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Kazuya Ishikawa

Publications and source records attributed to Kazuya Ishikawa.

5 recordsLinked to original sources

Prospects for Higgs- and Z-resonant Neutralino Dark Matter

In the minimal supersymmetric standard models, neutralino dark matter with mass of $m_χ\sim m_Z/2\sim 45$ GeV and $m_χ\sim m_h/2\sim 62$ GeV can have the thermal relic abundance $Ω_{χ_1}h^2\simeq 0.120$ via the $Z$- and Higgs-resonant annihilations, respectively, while avoiding all the current constraints. Phenomenology of such scenarios is determined only by three parameters, Bino mass $M_1$, Higgsino mass $μ$, and $\tanβ$, in the limit that all other supersymmetric particles and heavy Higgs bosons are decoupled. In this paper, we comprehensively study the constraints and future prospects of the search for such Higgs- and $Z$-resonant neutralino dark matter. It is shown that almost all the parameter space of the scenario will be probed complementarily by the LHC search for the chargino and neutralinos, the direct detection experiments, and the Higgs invisible decay search at the ILC.

hep-ph↗

Towards a Scale Free Electroweak Baryogenesis

We propose a new electroweak baryogenesis scenario in high-scale supersymmetric (SUSY) models. We consider a singlet extension of the minimal SUSY standard model introducing additional vector-like multiplets. We show that the strongly first-order phase transition can occur at a high temperature comparable to the soft SUSY breaking scale. In addition, the proper amount of the baryon asymmetry of the universe can be generated via the lepton number violating process in the vector-like multiplet sector. The typical scale of our scenario, the soft SUSY breaking scale, can be any value. Thus our new electroweak baryogenesis scenario can be realized at arbitrary scales and we call this scenario as a scale free electroweak baryogenesis. This soft SUSY breaking scale is determined by other requirements. If the soft SUSY breaking scale is O(10) TeV, our scenario is compatible with the observed mass of the Higgs boson and the constraints by the electric dipole moments measurements and the flavor experiments. Furthermore, the singlino can be a good candidate of the dark matter.

hep-ph↗

Reconstruction of Vector-like Top Partner from Fully Hadronic Final States

We investigate the potential to search for the vector-like top partner in fully hadronic final states at the LHC. An algorithm is developed that kinematically reconstructs the vector-like top. We show that for moderate masses and a large branching fraction into the top quark and Higgs boson, the reconstruction works with good quality.

hep-ph↗

Singlino Resonant Dark Matter and 125 GeV Higgs Boson in High-Scale Supersymmetry

We consider a singlino Dark Matter (DM) scenario in a singlet extension model of the Minimal Supersymmetric Standard Model, which is so-called the Nearly MSSM (nMSSM). We find that with high-scale supersymmetry breaking the singlino can obtain a sizable radiative correction to the mass, which opens a window for the DM scenario with resonant annihilation via the exchange of the Higgs boson. We show that the current DM relic abundance and the Higgs boson mass can be explained simultaneously. This scenario can be fully probed by XENON1T.

hep-ph↗

Gauge Mediation Models with Vectorlike Matters at the LHC

Gauge mediation model with vectorlike matters (V-GMSB) is one of the few viable SUSY models that explains the 126 GeV Higgs boson mass and the muon anomalous magnetic moment simultaneously. We explore exclusion bounds on V-GMSB model from latest LHC SUSY searches.

hep-ph↗