arXiv subjects

Tetsuo Shindou

Publications and source records attributed to Tetsuo Shindou.

At least 19 recordsLinked to original sources

arXiv2025

Classification of Higgs sectors from group theoretical properties of UV gauge theories

Extended Higgs sectors are often introduced to explain phenomena beyond the standard model (BSM). The existence of multiple scalar fields may cause the Landau pole below the Planck scale. In this case, the low-energy theory may be replaced by an asymptotic-free gauge theory. In this paper, we consider an $\mathrm{SU}(2)$ gauge theory with confinement as such an ultraviolet theory of the extended Higgs sectors. We investigate the relation between scalar particle contents at the low energy and group theoretical properties of fundamental fermions of the gauge theory. We find that particle contents of various extended Higgs sectors previously proposed to explain the BSM problems are deduced by each charge assignment of flavor symmetry of the fundamental fermions of the $\mathrm{SU}(2)$ gauge symmetry. Our findings may provide a new picture for the ultraviolet completion of the extended Higgs sectors.

hep-ph↗

arXiv2025

Renormalization Group Running of the Minimal Leptophilic Dark Matter Model toward a UV Completion

We study the renormalization group running of the coupling constants in a minimal leptophilic dark matter model in which a Standard Model singlet fermion, acting as the dark matter (DM) candidate, couples exclusively to right-handed charged leptons via a new charged scalar mediator. Reproduction of the observed thermal relic abundance of the DM candidate requires sizable Yukawa couplings, and such sizable Yukawa couplings can significantly affect the renormalization group evolution of the model parameters. We examine the conditions that the model remains perturbative and the vacuum stability is maintained up to high-energy scales. We find that the parameter space is severely constrained to ensure the perturbativity and the vacuum stability up to the Planck scale. In particular, the masses of the dark matter and the charged scalar mediator should be smaller than about 350 GeV and can be tested by future collider experiments. The lower bound of the dark matter mass that is larger than a few GeV is also obtained by perturbativity.

hep-ph↗

arXiv2024

On the CP Properties of Spin-0 Dark Matter

Aiming to uncover the CP properties of spin-0 particle Dark Matter (DM), we explore a two-component DM scenario within the framework of 3-Higgs Doublet Models (3HDMs), a well-motivated set-up previously studied due to the complementarity of its collider and astrophysical probes. We devise benchmark points in which the two components of DM have same CP in one case and opposite CP in another. We then show several cross section distributions of observables at collider experiments where the two cases are clearly distinguishable.

hep-ph↗

arXiv2023

12CO and 13CO observation of the low-metallicity dwarf galaxy DDO 154

The conversion factor from carbon monoxide (CO) intensity to molecular gas mass is a source of large uncertainty in understanding gas and its relation to star formation in galaxies. In particular, the conversion factor in low metallicity environments have remained elusive, as currently only two galaxies have been detected in any CO isotopes in environments with 12+log (O/H) < 8.0. Here we report 12CO(J=1-0) and 13CO(J=1-0) observations towards a star forming region in DDO 154, a low metallicity dwarf irregular galaxy at 12+log (O/H) = 7.67. This is a re-observation of a previous non-detection at higher angular and velocity resolution. No significant emission was detected. By estimating the molecular gas mass from associated star formation, we find that DDO 154 has a conversion factor of more than 10^3 times the Milky Way. Alternatively, if we estimate molecular mass using dust continuum emission, the conversion factor is at least 2 orders of magnitude larger than the Milky Way. These estimates signify a large amount of CO-dark molecular gas in this galaxy.

astro-ph.GA↗

arXiv2023

Flavor physics in SU(5) GUT with scalar fields in the 45 representation

We study a realistic SU(5) grand unified model, where a 45 representation of scalar fields is added to the Georgi-Glashow model in order to realize the gauge coupling unification and the masses and mixing of quarks and leptons. The gauge coupling unification together with constraints from proton decay implies mass splittings in scalar representations. We assume that an SU(2) triplet component of the 45 scalar, which is called $S_3$ leptoquark, has a TeV-scale mass, and color-sextet and color-octet ones have masses of the order of $10^6$ GeV. We calculate one-loop beta functions for Yukawa couplings in the model, and derive the low-energy values of the $S_3$ Yukawa couplings which are consistent with the grand unification. We provide predictions for lepton-flavor violation and lepton-flavor-universality violation induced by the $S_3$ leptoquark, and find that current and future experiments have a chance to find a footprint of our SU(5) model.

hep-ph↗

arXiv2022

Low-scale leptogenesis and dark matter in a three-loop radiative seesaw model

We show that three open questions in particle physics and cosmology: the origin of neutrino mass, the identity of dark matter, and the origin of the baryon asymmetry of the universe can be explained simultaneously in the three-loop seesaw model proposed by Krauss, Nasri, and Trodden. We discuss the difficulty of successful leptogenesis with three right-handed neutrinos, and we propose a scenario with four right-handed neutrinos that satisfies all observational constraints. This scenario predicts a sleptonlike particle as light as a few hundreds GeV that can be probed by future collider experiments.

hep-ph↗

arXiv2022

Lower bounds on lepton flavor violating branching ratios in a radiative seesaw model

We study the lepton flavor violating decays such as $μ\to eγ$, $τ\to eγ$, $τ\to μγ$ in the three-loop radiative seesaw model proposed by Krauss, Nasri, and Trodden. In this model, the relevant coupling constants are larger for the heavier scalars that run inside loop diagrams to generate the appropriate magnitude of neutrino masses. Imposing a criterion that all the coupling constants must be small enough to be treated perturbatively, we find an upper bound on the mass of one of the scalars. By combining it with neutrino mass parameters, we derive lower bounds on the branching ratios of the lepton flavor violating processes. In a case with the inverted mass ordering and best-fit neutrino oscillation parameters, one of the lower bounds is $\text{Br}(μ\to eγ)>1.1\times 10^{-13}$, which is within the reach of the MEG~II experiment.

hep-ph↗

arXiv2022

CP-Violation in the 3-Higgs Doublet Model: CP-Asymmetries from Charged Higgs Bosons and Electric Dipole Moments

We propose a CP-violating source in the charged Higgs sector of a 3-Higgs Doublet Model (3HDM) that will contribute to three CP-asymmetry observables for low energy processes. In the context of such a 3HDM, a measurement of one of the specific asymmetry observables (i.e., $\bar{B} \to X_{s+d} γ$) could obtain up to 2.5% or more, which would give a 5$σ$ evidence for physics Beyond the SM (BSM) from the full BELLE II data set. In addition to these CP-violating observables, the current measurements of Electron Dipole Moments (EDMs) constrain the available parameter region of the CP-violating 3HDM. In this work, we perform a thorough analysis of the parameter space of it to find the regions that satisfy EDMs, $\bar{B} \to X_s γ$, direct collider searches for charged Higgs bosons as well as theoretical bounds.

hep-ph↗

arXiv2021

Lepton Flavour Violation in a radiative neutrino mass model with the asymmetric Yukawa structure

Though models with the radiative neutrino mass generation are phenomenologically attractive, the complicated relationship between the flavour structure of additional Yukawa matrices and the neutrino mass matrix sometimes is a barrier to explore the models. We introduce a simple prescription to analyze the relation in a class of models with the asymmetric Yukawa structure. We then apply the treatment to the Zee-Babu model as a concrete example of the class and discuss the phenomenological consequences of the model. The combined studies among the neutrino physics, the lepton flavour violation, and the search for the new particles at the collider experiments provide the anatomy of the Zee-Babu model.

hep-ph↗

arXiv2020

CP asymmetries of ${\overline B}\to X_s/X_dγ$ in models with three Higgs doublets

Direct CP asymmetries (${\cal A}_{CP}$) in the inclusive decays of ${\overline B}\to X_sγ$ and ${\overline B}\to X_{s+d}γ$ of the order of $1\%$ will be probed at the BELLE II experiment. In this work, three such asymmetries are studied in the context of a three-Higgs-doublet model (3HDM), and it is shown that all three ${\cal A}_{CP}$ can be as large as the current experimental limits. Of particular interest is ${\cal A}_{CP}$ for ${\overline B}\to X_{s+d}γ$, which is predicted to be effectively zero in the Standard Model (SM). A measurement of $2.5\%$ or more for this observable with the full BELLE II data would give $5σ$ evidence for physics beyond the SM. We display parameter space in the 3HDM for which such a clear signal is possible.

hep-ph↗

arXiv2018

Electric dipole moments and dark matter in a CP violating MSSM

We investigate electric dipole moments (EDMs) in a CP-violating minimal supersymmetric standard model with the Bino-like neutralino dark matter (DM) annihilating through the heavy Higgs funnel. Motivated by the current experimental results, in particular, the measured mass of the standard model-like Higgs boson, we consider a mass spectrum with stop masses of about 10 TeV. For the other sfermions, we consider masses of about 100 TeV. We show that CP-violating phases of the order of ten degrees in gaugino and Higgsino mass parameters are consistent with the current bound by EDMs of the electron, the neutron, and the mercury. They are within the reach of future experiments. We also show that effects of CP-violating phases induce a difference in DM-nucleon scattering cross section by a factor.

hep-ph↗

arXiv2016

Single and double production of the Higgs boson at hadron and lepton colliders in minimal composite Higgs models

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

hep-ph↗

arXiv2016

Diphoton excess at 750 GeV in an extended scalar sector

We discuss an extended scalar model which explains the recent results of diphoton excess at 750 GeV at LHC Run II experiments. An additional singlet scalar boson with the mass of 750 GeV, which couples to top quarks via a dimension five operator, is produced via gluon fusion and decays into two photons via loop contributions of a number of (multiply) charged scalar bosons. Origin of such a dimension five operator would be, for example, in the context of composite Higgs models. The excess can be explained without contradicting the data from LHC Run I and also theoretical consistencies such as perturbative unitarity and charge non-breaking.

hep-ph↗

arXiv2015

R-Parity Conserving Supersymmetric Extension of the Zee Model

We extend the Zee model, where tiny neutrino masses are generated at the one loop level, to a supersymmetric model with R-parity conservation. It is found that the neutrino mass matrix can be consistent with the neutrino oscillation data thanks to the nonholomorphic Yukawa interaction generated via one-loop diagrams of sleptons. We find a parameter set of the model, where in addition to the neutrino oscillation data, experimental constraints from the lepton flavor violating decays of charged leptons and current LHC data are also satisfied. In the parameter set, an additional CP-even neutral Higgs boson other than the standard-model-like one, a CP-odd neutral Higgs boson, and two charged scalar bosons are light enough to be produced at the LHC and future lepton colliders. If the lightest charged scalar bosons are mainly composed of the SU(2)_L-singlet scalar boson in the model, they would decay into e nu and mu nu with 50% of a branching ratio for each. In such a case, the relation among the masses of the charged scalar bosons and the CP-odd Higgs in the minimal supersymmetric standard model approximately holds with a radiative correction. Our model can be tested by measuring the specific decay patterns of charged scalar bosons and the discriminative mass spectrum of additional scalar bosons.

hep-ph↗

arXiv2015

Beyond the SM phenomena and the extended Higgs sector based on the SUSY gauge theory with confinement

We propose a fundamental theory whose low-energy effective theory provides a phenomenological description of electroweak baryogenesis, radiative neutrino mass generation, and dark matter. The model is based on SUSY SU(2)_H gauge theory with confinement, and the model contains new Z_2 discrete symmetry and Z_2-odd right-handed neutrino superfields. The Higgs sector in the low energy effective theory of this model below confinement scale is described by fifteen mesonic superfields of fundamental SU(2)_H doublets. We present a benchmark scenario of this model, where all the constraints from the current neutrino, dark matter, lepton flavour violation and LHC data are satisfied. We also discuss how to test the scenario by the future collider experiments.

hep-ph↗

arXiv2015

New resonance scale and fingerprint identification in minimal composite Higgs models

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

hep-ph↗

arXiv2014

Lepton flavor violation in the supersymmetric seesaw model after the LHC 8 TeV run

We study the lepton flavor violation in the supersymmetric seesaw model taking into account recent experimental improvements, especially for the Higgs boson mass measurement, direct searches of superpartners and the rare decay of B_s -> mu+ mu- at the LHC, the neutrino mixing angle of theta_{13} at the neutrino experiments, and the search of mu -> e gamma at the MEG experiment. We obtain the latest constraints on the parameters in the supersymmetry breaking terms and study the effect on the lepton flavor violating decays of tau -> mu gamma and mu -> e gamma. In particular, we consider two kinds of assumption on the structures in the Majorana mass matrix and the neutrino Yukawa matrix. In the case of the Majorana mass matrix proportional to the unit matrix, allowing non-vanishing CP violating parameters in the neutrino Yukawa matrix, we find that the branching ratio of tau -> mu gamma can be larger than 10^{-9} within the improved experimental limit of mu -> e gamma. We also consider the neutrino Yukawa matrix that includes the mixing only in the second and third generations, and find that a larger branching ratio of tau -> mu gamma than 10^{-9} is possible with satisfying the recent constraints.

hep-ph↗

arXiv2014

Radiative neutrino mass, dark matter and electroweak baryogenesis from the supersymmetric gauge theory with confinement

We propose a simple model to explain neutrino mass, dark matter and baryogenesis based on the extended Higgs sector which appears in the low-energy effective theory of a supersymmetric gauge theory with confinement. We here consider the SU(2)$_H$ gauge symmetry with three flavours of fundamental representations which are charged under the standard SU(3)$_C\times$ SU(2)$_L\times$U(1)$_Y$ symmetry and a new discrete $Z_2$ symmetry. We also introduce $Z_2$-odd right-handed neutrino superfields in addition to the standard model matter superfields. The low-energy effective theory below the confinement scale contains the Higgs sector with fifteen composite superfields, some of which are $Z_2$-odd. When the confinement scale is of the order of ten TeV, electroweak phase transition can be sufficiently of first order, which is required for successful electroweak baryogenesis. The lightest $Z_2$-odd particle can be a new candidate for dark matter, in addition to the lightest $R$-parity odd particle. Neutrino masses and mixings can be explained by the quantum effects of $Z_2$-odd fields via the one-loop and three-loop diagrams. We find a benchmark scenario of the model, where all the constraints from the current neutrino, dark matter, lepton flavour violation and LHC data are satisfied. Predictions of the model are shortly discussed.

hep-ph↗