152 citations · 1.9k across the 51 of their papers we have counts for
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Supersymmetric Baryogenesis in a Hybrid Inflation Model
Yoshihiro Gunji, Koji Ishiwata, Takahiro Yoshida
We study baryogenesis in a hybrid inflation model which is embedded to the minimal supersymmetric model with right-handed neutrinos. Inflation is induced by a linear combination of…
Subcritical regime of hybrid inflation with modular symmetry
Yoshihiro Gunji, Koji Ishiwata, Takahiro Yoshida
We consider a supergravity model that has the modular symmetry and discuss the interplay between the neutrino mixing and inflation. The model contains right-handed neutrinos…
Topology-insensitive axion mass in magnetic topological insulators
Koji Ishiwata
We study the axion in three-dimensional topological insulators with magnetic impurities under finite temperature. We find a stable antiferromagnetic ground state and ferromagnetic…
Axion-Gauge Field Dynamics with Backreaction
Koji Ishiwata, Eiichiro Komatsu, Ippei Obata
Phenomenological success of inflation models with axion and SU(2) gauge fields relies crucially on control of backreaction from particle production. Most of the previous study only…
Subcritical hybrid inflation in a generalized superconformal model
Yoshihiro Gunji, Koji Ishiwata
We study a generalized superconformal model that gives rise to a subcritical regime of -term hybrid inflation. Exhibiting the model both in a Jordan frame and in the Einstein fr…
Axion mass in antiferromagnetic insulators
Koji Ishiwata
We calculate axion potential in antiferromagnetic insulators from path integral. It is derived from the effective potential for the order parameter of the antiferromagnetic phase i…
Leptogenesis after superconformal subcritical hybrid inflation
Yoshihiro Gunji, Koji Ishiwata
We consider an extended version of superconformal subcritical hybrid inflation model by introducing three right-handed neutrinos that have the Majorana mass terms. In the model one…
Probing pseudo Nambu-Goldstone boson dark matter at loop level
Koji Ishiwata, Takashi Toma
In the standard model extended by a single complex scalar boson with a softly broken global U(1) symmetry, a pseudo Nambu-Goldstone boson becomes a candidate for dark matter. In th…
Longitudinal W boson scattering in a light scalar top scenario
Koji Ishiwata, Yuki Yonekura
Scalar tops in the supersymmetric model affect the potential of the standard model-like Higgs at the quatum level. In light of the equivalence theorem, the deviation of the potenti…
Constraining particle dark matter using local galaxy distribution
Shin'ichiro Ando, Koji Ishiwata
It has been long discussed that cosmic rays may contain signals of dark matter. In the last couple of years an anomaly of cosmic-ray positrons has drawn a lot of attentions, and re…
scattering in a radiative electroweak symmetry breaking scenario
Kazuhiro Endo, Koji Ishiwata, Yukinari Sumino
A classically scale invariant (CSI) extension of the standard model (SM) induces radiative electroweak symmetry breaking and predicts anomalously large Higgs self-interactions. Hen…
Direct detection of singlet dark matter in classically scale-invariant standard model
Kazuhiro Endo, Koji Ishiwata
Classical scale invariance is one of the possible solutions to explain the origin of the electroweak scale. The simplest extension is the classically scale-invariant standard model…
New Vector-Like Fermions and Flavor Physics
Koji Ishiwata, Zoltan Ligeti, Mark B. Wise
We study renormalizable extensions of the standard model that contain vector-like fermions in a (single) complex representation of the standard model gauge group. There are 11 mode…
QCD Effects on Direct Detection of Wino Dark Matter
Junji Hisano, Koji Ishiwata, Natsumi Nagata
We complete the calculation of the wino-nucleon scattering cross section up to the next-to-leading order in . We assume that the other sparticles are decoupled and wino intera…
Grand Unification and Subcritical Hybrid Inflation
Wilfried Buchmuller, Koji Ishiwata
We consider hybrid inflation for small couplings of the inflaton to matter such that the critical value of the inflaton field exceeds the Planck mass. It has recently been shown th…
Axino Dark Matter in Moduli-induced Baryogenesis
Koji Ishiwata
We consider axino dark matter in large R-parity violation (RPV). In moduli-dominated universe, axino is produced thermally or non-thermally via saxion decay, then late-decaying mod…
Moduli-induced Baryogenesis
Koji Ishiwata, Kwang Sik Jeong, Fuminobu Takahashi
We study a scenario for baryogenesis in modular cosmology and discuss its implications for the moduli stabilization mechanism and the supersymmetry (SUSY) breaking scale. If moduli…
Phenomenology of heavy vector-like leptons
Koji Ishiwata, Mark B. Wise
We study the impact that a heavy generation of vector-like leptons can have on the value of the electric dipole moment of the electron, and the rates for the flavor violating proce…
Baryogenesis with Higher Dimension Operators
Clifford Cheung, Koji Ishiwata
We propose a simple model of baryogenesis comprised of the standard model coupled to a singlet X via higher dimension operators O. In the early universe, X is thermalized by O medi…
Direct Search of Dark Matter in High-Scale Supersymmetry
Junji Hisano, Koji Ishiwata, Natsumi Nagata
We study direct detection of dark matter in supersymmetric (SUSY) model where most of SUSY particles have very high-scale masses beyond the weak scale. In the scenario, Wino-like o…
Dark Matter in Classically Scale-Invariant Two Singlets Standard Model
Koji Ishiwata
We consider a model where two new scalars are introduced in the standard model, assuming classical scale invariance. In this model the scale invariance is broken by quantum correct…
Natural Supersymmetry and b -> s gamma constraints
Koji Ishiwata, Natsumi Nagata, Norimi Yokozaki
We investigate constraints from the observed branching ratio for b -> s gamma and fine-tuning in the framework of natural supersymmetry. The natural supersymmetry requires the larg…
Direct Detection of Dark Matter Degenerate with Colored Particles in Mass
Junji Hisano, Koji Ishiwata, Natsumi Nagata
In this Letter we explore the direct detection of the dark matter in the universe, assuming the dark matter particles are degenerate in mass with new colored particles below TeV sc…
Higgs Properties and Fourth Generation Leptons
Koji Ishiwata, Mark B. Wise
It is possible that there are additional vector-like generations where the quarks have mass terms that do not originate from weak symmetry breaking, but the leptons only get mass t…