doublet-triplet splitting is
presented in a five dimensional supersymmetric SU(5) GUT on $S^1/Z_2$. The
splitting of multiplets is realized by a mass term of Higgs hypermultiplet
which explicitly breaks SU(5) gauge symmetry. Depending on the sign of mass,
zero mode Higgs doublets and triplets are localized on the either side of the
fixed points. The mass splitting is realized due to the difference of
magnitudes of the overlap with a brane localized or a bulk singlet field. No
unnatural fine-tuning of parameters is needed. The proton stability is ensured
by locality {\em without symmetries}. As well as a conventional mass splitting
solution, it is shown that the weak scale Higgs triplet is consistent with the
proton stability. This result might provide an alternative signature of GUT in
future collider experiments.

DOI： 10.1140/epjc/s2003-01578-4

Other URL： http://arxiv.org/pdf/hep-ph/0306229v2

Publishing type：Research paper (scientific journal)  

We study the unitarity bounds of scattering amplitudes in extra-dimensional gauge theory, in which the gauge symmetry is broken by the boundary conditions. The evaluation of the amplitude of the diagram including four massive gauge bosons in the external lines shows that the asymptotic power behavior of the amplitude is canceled. The calculation is carried out with the 5-dimensional standard model and the SU(5) grand unified theory, whose 5th dimensional coordinate is compactified on S-1/Z(2). The gauge theories broken through the orbifolding preserve unitarity at high energies, similarly to the broken gauge theories in which the gauge bosons acquire masses through the Higgs mechanism. We show that the contributions of the Kaluza-Klein states play a crucial role in conserving the unitarity.

Publishing type：Research paper (scientific journal)  

We suggest simple models which produce the suitable fermion mass hierarchies
and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10)
grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We
introduce 6D and 5D matter fields, which contains the 1st and 2nd generation
matter fields as the zero modes, respectively. The 3rd generation matter fields
are located on a 4D brane. The Yukawa couplings for bulk fields are suppressed
by volume factors from extra dimensions. The suitable fermion mass hierarchies
and flavor mixings are generated by the volume suppression factors.

DOI： 10.1016/S0370-2693(03)00377-0

Other URL： http://arxiv.org/pdf/hep-ph/0212384v1

Publishing type：Research paper (scientific journal)  

We consider 5 dimensional E_6 and E_7 supersymmetric grand unified theories
(GUTs) on an orbifold S^1/Z_2, in which the Higgs fields arise from the 5th
components of the 5D gauge fields. We introduce matter fields in 5 dimensions,
then the Yukawa interactions are induced from the gauge interactions among the
5th component of gauge fields and the bulk hyper-multiplets. The adjoint and
fundamental representations of bulk matter fields can induce all Yukawa
interactions of the standard model in E_6 GUT. Furthermore, realistic fermion
mass hierarchies and flavor mixings with the CP violating phase can be
reproduced by introducing the 4D brane localized fields and their interactions.
E_7 GUT can produce all Yukawa interactions by introducing only adjoint matter
hyper-multiplet in the bulk. The charge quantization and anomaly free structure
on the 4D wall are satisfactory in our models.

DOI： 10.1103/PhysRevD.67.095001

DOI： 10.1103/PhysRevD.69.059902

Other URL： http://arxiv.org/pdf/hep-ph/0212166v2

Publishing type：Research paper (scientific journal)  

Gauge theory defined on the orbifold $M^4 \times (S^1/Z_2)$ is investigated
from the viewpoint of the Hosotani mechanism. Rearrangement of gauge symmetry
takes place due to the dynamics of Wilson line phases. The physical symmetry of
the theory, in general, differs from the symmetry of the boundary conditions.
Several sets of boundary conditions having distinct symmetry can be related by
gauge transformations, belonging to the same equivalence class. The Hosotani
mechanism guarantees the same physics in all theories in one equivalent class.
Examples are presented in the SU(5) theory. Zero modes of the extra-dimensional
components, $A_y$, of gauge fields acquire masses by radiative corrections. In
the nonsupersymmetric SU(5) model the presence of bulk fermions leads to the
spontaneous breaking of color SU(3). In the supersymmetric model with
Scherk-Schwarz SUSY breaking zero modes of $A_y$'s acquire masses of order of
the SUSY breaking.

DOI： 10.1016/S0550-3213(03)00142-1

Other URL： http://arxiv.org/pdf/hep-ph/0212035v3

We suggest simple models which produce the suitable fermion mass hierarchies
and flavor mixing angles based on the 6 dimensional N=1 supersymmetric SO(10)
grand unified theory compactified on a $T^2/(Z_2 \times Z_2')$ orbifold. We
introduce extra vector-like heavy fields in the extra dimensions, and the
suitable fermion mass hierarchies and flavor mixings are generated by
integrating out these heavy fields. We consider gaugino mediation and gauge
mediation supersymmetry breaking mechanisms and their flavor structures. The
experimental constraints of small flavor changing neutral currents suggest
where to locate the supersymmetry breaking brane in the gaugino mediation
mechanism. On the other hand, the SUSY breaking masses are highly degenerated
in the gauge mediation scenario, where the flavor changing neutral currents are
naturally suppressed as in the ordinal four dimensional gauge mediation models.

Other URL： http://arxiv.org/pdf/hep-ph/0210146v3

Publishing type：Research paper (scientific journal)  

We discuss the fermion mass hierarchy and the flavor mixings in the fat brane
scenario of five dimensional SUSY theory. The decoupling solution of the
sfermion mass spectrum can be realized by introducing the vector-like mirror
fields in an extra dimension. In this scenario, both the left- and right-handed
sleptons can have sizable flavor mixings. We point out that this sizable flavor
mixings can induce the suitable magnitude of the muon anomalous magnetic moment
($g_\mu -2$) within the experimental bounds of lepton flavor violating
processes.

DOI： 10.1016/S0370-2693(03)00206-5

Other URL： http://arxiv.org/pdf/hep-ph/0209009v4

Publishing type：Research paper (scientific journal)  

Recently the evidence of the neutrinoless double $\beta$ ($0\nu \beta\beta$)
decay has been announced. This means that neutrinos are Majorana particles and
their mass hierarchy is forced to inverted mass hierarchy (Type B) or
degenerate mass (Type C) patterns in the diagonal basis of charged lepton mass
matrix. We estimate the magnitude of $0\nu \beta\beta$ decay in the degenerate
neutrinos including the cosmological constraint of neutrino dark matter, since
the inverted mass hierarchy pattern always satisfies the cosmological
constraint. The absolute value of neutrino mass is constrained by $0\nu
\beta\beta$ experiment or cosmology depending on the relative signs (Majorana
CP phases) of neutrino masses.

Other URL： http://arxiv.org/pdf/hep-ph/0205141v4

Publishing type：Research paper (scientific journal)  

We suggest simple models which produce the suitable fermion mass hierarchies and flavor mixing angles based on the supersymmetric SO(10) grand unified theory in 6 dimensions compactified on a T-2/Z(2) orbifold. The gauge and Higgs fields propagate in 6 dimensions while ordinal chiral matter fields are localized in 4 dimensions. We introduce extra vector-like heavy fields in the extra dimensions. We show three models according to the configurations of vector-like fields in extra dimensions. The suitable fermion mass hierarchies and flavor mixings are generated by integrating out these vector-like heavy fields. (C) 2002 Elsevier Science B.V All rights reserved.

Publishing type：Research paper (scientific journal)  

We discuss the fermion mass hierarchy and the flavor mixings in the fat brane
scenario of a five dimensional SUSY theory. Assuming that the matter fields
lives in the bulk, their zero mode wave functions are Gaussians, and Higgs
fields are localized on the brane, we find simple various types of the matter
configurations generating the mass matrices consistent with experimental data.
Sfermion mass spectrum is also discussed using the matter configurations found
above. Which type of squark mass spectra (the degeneracy, the decoupling and
the alignment) is realized depends on the relative locations of SUSY breaking
brane and the brane where Higgs fields are localized.

DOI： 10.1103/PhysRevD.66.055005

Other URL： http://arxiv.org/pdf/hep-ph/0204069v1

Publishing type：Research paper (scientific journal)  

We suggest a simple supersymmetric SO(01) and unified theory in 6 dimensions which produces the suitable fermion mass Hierarchies. The 5th- and 6th-dimensional coordinates are compactified on a T-2/Z(2) orbifold. The gauge and I-Eggs fields propagate in 6 dimensions while ordinal chiral matter fields are localized in 4 dimensions. The orbifolding and boundary conditions realize the gauge symmetry reduction, SU(3)(C) x SU(2)(L) x U(l)(Y) x U(1)(X), and the triplet-doublet mass splitting. We introduce extra three sets of vector-like heavy fields: two sets propagate in 6 dimensions and chiral fields which couple to them are defined as the 1st generation, and one set propagates in 5 dimensions and chiral fields which couple to them are defined as the 2nd generation. The suitable fermion mass hierarchies are generated by integrating out these vector-like heavy fields. (C) 2002 Elsevier Science B.V. All rights reserved.

Publishing type：Research paper (scientific journal)  

We discuss the decoupling solution to SUSY flavor problem in the fat brane
scenario. We present a simple model to yield the decoupling sfermion spectrum
in a five dimensional theory. Sfermion masses are generated by the overlap
between the wave functions of the matter fields and the chiral superfields on
the SUSY breaking brane. Two explicit examples of the spectrum are given.

DOI： 10.1142/S0217732302009039

Other URL： http://arxiv.org/pdf/hep-ph/0202196v1

Recently the evidence of the neutrinoless double $\beta$
($0\nu \beta\beta$) decay has been announced. This means that neutrinos are
Majorana particles and their mass hierarchy is forced to certain patterns in
the diagonal basis of charged lepton mass matrix. We estimate the magnitude of
$0\nu \beta\beta$ decay in the classification of the neutrino mass hierarchy
patterns as Type A, $m_{1,2} \ll m_{3}$, Type B,
$m_1 \sim m_2 \gg m_3$, and Type C, $m_1 \sim m_2 \sim m_3$, where $m_{i}$ is
the $i$-th generation neutrino absolute mass. The data of $0\nu \beta\beta$
decay experiment suggests the neutrino mass hierarchy pattern should be Type B
or C. Type B predicts a small magnitude of $0\nu \beta\beta$ decay which is
just edge of the allowed region of experimental value in $95% \mathrm{c.l.}$,
where Majorana CP phases should be in a certain parameter region. Type C can
induce the suitably large amount of $0\nu \beta\beta$ decay which is consistent
with the experimental data, where overall scale of degenerate neutrino mass
plays a crucial role, and its large value can induce the large $0\nu
\beta\beta$ decay in any parameter regions of Majorana CP phases.

DOI： 10.1142/S0217732302007156

Other URL： http://arxiv.org/pdf/hep-ph/0202143v1

We discuss the possibility that the Higgs triplet can be light (1TeV in the
most interesting case) without contradictions with the proton stability %and
the gauge coupling unification in the context of higher dimensional theory. The
proton stability is ensured by the suppression of Yukawa coupling of the Higgs
triplet to the matter through its small overlap of wave functions in extra
dimensions. The light Higgs triplets might be detected in future collider
experiments as an alternative signature of GUT instead of the proton decay. The
gauge coupling unification can be preserved by introducing extra bulk matter
fields.

DOI： 10.1016/S0370-2693(02)01534-4

Other URL： http://arxiv.org/pdf/hep-ph/0201216v2

Publishing type：Research paper (scientific journal)  

We propose a simple grand unified theory in which the fifth dimensional coordinate is compactified oil an S-1/(Z(2) x Z(2)') orbifold. This model is based on the supersymmetric flipped SU(5) x U(1) grand unified theory, which can realize not only the triplet-doublet splitting but also the natural fermion mass hierarchies. The triplet-doublet splitting is realized by S-1/(Z(2) x Z(2)') orbifolding, which also reduces the gauge group as SU(5) x U(1) --&gt; SU(3)(c) x SU(2)(L) x U(1)(z) x U(1)(x). Realistic fermion mass hierarchies are generated by integrating out three extra sets of vector-like heavy fields which can propagate in five dimensions. The radiative corrections too can reduce the gauge group to SU(3)(c) x SU(2)(L) x U(1)(Y) with a simple extension of the model.

Publishing type：Research paper (scientific journal)  

We study the possibility that the lepton-flavor changing process can induce
the suitable magnitude of the muon anomalous magnetic moment (g_\mu -2) in the
decoupling solution to the flavor problem in the minimal supersymmetric
standard model. Our analyses introduce the flavor mixings of left- and
right-handed stau and smuon phenomenologically. It is found that if both the
left- and right-handed sleptons have sizable flavor mixings, the correction to
g_\mu -2 from the lighter slepton can reach to 10^{-9} while the correction to
the branching ratio of \tau \to \mu \gamma satisfies the current experimental
bound. On the other hand, when only the left-handed or right-handed sleptons
have the large flavor mixing, the suitable magnitude of the correction to
g_\mu-2 is not realized owing to the experimental bound of \tau \to \mu \gamma.

DOI： 10.1016/S0370-2693(02)01252-2

Other URL： http://arxiv.org/pdf/hep-ph/0112163v2

Publishing type：Research paper (scientific journal)  

We propose a simple grand unified theory in which the fifth dimensional coordinate is compactified on an S-1/(Z(2) x Z(2)(')) orbifold. We propose two models within this theory, one containing an additional 10 + (10) over bar and one containing an additional 15 + (15) over bar, together with two 24 Higgs multiplets in the non-supersymmetric SU(5) grand unified theory. Although this theory is a non-supersymmetric theory, gauge coupling unification is realized through the mass splittings of Higgs multiplets by S-1/(Z(2) X Z(2)(')) orbifolding. The constraints from b --&gt; sgamma and mu --&gt; egamma and from electron and muon anomalous magnetic moments are also discussed.

Publishing type：Research paper (scientific journal)  

To search for possible textures of lepton mass matrices, we systematically examine flavor mixing structures which can lead to large lepton mixing angles. We find out 37 mixing patterns are consistent with experimental data, taking into account phase factors in the mixing matrices. Only-six of the patterns can explain the observed data without any tuning of parameters, while the others need particular choices for the phase values. It is found that these six mixing patterns are those predicted by the models which have been proposed to account for fermion mass hierarchies. On the other hand, the others may give new flavor mixing structures of lepton mass matrices and therefore new possibilities of model construction.

DOI： 10.1103/PhysRevD.64.113016

Publishing type：Research paper (scientific journal)  

It is well known that the Zee model induces small neutrino masses by radiative corrections, where the bi-maximal flavor mixing is possible. We analyze the cosmological condition in order for the baryon asymmetry generated in the early universe not to be washed out in the Zee model. Since the lepton number is violated explicitly in the Zee model, the baryon asymmetry might be washed out through the sphaleron processes together with the lepton-number violating interactions. In this Letter, we will show that the baryon asymmetry is not washed out, although it has been said that the Zee model cannot preserve the baryon asymmetry generated in the early universe. This can be seen by considering an approximately conserved number, L' equivalent to L-e - L-mu - L-tau. (C) 2001 Published by Elsevier Science B.V.

Publishing type：Research paper (scientific journal)  

We advocate a new approach to study models of fermion masses and mixings, namely, the anarchy proposed by Hall, Murayama, and Weiner. In this approach, we scan the O(1) coefficients randomly. We argue that this is the correct approach when the fundamental theory is sufficiently complicated. Assuming that there is no physical distinction among three generations of neutrinos, the probability distributions in Maki-Nakagawa-Sakata mixing angles can be predicted independent of the choice of the measure. This is because the mixing angles are distributed according to the Haar measure of the Lie groups whose elements diagonalize the mass matrices. The near-maximal mixings, as observed in the atmospheric neutrino data and as required in the large mixing angle solution to the solar neutrino problem, are highly probable. A small hierarchy between Deltam(2) for the atmospheric and the solar neutrinos is obtained very easily; the complex seesaw case gives a hierarchy of a factor of 20 as the most probable one, even though this conclusion is more measure dependent. U-e3 has to be just below the current limit from the CHOOZ experiment. The CP-violating parameter sin delta is preferred to be maximal. We present a simple SU(5)-like extension of anarchy to the charged lepton and quark sectors that works well phenomenologically.

DOI： 10.24532/soken.102.4_D86

CiNii Article

Publishing type：Research paper (scientific journal)  

Neutrino-oscillation solutions for the atmospheric neutrino anomaly and the solar neutrino deficit carl determine the texture of the neutrino mass matrix according to three types of neutrino mass hierarchy: Type A: m(1) &lt;&lt; m(2) &lt;&lt; m(3), Type B: m(1) similar to m(2) &gt;&gt; m(3), and Type C: m(1) similar to m(2) similar to m(3), where m(i) is the absolute mass of the ith generation neutrino. The relative sign assignments of the neutrino masses in each type of mass hierarchy play crucial roles in the stability against quantum corrections. Actually, two physical Majorana phases in the lepton flavor mixing matrix connect the relative sign assignments of the neutrino masses. Therefore, in this paper me analyze the stability of the mixing angles against quantum corrections according to three types of neutrino mass hierarchy (Type A, B, C) and two Majorana phases. The two phases play crucial roles in the stability of the mixing angles against quantum corrections.

DOI： 10.1007/s100520000458

We advocate a new approach to study models of fermion masses and mixings,
namely anarchy proposed in hep-ph/9911341. In this approach, we scan the O(1)
coefficients randomly. We argue that this is the correct approach when the
fundamental theory is sufficiently complicated. Assuming there is no physical
distinction among three generations of neutrinos, the probability distributions
in MNS mixing angles can be predicted independent of the choice of the measure.
This is because the mixing angles are distributed according to the Haar measure
of the Lie groups whose elements diagonalize the mass matrices. The
near-maximal mixings, as observed in the atmospheric neutrino data and as
required in the LMA solution to the solar neutrino problem, are highly
probable. A small hierarchy between the Delta m^2 for the atmospheric and the
solar neutrinos is obtained very easily; the complex seesaw case gives a
hierarchy of a factor of 20 as the most probable one, even though this
conclusion is more measure-dependent. U_{e3} has to be just below the current
limit from the CHOOZ experiment. The CP-violating parameter sin delta is
preferred to be maximal. We present a simple SU(5)-like extension of anarchy to
the charged-lepton and quark sectors which works well phenomenologically.

DOI： 10.1103/PhysRevD.63.053010

Other URL： http://arxiv.org/pdf/hep-ph/0009174v1

Publishing type：Research paper (scientific journal)  

We investigate whether the lepton flavor mixing angles in the so-called democratic type of mass matrix are stable against quantum corrections or not in the minimal supersymmetric standard model with dimension five operator which induces neutrino mass matrix. By taking simple breaking patterns of S-3L x S-3R or O(3)(L) x O(3)(R) flavor symmetries and the scale where democratic textures are induced as O(10(13)) GeV, we find that the stability of the lepton flavor mixing angles in the democratic type of mass matrix against quantum corrections depends on the solar neutrino solutions, The maximal flavor mixing of the Vacuum oscillation solution is spoiled by quantum corrections in the experimental allowed region of tan beta, The large angle MSW solution is spoiled by quantum corrections in the region of tan beta &gt; ra. The condition of tan beta less than or equal to 10 is needed in order to obtain the suitable mass squared difference of the small angle MSW solution, These strong constraints must be regarded for the model building of the democratic type of mass matrix. (C) 2000 Published by Elsevier Science B.V.

DOI： 10.1016/S0370-2693(00)00911-4

Publishing type：Research paper (scientific journal)  

Recent neutrino experiments suggest strong evidence of tiny neutrino masses and the lepton-flavor mixing. Neutrino-oscillation solutions for the atmospheric neutrino anomaly and the solar neutrino deficit can determine the texture of the neutrino mass matrix according to the neutrino mass hierarchies as Type A: m(3) much greater than m(2) similar to m(1), Type B: m(3) much less than m(2) similar to m(1), and Type C: m(3) similar to m(2) similar to m(1), where mi is the i-th generation neutrino mass. In this paper we study the stability of the lepton-flavor mixing matrix against quantum corrections for all three types of mass hierarchy in the minimal supersymmetric Standard Model with an effective dimension-five operator which gives the Majorana masses of neutrinos. The relative sign assignments of neutrino masses in each type play crucial role for the stability against quantum corrections. We find that the lepton-flavor mixing matrix of Type A is stable against quantum corrections, and that of Type B with the same (opposite) signs of mi and ma are unstable (stable). For Type C, the lepton-flavor-mixing matrix approaches the definite unitary matrix according to the relative sign assignments of the neutrino mass eigenvalues as the effects of quantum corrections become large enough to neglect the squared mass differences of neutrinos.

DOI： 10.1007/s100520000333

Publishing type：Research paper (scientific journal)  

We examine the dynamics induced on the four dimensional boundary of a five dimensional anti-deSitter spacetime by the five dimensional Chern-Simons theory with gauge group the direct product of SO(4,2) with U(1). We show that, given boundary conditions compatible with the geometry of 5d AdS spacetime in the asymptotic region, the induced surface theory is the WZW4 model. (C) 2000 Elsevier Science B.V.

DOI： 10.1016/S0370-2693(00)00271-9

Publishing type：Research paper (scientific journal)  

It is well known that Zee type neutrino mass matrix can provide bi-maximal neutrino mixing for three neutrinos. We study the reconciliation of this model with the gauge mediated supersymmetry breaking scenario, which naturally suppresses the large flavor changing neutral current and CP violation in the supersymmetric standard model. When the messenger fields have suitable B-L charges, the radiative correction naturally induces the Zee neutrino mass matrix, which provides tiny neutrino masses and large lepton flavor mixings. Our numerical results are consistent with the neutrino oscillation experiments in both three and four neutrino models. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Publishing type：Research paper (scientific journal)  

In the case of two-generation neutrinos, the energy-scale dependence of the lepton-flavor mixing matrix with Majorana phase can be governed by only one parameter, r, which is the ratio between the diagonal elements of the neutrino mass matrix. By using this parameter, we derive the analytic solutions to the renormalisation group equations of the physical parameters, which are the mixing angle, the Majorana phase, and the ratio of the mass-squared difference to the mass squared of the heaviest neutrino. The energy-scale dependence of the Majorana phase is clarified by using these analytic solutions. The instability of the Majorana phase arises in the same parameter region in which the mixing angle is unstable with respect to quantum corrections.

DOI： 10.1143/PTP.103.807

Publishing type：Research paper (scientific journal)  

The Superkamiokande experiment suggests large flavor mixing between nu(mu) and nu(tau). We show that both the second and third generation neutrino masses are larger than O(0.1 eV) when the mixing angle receives significant corrections from the renormalization group equation (RGE). This implies that this mixing angle must be small at the right-handed neutrinos' decoupling scale when the results of the LSND experiments are correct and when the atmospheric neutrino anomaly is accounted for by nu(mu)-nu(tau) oscillation.

Publishing type：Research paper (scientific journal)  

There are physical Majorana phases in the lepton flavor mixing matrix when neutrinos are Majorana fermions. In the case of two degenerate neutrinos, the physical Majorana phase plays a crucial role in the stability of the maximal flavor mixing between the second and the third generations with respect to quantum corrections. The physical Majorana phase of pi guarantees that the maximal mixing is stable with respect to quantum corrections, while the Majorana phase of zero causes the maximal mixing destroyed by quantum corrections when neutrino masses are of O(1 eV). The continuous change of the Majorana phase from pi to 0 makes the maximal mixing destroyed by quantum corrections with O(1 eV) degenerate neutrino masses. On the other hand, when there is a large mass hierarchy among neutrinos, the maximal flavor mixing is not destroyed by quantum corrections independently of the Majorana phase.

DOI： 10.1143/PTP.103.145

Publishing type：Research paper (scientific journal)  

We study an energy-scale dependence of the lepton flavor-mixing matrix in the minimal supersymmetric standard model with the effective dimension-five operators, which give Majorana masses of neutrinos. We analyze the renormalization group equations of the coefficients (K-ij) of these effective operators under an approximation that neglects terms of order K-2. We find that only n(g) - 1 (where n(g) is the generation number) real independent parameters in the lepton flavor-mixing matrix depend on the energy scale. In particular, all the phases in k are scale-independent.

DOI： 10.24532/soken.100.3_C60

CiNii Article

Publishing type：Research paper (scientific journal)  

The singular seesaw mechanism can naturally explain the atmospheric neutrino
deficit by the maximal oscillation between $\nu_{\mu_L}$ and $\nu_{\mu_R}$.
This mechanism can also induce three different scales of neutrino mass squared
differences, which can explain the neutrino deficits of three independent
experiments (solar, atmospheric, and LSND) by neutrino oscillations. In this
paper we show that the realistic mixing angles among neutrinos can be obtained
by introducing the hierarchy in the Dirac neutrino mass. In the case where
Majorana neutrino mass matrix has rank 2, the solar neutrino deficit is
explained by the vacuum oscillation between $\nu_e$ and $\nu_\tau$. We also
consider the case where Majorana neutrino mass matrix has rank 1. In this case,
the mater enhanced Mikheyev-Smirnov-Wolfenstein solar neutrino solution is
prefered as the solution of the solar neutrino deficit.

DOI： 10.1007/s100520000397

Other URL： http://arxiv.org/pdf/hep-ph/9808254v3

Publishing type：Research paper (scientific journal)  

The sliding singlet mechanism is one of the most interesting solutions of the
triplet-doublet splitting problem. We analyze this mechanism in the gauge
mediated supersymmetry breaking scenario. We show that the sliding singlet
mechanism does not work in the naive gauge mediation scenario because of the
singlet linear terms derived from the gravity, although $F$ term is much
smaller than the one in the gravity mediation scenario. We also consider the
extension in order for the sliding singlet mechanism to work.

DOI： 10.1103/PhysRevD.59.055002

Other URL： http://arxiv.org/pdf/hep-ph/9804279v3

It has been pointed out that the mixing of an eV-scale sterile neutrino with
active flavors can lead to loss of sensitivity to the $\theta_{23}$ octant
(sign of $\sin^2\theta_{23}-1/2$) in long baseline experiments, because the
main oscillation probability
$P_0=4\sin^2\theta_{23}\sin^2\theta_{13}\sin^2\Delta_{31}$ can be degenerate
with the sum of the interferences with the solar oscillation amplitude and an
active-sterile oscillation amplitude in both neutrino and antineutrino
oscillations, depending on CP phases. In this paper, we show that the above
degeneracy is resolved by measuring the same beam at different baseline
lengths. We demonstrate that Tokai-to-Hyper-Kamiokande-to-Korea (T2HKK)
experiment (one 187~kton fiducial volume water Cerenkov detector is placed at
Kamioka, $L=295$~km, and another detector is put in Korea, $L\sim1000$~km)
exhibits a better sensitivity to the $\theta_{23}$ octant in those parameter
regions where the experiment with two detectors at Kamioka is insensitive to
it. Therefore, if a hint of sterile-active mixings is discovered in short
baseline experiments, T2HKK is a better option than the plan of placing two
detectors at Kamioka. We also consider an alternative case where one detector
is placed at Kamioka and a different detector is at Oki Islands, $L=653$~km,
and show that this configuration also leads to a better sensitivity to the
$\theta_{23}$ octant.

DOI： 10.1103/PhysRevD.101.075034

Other URL： http://arxiv.org/pdf/1812.10940v2

In preparation for upcoming nucleon decay searches at Hyper-Kamiokande, it is
important to derive a theoretical upper bound on the proton lifetime in a
general class of grand unified theory (GUT) models. In this paper, we make an
attempt along this direction for non-SUSY SU(5) models, under the mild
restrictions that only one or two SM-decomposed multiplets are singularly
light, and that the SU(5) gauge theory is asymptotically free and thus there
are no too large representations in the model. We derive criteria for
SM-decomposed multiplets that potentially enhance the proton lifetime when they
are singularly light. We perform a numerical analysis on the proton lifetime
and show that some choices of singularly light multiplets can provide a
testable upper bound on the proton lifetime.

DOI： 10.1103/PhysRevD.99.075018

Other URL： http://arxiv.org/pdf/1812.08521v2

In preparation for upcoming nucleon decay searches at Hyper-Kamiokande, it is
important to derive a theoretical upper bound on the proton lifetime in a
general class of grand unified theory (GUT) models. In this paper, we make an
attempt along this direction for non-SUSY SU(5) models, under the mild
restrictions that only one or two SM-decomposed multiplets are singularly
light, and that the SU(5) gauge theory is asymptotically free and thus there
are no too large representations in the model. We derive criteria for
SM-decomposed multiplets that potentially enhance the proton lifetime when they
are singularly light. We perform a numerical analysis on the proton lifetime
and show that some choices of singularly light multiplets can provide a
testable upper bound on the proton lifetime.

DOI： 10.1103/PhysRevD.99.075018

Since the standard model contribution is virtually absent, any observation of
direct CP violation in the Cabibbo-favored charmed meson decays would be
evidence of new physics. In this paper, we conduct a quantitative study on
direct CP violation in $D^0\to K^-\pi^+$, $D_s^+\to \eta\pi^+$ and $D_s^+\to
\eta'\pi^+$ decays in the $SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ gauge
extension of the standard model. In the model, direct CP violation arises
mainly from the interference between the decay amplitude coming from the SM
left-left current operators and that from the right-right current operators
induced by $W_R^+$ gauge boson exchange. Interestingly, the strong phase
between the two amplitudes is evaluable, since it stems from difference in QCD
corrections to the left-left and right-right current operators, which is a
short-distance QCD effect given by
$\sim(\alpha_s(M_{W_L}^2)/4\pi)\log(M_{W_R}^2/M_{W_L}^2)$. We assess the
maximal direct CP violation in the above decays in the $SU(2)_L\times
SU(2)_R\times U(1)_{B-L}$ model. Additionally, we present a correlation between
direct CP violation in these modes and one in $K\to\pi\pi$ decay parametrized
by $\epsilon'$, since $W_R^+$ gauge boson has a sizable impact on the latter.

DOI： 10.1007/JHEP10(2018)006

Other URL： http://arxiv.org/pdf/1806.03424v3

The Standard Model prediction for $\epsilon'/\epsilon$ based on recent
lattice QCD results exhibits a tension with the experimental data. We solve
this tension through $W_R^+$ gauge boson exchange in the $SU(2)_L\times
SU(2)_R\times U(1)_{B-L}$ model with `charge symmetry', whose theoretical
motivation is to attribute the chiral structure of the Standard Model to the
spontaneous breaking of $SU(2)_R\times U(1)_{B-L}$ gauge group and charge
symmetry. We show that $M_{W_R}<58$ TeV is required to account for the
$\epsilon'/\epsilon$ anomaly in this model. Next, we make a prediction for the
neutron EDM in the same model and study a correlation between
$\epsilon'/\epsilon$ and the neutron EDM. We confirm that the model can solve
the $\epsilon'/\epsilon$ anomaly without conflicting the current bound on the
neutron EDM, and further reveal that almost all parameter regions in which the
$\epsilon'/\epsilon$ anomaly is explained will be covered by future neutron EDM
searches, which leads us to anticipate the discovery of the neutron EDM.

DOI： 10.1007/JHEP05(2018)052

Other URL： http://arxiv.org/pdf/1802.09903v3

In Type-I seesaw model, the lepton flavor mixing matrix (PMNS matrix) and the
quark flavor mixing matrix (CKM matrix) may be connected implicitly through a
relation between the neutrino Dirac Yukawa coupling $Y_D$ and the quark Yukawa
couplings. In this paper, we study whether $Y_D$ can satisfy, in the flavor
basis where the charged lepton Yukawa and right-handed neutrino Majorana mass
matrices are diagonal, the relation $Y_D \propto {\rm
diag}(y_d,y_s,y_b)V_{CKM}^T$ or $Y_D \propto {\rm diag}(y_u,y_c,y_t)V_{CKM}^*$
without contradicting the current experimental data on quarks and neutrino
oscillations. We search for sets of values of the neutrino Dirac CP phase
$\delta_{CP}$, Majorana phases $\alpha_2,\alpha_3$, and the lightest active
neutrino mass that satisfy either of the above relations, with the normal or
inverted hierarchy of neutrino mass. In performing the search, we consider
renormalization group evolutions of the quark masses and CKM matrix and the
propagation of their experimental errors along the evolutions. We find that
only the former relation $Y_D \propto {\rm diag}(y_d,y_s,y_b)V_{CKM}^T$ with
the normal neutrino mass hierarchy holds, based on which we make a prediction
for $\delta_{CP},\,\alpha_2,\,\alpha_3$ and the lightest active neutrino mass.

DOI： 10.1103/PhysRevD.97.055018

Other URL： http://arxiv.org/pdf/1801.02904v2

DOI： 10.1088/1475-7516/2018/06/011

We study the discovery potential for the mixing of heavy isospin-singlet
neutrinos in extensions of the Tokai-to-Kamioka (T2K) experiment: The
Tokai-to-Hyper-Kamiokande (T2HK), the Tokai-to-Hyper-Kamiokande-to-Korea
(T2HKK), and a plan of adding a new detector at Oki Islands to the T2HK. We
parametrize the mixing of heavy neutrinos in terms of a non-unitary mixing
matrix acting on active flavors. It is shown that in the T2HK and T2HKK, the
sensitivity to heavy neutrino mixing deteriorates for some values of
$CP$-violating phases in the standard and the non-unitary mixing matrices, but
the deterioration is drastically mitigated if a detector at Oki Islands is
added to the T2HK. We also consider the feasibility of measuring the mass
hierarchy and the standard $CP$-violating phase $\delta_{CP}$ in the presence
of heavy neutrino mixing, by fitting experimental data with the standard
oscillation parameters only, i.e., under the assumption of unitary mixing. It
is revealed that such measurement can be performed to some accuracy in the
T2HKK and the extension of the T2HK with a detector at Oki Islands, owing to
the fact that data with largely varying $L/E$ are collected in these
experiments, while it cannot be in the T2HK.

DOI： 10.1140/epjc/s10052-017-5294-7

Other URL： http://arxiv.org/pdf/1705.03818v3

We present a novel extension of the Standard Model which fulfills the
multiple-point principle without contradicting the Higgs particle mass
measurement. In the model, the scalar potential has two minima where the scalar
field has vacuum expectation values of 246 GeV and the Planck mass $\simeq
2.44\times 10^{18}$ GeV, the latter of which is realized by considering a
classically scale invariant setup and requiring that the scalar quartic
coupling and its beta function vanish at the Planck scale. The Standard Model
Higgs field is a mixture of an elementary scalar and composite scalars in a new
strongly-coupled gauge theory, and the strong dynamics gives rise to the
negative mass for the SM Higgs field, and at the same time, causes separation
of the SM Higgs quartic coupling and the quartic coupling for the elementary
scalar, which leads to the vanshing of the latter quartic coupling and its beta
function at the Planck scale. The model predicts new scalar particles with
about 300 GeV mass possessing electroweak charges and Yukawa-type couplings
with Standard Model fermions, and a new light gauge boson that couples to
Standard Model fermions.

DOI： 10.1103/PhysRevD.95.115015

Other URL： http://arxiv.org/pdf/1703.04235v2

We investigate the scenario where the Standard Model is extended with
classical scale invariance, which is broken by chiral symmetry breaking and
confinement in a new strongly-coupled gauge theory that resembles QCD. The
Standard Model Higgs field emerges as a result of the mixing of a scalar meson
in the new strong dynamics and a massless elementary scalar field. The mass and
scalar decay constant of that scalar meson, which are generated dynamically in
the new gauge theory, give rise to the Higgs field mass term, automatically
possessing the correct negative sign by the bosonic seesaw mechanism. Using
analogy with QCD, we evaluate the dynamical scale of the new gauge theory and
further make quantitative predictions for light pseudo-Nambu-Goldstone bosons
associated with axial symmetry breaking along chiral symmetry breaking in the
new gauge theory. A prominent consequence of the scenario is that there should
be a Standard Model gauge singlet pseudo-Nambu-Goldstone boson with mass below
220GeV, which couples to two electroweak gauge bosons through the
Wess-Zumino-Witten term, whose strength is thus determined by the dynamical
scale of the new gauge theory. Other pseudo-Nambu-Goldstone bosons, charged
under the electroweak gauge groups, also appear. Concerning the theoretical
aspects, it is shown that the scalar quartic coupling can vanish at the Planck
scale with the top quark pole mass as large as 172.5GeV, realizing the flatland
scenario without being in tension with the current experimental data.

DOI： 10.1103/PhysRevD.95.115016

Other URL： http://arxiv.org/pdf/1701.02146v4

The Higgs boson mass and top quark mass imply that the Higgs quartic coupling vanishes around the scale of 10(9)-10(13) GeV, depending on the precise value of the top quark mass. The vanishing quartic coupling can be naturally addressed if the Higgs field originates from a five-dimensional gauge field and the fifth dimension is compactified at the scale of the vanishing Higgs quartic coupling, which is a scenario based on gauge-Higgs unification. We present a general prediction of the scenario on the proton decay process p -&gt; pi(0)e(+). In many gauge-Higgs unification models, the first-generation fermions are localized towards an orbifold fixed point in order to realize the realistic Yukawa couplings. Hence, four-fermion operators responsible for the proton decay can appear with a suppression of the five-dimensional Planck scale (not the four-dimensional Planck scale). Since the five-dimensional Planck scale is connected to the compactification scale, we have a correlation between the proton partial decay width and the top quark mass. We show that the future Hyper-Kamiokande experiment may discover the proton decay if the top quark pole mass is larger than about 172.5 GeV.

DOI： 10.1103/PhysRevD.94.071701

We introduce three right-handed neutrinos and three sterile neutrinos, and
consider an inverse seesaw mechanism for neutrino mass generation. From
naturalness point of view, their Majorana masses should be small, while it
induces a large neutrino Yukawa coupling. Then, a neutrinoless double beta
decay rate can be enhanced, and a sizable Higgs mass correction is inevitable.
We find that the enhancement rate can be more than ten times compared with a
standard prediction from light neutrino contribution alone, and an analytic
form of heavy neutrino contributions to the Higgs mass correction. In addition,
we numerically analyze the model, and find almost all parameter space of the
model can be complementarily searched by future experiments of neutrinoless
double beta decay and $\mu \to e$ conversion.

DOI： 10.1007/JHEP11(2016)003

Other URL： http://arxiv.org/pdf/1608.07447v2

We suggest a scalar singlet extension of the standard model, in which the
multiple-point principle (MPP) condition of a vanishing Higgs potential at the
Planck scale is realized. Although there have been lots of attempts to realize
the MPP at the Planck scale, the realization with keeping naturalness is quite
difficult. Our model can easily achieve the MPP at the Planck scale without
large Higgs mass corrections. It is worth noting that the electroweak symmetry
can be radiatively broken in our model. In the naturalness point of view, the
singlet scalar mass should be of ${\cal O}(1)\,{\rm TeV}$ or less. We also
consider right-handed neutrino extension of the model for neutrino mass
generation. The model does not affect the MPP scenario, and might keep the
naturalness with the new particle mass scale beyond TeV, thanks to accidental
cancellation of Higgs mass corrections.

DOI： 10.1093/ptep/ptw186

Other URL： http://arxiv.org/pdf/1608.00087v2

We study the vacuum stability and perturbativity conditions in the minimal
type-II seesaw model. These conditions give characteristic constraints to model
parameters. In the model, there is a $SU(2)_L$ triplet scalar field, which
could cause a large Higgs mass correction. From the naturalness point of view,
heavy Higgs masses should be lower than $350\,{\rm GeV}$, which can be testable
by the LHC Run-II results. Due to effects of the triplet scalar field,
branching ratios of the Higgs decay ($h\to \gamma \gamma, Z\gamma$) deviate
from the standard model, and large parameter region is excluded by the recent
ATLAS and CMS combined analysis of $h\to \gamma \gamma$. Our result of the
signal strength for $h\to \gamma \gamma$ is $R_{\gamma \gamma} \lesssim 1.1$,
but its deviation is too small to observe at the LHC experiment.

DOI： 10.1140/epjc/s10052-016-4180-z

Other URL： http://arxiv.org/pdf/1601.05217v2

We propose a new dynamics of the electroweak symmetry breaking in a
classically scale invariant version of the standard model. The scale invariance
is broken by the condensations of additional fermions under a strong coupling
dynamics. The electroweak symmetry breaking is triggered by negative mass
squared of the elementary Higgs doublet, which is dynamically generated through
the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field
interacting with additional fermions and Higgs doublet in order to avoid
massless Nambu-Goldstone bosons from the chiral symmetry breaking in a strong
coupling sector. We investigate the mass spectra and decay rates of these
pseudo-Nambu-Goldstone bosons, and show they can decay fast enough without
cosmological problems. We further evaluate the energy dependences of the
couplings between elementary fields perturbatively, and find that our model is
the first one which realizes the flatland scenario with the dimensional
transmutation by the strong coupling dynamics. Similarly to the conventional
flatland model with Coleman-Weinberg mechanism, the electroweak vacuum in our
model is meta-stable.

DOI： 10.1016/j.physletb.2016.02.052

Other URL： http://arxiv.org/pdf/1512.05061v1

There are a lot of works within a class of classically scale invariant model,
which is motivated by solving the gauge hierarchy problem. In this context, the
Higgs mass vanishes at the UV scale due to the classically scale invariance,
and is generated via the Coleman-Weinberg mechanism. Since the mass generation
should occur not so far from the electroweak scale, we extend the standard
model only around the TeV scale. We construct a model which can achieve the
gauge coupling unification at the UV scale. In the same way, the model can
realize the vacuum stability, smallness of active neutrino masses, baryon
asymmetry of the universe, and dark matter relic abundance. The model predicts
the existence vector-like fermions charged under $SU(3)_C$ with masses lower
than $1\,{\rm TeV}$, and the SM singlet Majorana dark matter with mass lower
than $2.6\,{\rm TeV}$.

DOI： 10.1007/JHEP02(2016)058

Other URL： http://arxiv.org/pdf/1511.02107v3

We suggest the so-called bosonic seesaw mechanism in the context of a
classically conformal $U(1)_{B-L}$ extension of the Standard Model with two
Higgs doublet fields. The $U(1)_{B-L}$ symmetry is radiatively broken via the
Coleman-Weinberg mechanism, which also generates the mass terms for the two
Higgs doublets through quartic Higgs couplings. Their masses are all positive
but, nevertheless, the electroweak symmetry breaking is realized by the bosonic
seesaw mechanism. Analyzing the renormalization group evolutions for all model
couplings, we find that a large hierarchy among the quartic Higgs couplings,
which is crucial for the bosonic seesaw mechanism to work, is dramatically
reduced toward high energies. Therefore, the bosonic seesaw is naturally
realized with only a mild hierarchy, if some fundamental theory, which provides
the origin of the classically conformal invariance, completes our model at some
high energy, for example, the Planck scale. We identify the regions of model
parameters which satisfy the perturbativity of the running couplings and the
electroweak vacuum stability as well as the naturalness of the electroweak
scale.

DOI： 10.1016/j.physletb.2016.01.050

Other URL： http://arxiv.org/pdf/1508.06828v2

We construct a model realizing the inverse seesaw mechanism. The model has
two types of gauge singlet fermions in addition to right-handed neutrinos. A
required Majorana mass scale (keV scale) for generating the light active
neutrino mass in the conventional inverse seesaw can be naturally explained by
a "seesaw" mechanism between the two singlet fermions in our model. We find
that our model can decrease the magnitude of hierarchy among the mass
parameters by $\mathcal{O}(10^4)$ from that in the conventional inverse seesaw
model. We also show that a successful resonant leptogenesis occurs for
generating the baryon asymmetry of the universe in our model. The desired mass
degeneracy for the resonant leptogenesis can also be achieved by the "seesaw"
between the two singlet fermions.

DOI： 10.1093/ptep/ptv149

Other URL： http://arxiv.org/pdf/1506.06946v3

We investigate the vacuum stability in a scale invariant local $U(1)_\chi$
model with vanishing scalar potential at the Planck scale. We find that it is
impossible to realize the Higgs mass of 125\,GeV while keeping the Higgs
quartic coupling $\lambda_H$ to be positive in all energy scale, that is the
same as the standard model. Once one allows $\lambda_H<0$, the lower bounds of
the $Z'$ boson mass are obtained through the positive definiteness of the
scalar mass squared eigenvalues, while the bounds are smaller than the LHC
bounds. On the other hand, the upper bounds strongly depend on the number of
relevant Majorana Yukawa couplings of the right-handed neutrinos $N_\nu$.
Considering decoupling effects of the $Z'$ boson and the right-handed
neutrinos, the condition of the singlet scalar quartic coupling
$\lambda_\phi>0$ gives the upper bound in $N_\nu=1$ case, while it does not
constrain $N_\nu=2$ and 3 cases. Especially, we find that $Z'$ boson mass is
tightly restricted for $N_\nu=1$ case as $M_{Z'} \lesssim 3.7\,{\rm TeV}$.

DOI： 10.1093/ptep/ptv121

Other URL： http://arxiv.org/pdf/1504.05669v2

We suggest a discriminant analysis of new physics beyond the standard model
through a detection of photon polarization in a radiative B meson decay. This
analysis is investigated in SUSY SU(5) GUT with right-handed neutrino and
left-right symmetric models. New physics search via CP asymmetry in the same
process are also evaluated in each model for comparison. We show that new
physics can be found via detecting the photon polarization in a parameter space
of TeV energy scale.

DOI： 10.1007/JHEP03(2015)160

Other URL： http://arxiv.org/pdf/1501.00668v3

DOI： 10.7566/JPSCP.8.023001

From the point of view of the gauge hierarchy problem, introducing an
intermediate scale in addition to TeV scale and the Planck scale ($M_{\rm Pl} =
2.4 \times 10^{18}\,{\rm GeV}$) is unfavorable. In that way, a gauge coupling
unification (GCU) is expected to be realized at $M_{\rm Pl}$. We explore
possibilities of GCU at $M_{\rm Pl}$ by adding a few extra particles with TeV
scale mass into the standard model (SM). When extra particles are fermions and
scalars (only fermions) with the same mass, the GCU at $M_{\rm Pl}$ can (not)
be realized. On the other hand, when extra fermions have different masses, the
GCU can be realized around $\sqrt{8 \pi} M_{\rm Pl}$ without extra scalars.
This simple SM extension has two advantages that a vacuum becomes stable up to
$M_{\rm Pl}$ ($\sqrt{8 \pi} M_{\rm Pl}$) and a proton lifetime becomes much
longer than an experimental bound.

DOI： 10.1016/j.nuclphysb.2015.09.004

Other URL： http://arxiv.org/pdf/1412.8230v3

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

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

CiNii Article

CiNii Article

CiNii Article

CiNii Article

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) x 10(2) GeV &lt;= m(S) &lt;= 1.4(1.2) x 10(3) GeV and 6.3(5.5) x 10(13) GeV &lt;= M-R &lt;= 1.6(1.2) x 10(14) 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 XENONIT.

DOI： 10.1103/PhysRevD.90.036006

DOI： 10.1103/PhysRevD.90.039905

We suggest a new model of 7 keV right-handed neutrino dark matter inspired by
a recent observation of 3.5 keV X-ray line signal in the XMM-Newton
observatory. It is difficult to derive the tiny masses with a suitable
left-right mixing of the neutrino in a framework of ordinary simple type-I
seesaw mechanism. We introduce a new Higgs boson, a dark matter-philic Higgs
boson, in which the smallness of its vacuum expectation value can be achieved.
We investigate suitable parameter regions where the observed dark matter
properties are satisfied. We find that the vacuum expectation value of dark
matter-philic Higgs boson should be about 0.17 GeV.

DOI： 10.1016/j.physletb.2015.02.014

Other URL： http://arxiv.org/pdf/1407.6827v3

We discuss the Higgs inflation scenario with singlet scalar dark matter and a right-handed neutrino. The singlet scalar and the right-handed neutrino play crucial roles for realizing a suitable plateau of Higgs potential with the center value of the top mass of Tevatron and LHC measurements. This Higgs inflation scenario predicts about a 1 TeV scalar dark matter and an O(10(14)) GeV right-handed neutrino by use of a 125.6 GeV Higgs mass, 173.34 GeV top mass, and a nonminimal gravity coupling xi similar or equal to 10.1. This inflation model is consistent with the recent result of the tensor-to-scalar ratio r = 0.20(-0.05)(+0.07) by the BICEP2 Collaboration.

DOI： 10.1103/PhysRevD.89.115009

We investigate the Higgs inflation and the Higgs portal dark matter with the
right-handed neutrino. The dark matter and the right-handed neutrino in the
Higgs inflation play important roles in explaining the recent experimental
results of the Higgs and top masses, and the cosmic microwave background by
BICEP2 at the same time. This inflation model predicts $805~{\rm GeV} \lesssim
m_{\rm DM} \lesssim1220~{\rm GeV}$ for the DM mass, $1.05 \times10^{14}~{\rm
GeV} \lesssim M_R \lesssim 2.04 \times10^{14}~{\rm GeV}$ for the right-handed
neutrino mass, and $8.42 \lesssim \xi \lesssim 12.4$ for the non-minimal
coupling within $m_H=125.6 \pm 0.35~{\rm GeV}$ for the Higgs and $M_t=173.34
\pm 0.76~{\rm GeV}$ for the top masses.

DOI： 10.1093/ptep/ptv053

Other URL： http://arxiv.org/pdf/1405.5738v3

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

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

We propose a new next-to-minimal supersymmetric standard model (NMSSM) which
is on a six-dimensional spacetime compactified on a $T^2/Z_3$ orbifold. In this
model, three gauge singlet fields $N, S_1$ and $S_2$ in addition to the minimal
supersymmetric standard model (MSSM) fields are introduced. These fields are
localized at some fixed points except for the singlet $N$ and the gauge fields.
The $\mu$ parameter is provided from the vacuum expectation value (vev) of $N$.
The $F$ terms get vevs simultaneously, and the gauginos mediate the
supersymmetry breaking to the MSSM sector. Both of these parameters are
strongly suppressed due to the profile of $N$. Thus these parameters induced
from those of the order of the so-called GUT scale can become close to the
electroweak scale without unnatural fine tuning.

DOI： 10.1093/ptep/ptu074

Other URL： http://arxiv.org/pdf/1401.2599v1

Higgs cubic coupling plays a crucial role in probing 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 nonperturbative Higgs model in which a runaway type of potential is used. In the model, the cross sections of pair production at the LHC are enlarged compared to the standard model. We also study the Higgs pair production induced by a noncanonical kinetic term of Higgs fields which will be important for searching the pair production at the ILC.

DOI： 10.1103/PhysRevD.89.015018

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

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

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

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

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

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

CiNii Article

We show renormalization group invariants in neutrino sector. These are found
from a simple analytical discussion of Majorana mass matrix for light
neutrinos. It is shown that the invariants are obtained by taking ratios among
elements of the Majorana neutrino mass matrix. The invariance is independent of
neutrino mass ordering and a parameterization of mixing matrix for the lepton
sector. Parameters in the runnings under renormalization group equations in the
neutrino sector are also analyzed.

DOI： 10.1007/JHEP08(2013)123

Other URL： http://arxiv.org/pdf/1306.1375v3

Under the assumption of hierarchical right-handed neutrino masses, masses of
right-handed neutrinos must be larger than $10^8$ GeV in the standard thermal
leptogenesis scenario, while the mass can be reduced to around 5 TeV in a
neutrinophilic two Higgs doublet model. On the other hand, resonant
leptogenesis can work with the masses of TeV-scale. However, necessary
degeneracy between the lightest and the second lightest right-handed neutrino
masses means unnatural fine-tuning of the order of $10^9$. In this paper, we
will investigate the resonant leptogenesis scenario in a neutrinophilic two
Higgs doublet model. We will find the mass can be reduced to 2 TeV and the
degeneracy becomes much milder as of the order of $10^4$. We will also show
that degenerate mass spectrum of active neutrinos is disfavored in this setup.

DOI： 10.1103/PhysRevD.87.123540

Other URL： http://arxiv.org/pdf/1305.2484v2

We investigate constraints on neutrino mass ordering and degeneracy by
considering the first cosmological result based on Planck measurements of the
cosmic microwave background. It is shown that the result at 95% CL rejects a
neutrino mass degeneracy larger than 85% (82.5%) for the normal (inverted)
hierarchical case. We can also find some regions where the neutrino mass
ordering will be able to be distinguished by combining a value of sum of the
neutrino masses with an effective neutrino mass determined by neutrino-less
double beta decay experiments.

DOI： 10.5506/APhysPolB.45.61

Other URL： http://arxiv.org/pdf/1305.0147v3

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

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

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

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

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

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

Among three typical energy scales, a neutrino mass scale (m(nu) similar to 0.1 eV), a grand unified theory (GUT) scale (M-GUT similar to 10(16) GeV), and a TeV scale (M-NP similar to 1 TeV), there is the 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" in this article. We investigate the phenomenology of the supersymmetry SU(5) GUT with neutrinophilic Higgs, where the above relation is realized dynamically when neutrinos are Dirac particles. As a remarkable feature of this model, accurate gauge coupling unification can be achieved in keeping with a proton stability. We also evaluate flavor changing processes in quark/lepton sectors.

DOI： 10.1103/PhysRevD.86.015019

An origin of flavor mixings in quark and lepton sectors is still a mystery,
and a structure of the flavor mixings in lepton sector seems completely
different from that of quark sector. In this letter, we point out that the
flavor mixing angles in quark and lepton sectors could be unified at a high
energy scale, when neutrinos are degenerate. It means that a minimal flavor
violation at a high energy scale can induce a rich variety of flavor mixings in
quark and lepton sectors at a low energy scale through quantum corrections.

DOI： 10.1209/0295-5075/100/31001

Other URL： http://arxiv.org/pdf/1206.2793v2

It is important to obtain effective operators by integrating out high energy degrees of freedom in physics. We suggest a general method of calculating accurate irrelevant operators in a scattering process without use of equation of motions. By using this method, for example, we will represent a complete set of dimension six operators in QCD, which are induced from physics beyond the standard model, supersymmetry and universal extra dimension. We will also show an example of effective anomalous 4-Fermi interactions induced from a little Higgs model.

DOI： 10.5506/APhysPolB.43.405

Parity violation in the QCD process is studied using helicity-dependent top-quark pair productions at the 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 a 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

DOI： 10.24532/soken.119.3_C13

CiNii Article

J-GLOBAL

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

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

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 in this letter. We suggest a simple
supersymmetric neutrinophilic Higgs doublet model, which realizes the above
relation dynamically as well as the suitable $m_\nu$ through a tiny vacuum
expectation value of neutrinophilic Higgs without additional scales other than
$M_{NP}$ and $M_{GUT}$. A gauge coupling unification, which is an excellent
feature in the supersymmetric standard model, is preserved automatically in
this setup.

DOI： 10.1209/0295-5075/96/21001

Other URL： http://arxiv.org/pdf/1107.4823v2

We propose a novel mechanism to generate a suitable baryon asymmetry from dark (hidden) sector. This is a Baryogenesis through a reverse pathway of the "asymmetric dark matter" scenario. In the mechanism, the asymmetry of dark matter is generated at first, and it is partially transferred into a baryon asymmetry in the standard model sector. This mechanism enables us not only to realize the generation of the baryon asymmetry but also to account for the correct amount of dark matter density in the present universe within a simple framework.

DOI： 10.1143/PTP.125.1311

We suggest new setup where SUSY breaking spurion F-term possesses lepton
number. This setup not only modifies sparticle mass spectra but also realizes
several new models, where neutrino mass is naturally induced through radiative
corrections. We here suggest two new models; the first one is (i):
pseudo-Dirac/Schizophrenic neutrino model, and the second one is (ii): pure
Majorana neutrino model. We will also show this setup can naturally apply to
the supersymmetric Zee-Babu model.

DOI： 10.1016/j.physletb.2011.05.050

Other URL： http://arxiv.org/pdf/1102.3472v1

It is well-known that leptogenesis in low energy scale is difficult in the
conventional Type-I seesaw mechanism with hierarchical right-handed neutrino
masses. We show that in a class of two Higgs doublet model, where one Higgs
doublet generates masses of quarks and charged leptons whereas the other Higgs
doublet with a tiny vacuum expectation value generates neutrino Dirac masses,
large Yukawa couplings lead to a large enough CP asymmetry of the right-handed
neutrino decay. Thermal leptogenesis suitably works at low energy scale as
keeping no enhancement of lepton number violating wash out effects. We will
also point out that thermal leptogenesis works well without confronting
gravitino problem in a supersymmetric neutrinophilic Higgs doublet model with
gravity mediated supersymmetry breaking. Neutralino dark matter and baryon
asymmetry generation by thermal leptogenesis are easily compatible in our
setup.

DOI： 10.1143/PTP.125.1155

Other URL： http://arxiv.org/pdf/1102.2889v1

We study implications of generalized non-zero Dirichlet boundary condition
along with the ordinary Neumann one on a bulk scalar in the Randall-Sundrum
warped compactification. First we show profiles of vacuum expectation value of
the scalar under the general boundary conditions. We also investigate
Goldberger-Wise mechanism in several setups with the general boundary
conditions of the bulk scalar field and find that the mechanism can work under
non-zero Dirichlet boundary conditions with appropriate vacuum expectation
values. Especially, we show that $SU(2)_R$ triplet Higgs in the bulk left-right
symmetric model with custodial symmetry can be identified with the
Goldberger-Wise scalar.

DOI： 10.1007/JHEP05(2011)125

Other URL： http://arxiv.org/pdf/1102.1970v2

The asymmetric dark matter scenario is known to give an interesting solution
for the cosmic coincidence problem between baryon and dark matter densities. In
the scenario, the dark matter asymmetry, which is translated to the dark matter
density in the present universe, is transferred from the B-L asymmetry
generated in the early universe. On the other hand, the generation of the B-L
asymmetry is simply assumed, though many mechanisms for the generation are
expected to be consistent with the scenario. We show that the generation of the
asymmetry in the sneutrino inflation scenario works similarly to the asymmetric
dark matter scenario, because the non-renormalizable operator which translates
the B-L asymmetry to the dark matter asymmetry is naturally obtained by
integrating right-handed neutrinos out. As a result, important issues
concerning cosmology (inflation, the mass density of dark matter, and the
baryon asymmetry of the universe) as well as neutrino masses and mixing have a
unified origin, namely, the right-handed neutrinos.

DOI： 10.1103/PhysRevD.84.055016

Other URL： http://arxiv.org/pdf/1101.5679v3

Publishing type：Internal/External technical report, pre-print, etc.  

Among three typical energy scales, a neutrino mass scale (m ν∼0.1 eV), a GUT scale (MGUT∼1016 GeV), and a TeV scale (MNP∼1 TeV), there is a fascinating relation, i.e.. The TeV scale, MNP, is a new physics scale beyond the standard model which is regarded as supersymmetry in this letter. We suggest a simple supersymmetric neutrinophilic Higgs doublet model, which realizes the above relation dynamically as well as the suitable mν through a tiny vacuum expectation value of the neutrinophilic Higgs doublet without additional scales other than MNP and MGUT. A gauge coupling unification, which is an excellent feature in the supersymmetric standard model, is preserved automatically in this setup. © Europhysics Letters Association 2011.

DOI： 10.1209/0295-5075/96/21001

DOI： 10.1007/JHEP11(2010)071

We suggest new simple model of generating tiny neutrino masses through a TeV-scale seesaw mechanism without requiring tiny Yukawa couplings. This model is a simple extension of the standard model by introducing extra one Higgs singlet, and one Higgs doublet with a tiny vacuum expectation value. Experimental constraints, electroweak precision data and no large flavor changing neutral currents, are satisfied since the extra doublet only has a Yukawa interaction with lepton doublets and right-handed neutrinos, and their masses are heavy of order a TeV-scale. Since active light neutrinos are Majorana particles, this model predicts a neutrinoless double beta decay.

DOI： 10.1140/epjc/s10052-010-1414-3

The positron anomaly recently reported by the cosmic-ray measurements can be
explained by the decaying dark matter scenario, where it decays mainly into
leptons with the lifetime of O(10^26) second. When the dark matter is a
fermionic particle, the lifetime of this order is known to be obtained by a
dimension 6 operator suppressed by the unification scale 10^16 GeV, while such
decay operators do not necessarily involve only leptons. In addition, the
scenario would be spoiled if there exist lower-dimensional operators inducing
the dark matter decay. We show in this letter that a single non-Abelian
discrete symmetry such as A_4 is possible to prohibit all such harmful
(non-leptonically coupled and lower-dimensional) operators. Moreover, the dark
matter decays into charged leptons in a flavor-blind fashion due to the
non-Abelian flavor symmetry, which results in perfect agreements not only with
the PAMELA data but also with the latest Fermi-LAT data reported very recently.
We also discuss some relevance between the discrete symmetry and neutrino
physics.

DOI： 10.1016/j.physletb.2010.11.063

Other URL： http://arxiv.org/pdf/1008.4777v1

We study the capability of the international linear collider (ILC) to probe
extra dimensions via the seesaw mechanism. In the scenario we study, heavy
Kaluza-Klein neutrinos generate tiny neutrino masses and, at the same time,
have sizable couplings to the standard-model particles. Consequently, a
Kaluza-Klein tower of heavy neutrinos (N) can be produced and studied at the
ILC through the process: e+e- -> vN followed by N -> Wl decay. We show that the
single lepton plus two-jets final states with large missing energy from this
signal process will provide a good opportunity to measure the masses and cross
sections of Kaluza-Klein neutrinos up to the third level. Furthermore, the
neutrino oscillation parameters can be extracted from the flavor dependence of
the lowest-mode signals, which give us information about the origin of
low-energy neutrino masses.

DOI： 10.1103/PhysRevD.82.093004

Other URL： http://arxiv.org/pdf/1008.2257v2

We suggest new simple model of generating tiny neutrino masses through a
TeV-scale seesaw mechanism without requiring tiny Yukawa couplings. This model
is a simple extension of the standard model by introducing extra one Higgs
singlet, and one Higgs doublet with a tiny vacuum expectation value.
Experimental constraints, electroweak precision data and no large flavor
changing neutral currents, are satisfied since the extra doublet only has a
Yukawa interaction with lepton doublets and right-handed neutrinos, and their
masses are heavy of order a TeV-scale. Since active light neutrinos are
Majorana particles, this model predicts a neutrinoless double beta decay.

DOI： 10.1140/epjc/s10052-010-1414-3

Other URL： http://arxiv.org/pdf/1005.1372v4

DOI： 10.1016/j.nuclphysb.2009.09.014

On an interval compactification in supersymmetric theory, boundary conditions
for bulk fields must be treated carefully. If they are taken arbitrarily
following the requirement that a theory is supersymmetric, the conditions could
give redundant constraints on the theory. We construct a supersymmetric action
integral on an interval by introducing brane interactions with which total
derivative terms under the supersymmetry transformation become zero due to a
cancellation. The variational principle leads equations of motion and also
boundary conditions for bulk fields, which determine boundary values of bulk
fields. By estimating mass spectrum, {\it spontaneous} supersymmetry breaking
in this simple setup can be realized in a new framework. This supersymmetry
breaking does not induce massless R-axion, which is favorable for
phenomenology. It is worth noting that fermions in hyper-multiplet, gauge
bosons, and the fifth-dimensional component of gauge bosons can have zero-modes
(while the other components are all massive as Kaluza-Klein modes), which fits
the gauge-Higgs unification scenarios.

DOI： 10.1103/PhysRevD.81.106005

Other URL： http://arxiv.org/pdf/0911.2557v3

We clarify and study our previous observation that, under a compactification
with boundaries or orbifolding, vacuum expectation value of a bulk scalar field
can have different extra-dimensional wave-function profile from that of the
lowest Kaluza-Klein mode of its quantum fluctuation, under presence of
boundary-localized potentials which would be necessarily generated through
renormalization group running. For concreteness, we analyze the Universal Extra
Dimension model compactified on orbifold $S^1/Z_2$, with brane-localized Higgs
potentials at the orbifold fixed points. We compute the Kaluza-Klein expansion
of the Higgs and gauge bosons in an $R_\xi$-like gauge by treating the
brane-localized potential as a small perturbation. We also check that the
$\rho$ parameter is not altered by the brane localized potential.

Other URL： http://arxiv.org/pdf/0910.4528v3

When the anti-periodic boundary condition is imposed for a bulk field in
extradimensional theories, independently of the background metric, the lightest
component in the anti-periodic field becomes stable and hence a good candidate
for the dark matter in the effective 4D theory due to the remaining accidental
discrete symmetry. Noting that in the gauge-Higgs unification scenario,
introduction of anti-periodic fermions is well-motivated by a phenomenological
reason, we investigate dark matter physics in the scenario. As an example, we
consider a five-dimensional SO(5)$\timesU(1)_X$ gauge-Higgs unification model
compactified on the $S^1/Z_2$ with the warped metric. Due to the structure of
the gauge-Higgs unification, interactions between the dark matter particle and
the Standard Model particles are largely controlled by the gauge symmetry, and
hence the model has a strong predictive power for the dark matter physics.
Evaluating the dark matter relic abundance, we identify a parameter region
consistent with the current observations. Furthermore, we calculate the elastic
scattering cross section between the dark matter particle and nucleon and find
that a part of the parameter region is already excluded by the current
experimental results for the direct dark matter search and most of the region
will be explored in future experiments.

DOI： 10.1007/JHEP03(2010)064

Other URL： http://arxiv.org/pdf/0910.3741v1

We propose a simple five-dimensional extension of the Standard Model (SM)
without any Higgs potential nor any extra fields. A Higgs doublet lives in the
bulk of a flat line segment and its boundary condition is Dirichlet at the ends
of the line, which causes the electroweak symmetry breaking without Higgs
potential. The vacuum expectation value of the Higgs is induced from the
Dirichlet boundary condition which is generally allowed in higher dimensional
theories. The lightest physical Higgs has non-flat profile in the extra
dimension even though the vacuum expectation value is flat. As a consequence,
we predict a maximal top Yukawa deviation (no coupling between top and Higgs)
for the Brane-Localized Fermion and a small deviation, a multiplication of
2\sqrt{2}/\pi\simeq0.9 to the Yukawa coupling, for the Bulk Fermion. The latter
is consistent with the electroweak precision data within 90% CL for
430GeV\lesssim m_{KK}\lesssim 500GeV.

DOI： 10.5506/APhysPolB.42.33

Other URL： http://arxiv.org/pdf/0910.3356v5

The scattering amplitude for the longitudinal weak bosons is investigated in
the SU(3) gauge-Higgs unification as a function of the scattering energy, the
Wilson line phase \theta_H and the warp factor. The \theta_H-dependence of the
amplitude is quite different in the flat and the warped spacetimes. Generically
the amplitude is enhanced for \theta_H=O(1) in the warped case while it is
almost independent of \theta_H in the flat case. This indicates the tree-level
unitarity is violated in the warped case at a lower scale than that in the flat
case.

DOI： 10.1088/1126-6708/2009/07/020

Other URL： http://arxiv.org/pdf/0904.3177v2

Publishing type：Internal/External technical report, pre-print, etc.  

We analyze a supersymmetry (SUSY) breaking model proposed by Intriligator, Seiberg and Shih in a supergravity (SUGRA) framework. This is a simple and natural setup which demands neither extra superpotential interactions nor an additional gauge symmetry. In the SUGRA setup, the U(1)R symmetry is explicitly broken by the constant term in the superpotential, and pseudo-{moduli} field naturally takes non-zero vacuum expectation value through a vanishing cosmological constant condition. Sfermions tend to be heavier than gauginos, and the strong-coupling scale is determined once a ratio of sfermion to gaugino masses is fixed.

DOI： 10.1088/1126-6708/2008/03/059

J-GLOBAL

J-GLOBAL

The gauge-Higgs unification is one of influential scenarios to solve the
hierarchy problem in the Standard Model. Recently, the scenario on the warped
background attracts many attentions due to a large possibility to construct a
realistic model naturally in this framework. It is, however, well known that
the effective potential for the Higgs field, which is the most important
prediction of the scenario, is not easy to calculate on the warped background,
because masses of Kaluza-Klein particles are not obtained analytically. In this
article, we derive useful formulae for the effective potential. The formulae
allow us to calculate the Higgs mass easily, thus to construct a realistic
model in the gauge-Higgs unification scenario on the warped background. Using
obtained formulae, we calculate contributions from bulk fermions with several
boundary conditions. We also show bulk fermions, which have boundary conditions
not allowed in the orbifold picture, do not contribute to the effective
potential.

DOI： 10.1143/PTP.120.77

Other URL： http://arxiv.org/pdf/0802.3431v1

We analyze a supersymmetry (SUSY) breaking model proposed by Intriligator,
Seiberg and Shih in a supergravity (SUGRA) framework. This is a simple and
natural setup which demands neither extra superpotential interactions nor an
additional gauge symmetry. In the SUGRA setup, the U(1)R symmetry is explicitly
broken by the constant term in the superpotential, and pseudo-moduli field
naturally takes non-zero vacuum expectation value through a vanishing
cosmological constant condition. Sfermions tend to be heavier than gauginos,
and the strong-coupling scale is determined once a ratio of sfermion to gaugino
masses is fixed.

DOI： 10.1088/1126-6708/2008/03/059

Other URL： http://arxiv.org/pdf/0802.1758v2

J-GLOBAL

We show the universal seesaw in the extra dimension setup, where three extra
vector-like fields exist in the 5D bulk with heavy masses. We take the
framework of the left-right symmetric model. The universal seesaw formula is
easily obtained as a replacement of the vector-like mass in 4D case M_i to
2 M_* tan[pi RM_i] (M_*: 5D Planck scale,
M_i: vector-like bulk mass, and
R: compactification radius). The smallness of Dirac neutrino mass can be
naturally explained in the 5D setup. We also show the Majorana neutrino case.

DOI： 10.1103/PhysRevD.74.113002

Other URL： http://arxiv.org/pdf/hep-ph/0608257v1

Publishing type：Internal/External technical report, pre-print, etc.  

In the 5D theory in which only 3 generation right-handed neutrinos are in the<br />
bulk, the neutrino flavor mixings and the mass spectrum can be constructed<br />
through the seesaw mechanism. The 5D seesaw is easily calculated just by a<br />
replacement of the<br />
Majorana mass eigenvalues, M_i, by 2 M_*tan(h)[\pi RM_i] (M_*: 5D Planck<br />
scale,<br />
R: compactification radius). The 5D features appear when the bulk mass, which<br />
induces the 4D Majorana mass, is the same as the compactification scale or<br />
larger than it. Depending on the type of bulk mass, the seesaw scales of the 3<br />
generations are strongly split (the ...

DOI： 10.1088/1126-6708/2006/05/030

In the 5D theory in which only 3 generation right-handed neutrinos are in the
bulk, the neutrino flavor mixings and the mass spectrum can be constructed
through the seesaw mechanism. The 5D seesaw is easily calculated just by a
replacement of the
Majorana mass eigenvalues, M_i, by 2 M_*tan(h)[\pi RM_i] (M_*: 5D Planck
scale,
R: compactification radius). The 5D features appear when the bulk mass, which
induces the 4D Majorana mass, is the same as the compactification scale or
larger than it. Depending on the type of bulk mass, the seesaw scales of the 3
generations are strongly split (the tan-function case) or degenerate (the
tanh-function case). In the split case, the seesaw enhancement is naturally
realized. The single right-handed neutrino dominance works in a simple setup,
and some specific mass textures, which are just assumptions in the 4D setup,
can be naturally obtained in
5 dimensions. The degenerate case is also useful for a suitable neutrino
flavor structure.

DOI： 10.1088/1126-6708/2006/05/030

Other URL： http://arxiv.org/pdf/hep-ph/0603119v3

Publishing type：Internal/External technical report, pre-print, etc.  

We show a universal seesaw mechanism in the extra dimension theory. We take a left-right symmetric model in which extra three vectorlike fields exist in the 5D bulk. The universal seesaw formula is easily obtained as a replacement of the vectorlike mass in the 4D case Mi to 2M*tan[πRMi] (M*: 5D Planck scale, Mi: vectorlike bulk mass, and R: compactification radius). The smallness of Dirac neutrino mass can be naturally explained in the 5D setup. We also show the Majorana neutrino case. © 2006 The American Physical Society.

DOI： 10.1103/PhysRevD.74.113002

Discrete flavor symmetry is explored for an intrinsic property of mass matrix
forms of quarks and leptons. In this paper we investigate the S3 permutation
symmetry and derive the general forms of mass matrices in various types of S3
theories. We also exhibit particular realizations of previous ansatze of mass
matrices, which have often been applied in the literature to the standard model
Yukawa sector. Discrete flavor symmetry is also advantageous for vanishing
matrix elements being dynamically generated in the vacuum of scalar potential.
This is due to the fact that group operations are discrete. While zero elements
themselves do not explain mass hierarchies, we introduce an abelian flavor
symmetry. A non-trivial issue is whether successful quantum numbers can be
assigned so that they are compatible with other (non-abelian) flavor
symmetries. We show typical examples of charge assignments which not only
produce hierarchical orders of mass eigenvalues but also prohibit
non-renormalizable operators which disturb the hierarchies in first-order
estimation. As an explicit application, a flavor model is constructed in grand
unification scheme with S3 and U(1) (or Z_N) flavor symmetries.

DOI： 10.1016/j.nuclphysb.2006.01.027

Other URL： http://arxiv.org/pdf/hep-ph/0511108v2

We derive the low energy effective theory of Gauge-Higgs unification (GHU)
models in the usual four dimensional framework. We find that the theories are
described by only the zero-modes with a particular renormalization condition in
which essential informations about GHU models are included. We call this
condition ``Gauge-Higgs condition'' in this letter. In other wards, we can
describe the low energy theory as the SM with this condition if GHU is a model
as the UV completion of the Standard Model. This approach will be a powerful
tool to construct realistic models for GHU and to investigate their low energy
phenomena.

DOI： 10.1088/1126-6708/2006/02/073

Other URL： http://arxiv.org/pdf/hep-ph/0511046v2

DOI： 10.24532/soken.111.3_C26

CiNii Article

J-GLOBAL

The gauge-Higgs unification theory identifies the zero mode of the extra
dimensional component of the gauge field as the usual Higgs doublet. Since this
degree of freedom is the Wilson line phase, the Higgs does not have the mass
term nor quartic coupling at the tree level. Through quantum corrections, the
Higgs can take a vacuum expectation value, and its mass is induced. The
radiatively induced mass tends to be small, although it can be lifted to
${\mathcal O}(100)$ GeV by introducing the ${\mathcal O}(10)$ numbers of bulk
fields. Perturbation theory becomes unreliable when a large number of bulk
fields are introduced. We reanalyze the Higgs mass based on useful expansion
formulae for the effective potential and find that even a small number of bulk
field can have the suitable heavy Higgs mass. We show that a small (large)
number of bulk fields are enough (needed) when the SUSY breaking mass is large
(small). We also study the case of introducing the soft SUSY breaking scalar
masses in addition to the Scherk-Schwarz SUSY breaking and obtain the heavy
Higgs mass due to the effect of the scalar mass.

DOI： 10.1016/j.physletb.2005.04.027

Other URL： http://arxiv.org/pdf/hep-ph/0411250v2

We study gauge symmetry breaking patterns in supersymmetric gauge models
defined on $M^4\times S^1$. Instead of utilizing the Scherk-Schwarz mechanism,
supersymmetry is broken by bare mass terms for gaugino and squarks. Though the
matter content is the same, depending on the magnitude of the bare mass, the
gauge symmetry breaking patterns are different. We present two examples, in one
of which the partial gauge symmetry breaking $SU(3)\to SU(2)\times U(1)$ is
realized.

DOI： 10.1016/j.physletb.2004.11.039

Other URL： http://arxiv.org/pdf/hep-th/0410244v2

We propose a simple superpotential for the Higgs doublets, where the
electroweak symmetry is broken at the supersymmetric level. We show that, for a
class of supersymmetry breaking scenarios, the electroweak scale can be stable
even though the supersymmetry breaking scale is much higher than it. Therefore,
all the superpartners and the Higgs bosons can be decoupled from the
electroweak scale, nevertheless no fine-tuning is needed. We present a concrete
model, as an existence proof of such a model, which generates the
superpotential dynamically. According to supersymmetry breaking scenarios to be
concerned, various phenomenological applications of our model are possible. For
example, based on our model, the recently proposed ``split supersymmetry''
scenario can be realized without fine-tuning. If the electroweak scale
supersymmetry breaking is taken into account, our model provides a similar
structure to the recently proposed ``fat Higgs'' model and the upper bound on
the lightest Higgs boson mass can be relaxed.

CiNii Article

Other URL： http://arxiv.org/pdf/hep-ph/0409113v2

CiNii Article

We study the vacuum structure in 5D SO(10) grand unified theory (GUT)
compactified on $S^1/Z_2$ orbifold, where SO(10) is broken into $SU(3)\times
SU(2)\times U(1)^2$ through the boundary conditions. Although a lot of people
extended to 6D to avoid massless colored particle, we can show they obtain
finite masses by the radiative corrections. In a supersymmetric case, the
fermionic partner of the zero-mode can also acquire non-vanishing mass through
the SUSY breaking effects, and the gauge coupling unification can be recovered
by use of brane localized kinetic terms.

DOI： 10.1016/j.physletb.2004.07.015

Other URL： http://arxiv.org/pdf/hep-ph/0403264v1

DOI： 10.1103/PhysRevD.69.059902

We study the dynamical symmetry breaking in the gauge-Higgs unification of
the 5D theory compactified on an orbifold, $S^1/Z_2$. This theory identifies
Wilson line degrees of freedoms as ``Higgs doublets''. We consider $SU(3)_c
\times SU(3)_W$ and SU(6) models with the compactification scale of order a few
TeV. The gauge symmetries are reduced to $SU(3)_c \times SU(2)_L \times U(1)_Y$
and $SU(3)_c \times SU(2)_L \times U(1)_Y \times U(1)$, respectively, through
the orbifolding boundary conditions. We estimate the one loop effective
potential of ``Higgs doublets'', and find that the electro-weak breaking is
realized through the radiative corrections when there are suitable numbers of
bulk fields possessing the suitable representations. The masses of ``Higgs
doublets'' are ${\mathcal O}(100)$ GeV in this scenario.

DOI： 10.1103/PhysRevD.70.015010

Other URL： http://arxiv.org/pdf/hep-ph/0401183v2

DOI： 10.24532/soken.107.3_C93

CiNii Article

J-GLOBAL

CiNii Article

CiNii Article

DOI： 10.24532/soken.104.4_D46

J-GLOBAL

CiNii Article

Publishing type：Internal/External technical report, pre-print, etc.  

We suggest two grand unified models where the fifth dimensional coordinate is<br />
compactified on an $S_1/(Z_2 \times Z_2&#039;)$ orbifold.

We suggest two grand unified models where the fifth dimensional coordinate is
compactified on an $S_1/(Z_2 \times Z_2')$ orbifold.

Other URL： http://arxiv.org/pdf/hep-ph/0110164v1

The quantum effects of lepton flavor mixing angles can be easily estimated by using the technique in Ref.[1]. The cases of hierarchical or the opposite signs between the generations guarantee stable mixing angles against quantum corrections. We also show that physical Majorana phases connect the &quot;stable&quot; region with the &quot;unstable&quot; region.

DOI： 10.24532/soken.102.6_F142

CiNii Article

CiNii Article

My talk is concentrating on the quantum effects on neutrino mass and lepton
flavor mixing matrices in the framework of the minimal supersymmetric standard
model with the effective dimension-five operator which gives the Majorana
masses of neutrinos.

Other URL： http://arxiv.org/pdf/hep-ph/0010179v1

Publishing type：Internal/External technical report, pre-print, etc.  

My talk is concentrating on the quantum effects on neutrino mass and lepton<br />
flavor mixing matrices in the framework of the minimal supersymmetric standard<br />
model with the effective dimension-five operator which gives the Majorana<br />
masses of neutrinos.

DOI： 10.24532/soken.102.6_F142

CiNii Article

CiNii Article

DOI： 10.1016/S0370-2693(00)00275-6

CiNii Article

CiNii Article

J-GLOBAL

DOI： 10.24532/soken.98.5_E129

CiNii Article

We suggest a simple composite model that induces the large flavor mixing of a neutrino in the supersymmetric theory. This model has only one hyper-color in addition to the standard gauge group, which makes composite states of preens. In this model, the 10 and 1 representations in SU(5) grand unified theory are composite states and produce the mass hierarchy. This explains why large mixing is realized in the lepton sector, while small mixing is realized in the quark sector. This model can naturally solve the atmospheric neutrino problem. We can also serve the solar neutrino problem by improving the model. [S0556-2821(99)07401-9].

Publishing type：Internal/External technical report, pre-print, etc.  

We suggest a simple composite model that induces the large flavor mixing of a neutrino in the supersymmetric theory. This model has only one hyper-color in addition to the standard gauge group, which makes composite states of preons. In this model, the 10 and 1 representations in SU(5) grand unified theory are composite states and produce the mass hierarchy. This explains why large mixing is realized in the lepton sector, while small mixing is realized in the quark sector. This model can naturally solve the atmospheric neutrino problem. We can also solve the solar neutrino problem by improving the model. © 1999 The American Physical Society.

DOI： 10.1103/PhysRevD.59.035011

J-GLOBAL

CiNii Article

We suggest a simple composite model that induces the large flavor mixing of
neutrino in the supersymmetric theory. This model has only one hyper-color in
addition to the standard gauge group, which makes composite states of preons.
In this model, {\bf 10} and {\bf 1} representations in SU(5) grand unified
theory are composite states and produce the mass hierarchy. This explains why
the large mixing is realized in the lepton sector, while the small mixing is
realized in the quark sector. This model can naturally solve the atmospheric
neutrino problem. We can also solve the solar neutrino problem by improving the
model.

DOI： 10.1103/PhysRevD.59.035011

Other URL： http://arxiv.org/pdf/hep-ph/9807552v1

DOI： 10.24532/soken.97.4_D12

CiNii Article

DOI： 10.24532/soken.97.4_D12

J-GLOBAL

There are experimental indications of large flavor mixing between nu(mu) and nu(tau). In the unification models, in which the massless sector includes extra particles beyond the standard model, there possibly appear mixings between quarks (leptons) and extra particles. When large mixings occur, lepton flavor mixings can be quite different from quark flavor mixings. By studying the string inspired SU(6) x SU(2)(R) model with global flavor symmetries, we obtain the neutrino flavor mixing sin theta(23) similar or equal to lambda = sin theta(C) up to renormalization effects. It can be expected that due to large Yukawa couplings of the third generation, the renormalization effect increases sin2 theta(23) naturally up to similar to 1 at the electroweak scale. The fermion mass spectra and the CKM matrix of quarks obtained in this paper are also phenomenologically viable.

DOI： 10.1143/PTP.99.831

CiNii Article

CiNii Article

We present a composite model that is based on nonperturbative effects of N = 1 supersymmetric SU(N-C) gauge theory with N-f = N-C + 1 flavors. In this letter, we consider N-C = 7, where all fields of one generation (quarks, leptons and Higgs) are bound states of preens and anti-preens. When SU(7)(H) coupling becomes strong, Yukawa couplings of quarks and leptons are generated dynamically. We show the one-generation model first and then we try to extend it to the three-generation model.

DOI： 10.1142/S0217732398000826

We propose a method to examine the T/CP invariance of the heaviest lepton, tau, by means of a triple-momentum correlation for the reaction e(+)e(-) --&gt; tau(+)tau(-), tau --&gt; e/&lt;mu nu(nu)over bar&gt; during the course of the B-Factory experimental program. An unprecedented high sensitivity could be obtained without requiring a high integrated luminosity.

DOI： 10.1143/PTP.99.413

CiNii Article

In N=1 Supersymmetric gauge theories, we can calculate non-perturbative
effects in the superpotential. It is interesting to apply this effect to the
phenomenology. We show two models here. One is the low energy supersymmetry
(SUSY) breaking scenario without messenger sector, and the second is the
composite model generating Yukawa interaction dynamically.

Other URL： http://arxiv.org/pdf/hep-ph/9712403v1

Publishing type：Internal/External technical report, pre-print, etc.  

In N=1 Supersymmetric gauge theories, we can calculate non-perturbative<br />
effects in the superpotential. It is interesting to apply this effect to the<br />
phenomenology. We show two models here. One is the low energy supersymmetry<br />
(SUSY) breaking scenario without messenger sector, and the second is the<br />
composite model generating Yukawa interaction dynamically.

We propose a simple gauge-mediated supersymmetry breaking model in which suitable soft breaking masses are dynamically generated without relying on the messenger gauge interaction. This model is constructed as an extention of the 3-2 model and needs no fine-tuning of parameters. The dynamical supersymmetry breaking sector contains nonrenormalizable interactions and vectorlike fields. Nonrenormalizable terms are characterized by the couplings of 0(1) in units of the Planck scale. The hierarchy of various mass scales in the model arises from the nonrenormalizable terms. The vacuum of this model conserves the color and electroweak symmetry. We also discuss a possible solution to the mu problem in this framework.

DOI： 10.1103/PhysRevD.56.4207

CiNii Article

CiNii Article

CiNii Article

Venue：大阪公立大学  

Venue：オンライン開催  

Venue：オンライン開催  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (general)  

SDGs：

Type：Lecture

Number of participants：120（人）

SDGs：

Type：Seminar, workshop

Number of participants：50（人）

SDGs：

Type：Seminar, workshop

Number of participants：50（人）

SDGs：

Type：Seminar, workshop

Number of participants：50（人）

SDGs：

Type：Seminar, workshop

Number of participants：50（人）

Type：Seminar, workshop

Number of participants：50（人）

SDGs：

Type：Seminar, workshop

Number of participants：50（人）

SDGs：

Type：Visiting lecture

Number of participants：100（人）

SDGs：

Type：Visiting lecture

Number of participants：100（人）

Audience：High school students

物理は面白いでしょうか?暗記科目だと思っていませんか?苦手意識があるかもしれません。 公式の奥の本質を知るととても面白く美しい世界がひらけてきます。周期表や屈折率について、 その奥にある本質の世界に皆さんを招待します。
令和4年 7月14日木 10:40-11:30　大阪教育大学付属高等学校平野校舎