Junichiro Kawamura 교수

We consider the Standard Model (SM) with the addition of a $\mathrm{U}(1{)}^{\ensuremath{'}}$ gauge symmetry and a complete fourth family of quarks and leptons which are vectorlike with respect to the full $\mathrm{SU}(3{)}_{\mathrm{C}}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(2{)}_{\mathrm{L}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}_{\mathrm{Y}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1{)}^{\ensuremath{'}}$ gauge symmetry. The model provides a unified explanation of experimenta

We study a lepton portal dark matter model, motivated by the deviation of the $W$ boson mass reported by the CDF collaboration. We introduce vectorlike leptons and a scalar dark matter (DM) that exclusively couples to the extra leptons and muon. The one-loop corrections induced by the new particles can shift the $W$ boson mass. Besides, the discrepancy in the muon anomalous magnetic moment and the DM density can simultaneously be explained by this setup, if the vectorlike lepton is lighter than

In this paper, we summarize phenomenology in lepton portal dark matter (DM) models, where DM couples to leptons and extra leptons/sleptons. There are several possible setups: a DM field is either a complex/real scalar or a Dirac/Majorana fermion, and chiralities of leptons that couple to the DM are different according to the spin of the DM. We discuss the prediction of each model and compare it with the latest experimental constraints from the DM detections, the LHC, and the flavor experiments.

Recently, the LHCb Collaboration has reported the excesses in the $b\ensuremath{\rightarrow}sll$ processes. One of the promising candidates for new physics to explain the anomalies is the extended Standard Model (SM) with vectorlike quarks and leptons. In that model, Yukawa couplings between the extra fermions and SM fermions are introduced, adding extra scalars. Then, the box diagrams involving the extra fields achieve the $b\ensuremath{\rightarrow}sll$ anomalies. It has been known that the exc

We present an in-depth analysis of a recently proposed Standard Model extension with a complete fourth generation of quarks and leptons, which are vectorlike with respect to the Standard Model gauge group and charged under a new spontaneously broken vectorlike $\mathrm{U}(1{)}^{\ensuremath{'}}$ gauge symmetry. The model is designed to explain the known muon anomalies, i.e., the observed deviations from Standard Model predictions in the anomalous magnetic moment of the muon, $\mathrm{\ensuremath{

We propose models in which the hierarchical structures of the masses and mixing in both quark and lepton sectors are explained by the S4′ modular flavor symmetry near the fixed point τ∼i∞. The model provides the first explicit example which explains hierarchies of both quarks and leptons from single modular flavor symmetry. The hierarchies are realized by powers of ϵ=e2πiτ/4=O(0.01) and 2Imτ∼5, where τ being the modulus. The small parameter ϵ plays a role of flavon in the Froggatt-Nielsen mechan

Recently, the ATLAS and CMS collaborations report excesses around 750 GeV in the diphoton channels. This might be the evidence which reveals new physics beyond the Standard Model. In this paper, we consider models with a 750 GeV scalar and vectorlike particles, which couple each other through Yukawa couplings. The decay of the scalar to diphoton is given by the loop diagrams involving the extra colored particles. We investigate not only the setup required by the excesses, but also the LHC constr

A bstract We study the lepto-axiogenesis scenario in the minimal supersymmetric KSVZ axion model. Only one Peccei-Quinn (PQ) field and vector-like fields are introduced besides the MSSM with the type-I see-saw mechanism. The PQ field is stabilized by the radiative correction induced by the Yukawa couplings with the vector-like fields introduced in the KSVZ model. We develop a way to follow the dynamics of the PQ field, in particular we found a semi-analytical solution which describes the rotatio

We propose a novel possibility to detect a very distinctive signal with more than four muons originating from pair-produced vector-like leptons decaying to a muon-philic ${Z}^{\ensuremath{'}}$ boson. These new particles are good candidates to explain the anomalies in the muon anomalous magnetic moment and the $b\ensuremath{\rightarrow}s\ensuremath{\ell}\ensuremath{\ell}$ processes. The doublet (singlet) vector-like leptons lighter than 1.3 (1.0) TeV are excluded by the latest data at the LHC if

We study the effects of vectorlike leptons on the $W$-boson mass in a model with a vectorlike $U(1{)}^{\ensuremath{'}}$ gauge symmetry. This model provides simultaneous explanations for the recent anomalies in the muon anomalous magnetic moment and the semileptonic decays of $B$ mesons. We find that the recent result of the $W$-boson mass's precise measurement at CDF can be explained if the charged (neutral) vectorlike lepton is lighter than 250 (80) GeV. The light vectorlike leptons may not be

We investigate exclusion limits on the nonuniversal gaugino mass scenario in the minimal supersymmetric standard model (MSSM), according to the latest results of the superparticle search at the LHC8 and the LHC13. In this scenario, suitable ratios of wino to gluino mass can realize the observed value of the Higgs boson mass, while keeping a small $\ensuremath{\mu}$ parameter. Such a small $\ensuremath{\mu}$ parameter corresponds to the mass of Higgsino, so that lightest neutralino and chargino a

We study dark matter physics in the Minimal Supersymmetric Standard Model with non-universal gaugino masses at the unification scale. In this scenario, the specific ratio of wino and gluino masses realizes the electro-weak scale naturally and achieves 125 GeV Higgs boson mass. Then, relatively light higgsino is predicted and the lightest neutral particle, that is dominantly given by the neutral component of higgsino, is a good dark matter candidate. The direct detection of the dark matter is sen

We propose a new search strategy for higgsinos. Assuming associated production of higgsino-like pairs with a W or Z boson, we search in the missing energy plus hadronically-tagged vector boson channel. We place sensitivity limits for (HL-)LHC searches assuming O(1–3.5GeV) mass differences between the lightest neutral and charged states. We point out that using the ETmiss distribution significantly increases the sensitivity of this search. We find the higgsinos up to 110 (210) GeV can be excluded

In this paper we construct supersymmetric Pati-Salam (PS) models containing the minimal supersymmetric standard model and an invisible axion. The models include two discrete symmetries, ${\mathbb{Z}}_{4}^{R}\ifmmode\times\else\texttimes\fi{}{\mathbb{Z}}_{N}$, which maintain the quality of the accidental Peccei-Quinn (PQ) symmetry and thus the solution to the strong $CP$ problem. We require that the discrete anomaly conditions are satisfied for both ${\mathbb{Z}}_{4}^{R}\ifmmode\times\else\textti

We extend the Standard Model (SM) with parity symmetry, motivated by the strong CP problem and dark matter. In our model, parity symmetry is conserved at high energy by introducing a mirror sector with the extra gauge symmetry, SU(2)_R × U(1)_R. The charges of SU(2)_R × U(1)_R are assigned to the mirror fields in the same way as in the SM, but the chiralities of the mirror fermions are opposite to respect the parity symmetry. The strong CP problem is resol