arXiv subjects

Daijiro Suematsu

Publications and source records attributed to Daijiro Suematsu.

66 records · Page 4Linked to original sources

arXiv1998

Vacuum Structure of the $μ$-Problem Solvable Extra U(1) Models

Vacuum structure and related phenomenological features are investigated in $μ$-problem solvable supersymmetric extra U(1) models. We present a framework for the analysis of their vacuum structure taking account of an abelian gauge kinetic term mixing, which can potentially modify a scalar potential and $Z^0$ gauge interactions. Applying this to data of the precise measurements at LEP, we constrain an allowed region in a space of Higgs vacuum expectation values based on consistency with potential minimum conditions. We find that such a region is confined into rather restricted one. Bounds on masses of an extra U(1) gauge boson and the lightest neutral Higgs boson are predicted. Renormalization group equations for gauge coupling constants and gaugino soft masses in an abelian gauge sector are also discussed in relation to the gauge kinetic term mixing in some detail.

hep-ph↗

arXiv1998

Phenomenological neutrino mass matrix for neutrino oscillations and dark matter

A phenomenological neutrino mass matrix is proposed to explain the solar and atmospheric neutrino deficits and to present the neutrino as a candidate of hot dark matter in the $3ν_L+3ν_R$ framework. The realization of mixing angles which can explain the solar and atmospheric neutrino problems is taken as the first criterion in this construction. The differences among neutrino mass eigenvalues are introduced as a perturbation. In this scheme the structure of a charged lepton mass matrix is not severely constrained by the solar and atmospheric neutrino data.

hep-ph↗

arXiv1997

$μ\to e γ$ in supersymmetric multi U(1) models with an abelian gaugino mixing

A lepton flavor violating process $μ\to eγ$ is investigated in the supersymmetric extra U(1) models, which often appear as the low energy effective models of superstring and can potentially solve the $μ$-problem. The branching ratio of this process is calculated. It is numerically estimated and compared with that of the MSSM. In this study we take account of an abelian gaugino kinetic term mixing and discuss its influence on this process. The possibility to find the extra gauge structure through this process is discussed.

hep-ph↗

arXiv1997

Neutralino decay in the $μ$-problem solvable extra U(1) models

We study the neutralino decay in the supersymmetric extra U(1) models which can solve the $μ$-problem. In these models the neutralino sector is extended at least into six components by an extra U(1) gaugino and a superpartner of a singlet Higgs. Focussing on its two lower mass eigenstates $\tildeχ_2^0$ and $\tildeχ_1^0$, decay processes such as a tree level three body decay $\tildeχ_2^0\to \tildeχ_1^0 f\bar f$ and a one-loop radiative decay $\tildeχ_2^0\to \tildeχ_1^0γ$ are estimated. We investigate the condition under which the radiative decay becomes the dominant mode and also numerically search for such parameter regions. In this analysis we take account of the abelian gaugino kinetic term mixing. We suggest that the gaugino mass relation $M_W\sim M_Y$ may not be necessary for the radiative decay dominance in the extra U(1) models.

hep-ph↗

arXiv1997

Effect on the electron EDM due to abelian gauginos in SUSY extra U(1) models

The electric dipole moment of an electron (EDME) is investigated in the supersymmetric extra U(1) models. Neutralino sector is generally extended in these models and then the neutralino contribution will be important for the analysis of the EDME. Kinetic term mixings of abelian gauginos are taken into account in our analysis. Numerical results for the extra U(1) models show that the EDME can be affected by the extra U(1) in a certain range of soft supersymmetry breaking parameters even if the extra U(1) gauge boson is heavy. The EDME may be a clue to find an extended gauge structure in the supersymmetric models.

hep-ph↗

arXiv1996

Neutrino Oscillation based on the Mixings with a Heavy Right-Handed Neutrino

We study a consistent explanation for both deficits of solar neutrino and atmospheric neutrino due to the neutrino oscillation induced by the mixing of light neutrinos with a heavy right-handed neutrino. We propose such a phenomenological neutrino mass matrix that realizes this scenario in the simple three generation left- and right- handed neutrino framework. Although this model contains only one nonzero mass eigenvalue $\sim$ 10 eV for these light neutrino states at the first approximation level, it can be expected to explain consistently both deficiency due to the appropriate higher order corrections. A suitable hot dark matter candidate is naturally included in it as its own feature.

hep-ph↗

arXiv1996

Flavor Structure of Soft SUSY Breaking Parameters

Flavor structure of soft supersymmetry breaking parameters is studied in a certain type of effective supergravity theory derived from moduli/dilaton dominated supersymmetry breaking. Some interesting sum rules for soft scalar masses are presented. They constrain their flavor structure and predict some interesting patterns appeared in soft scalar masses in the non-universal case. We also study the alignment phenomena in the flavor space of soft breaking parameters due to Yukawa couplings and discuss their phenomenological consequences.

hep-ph↗

arXiv1996

Proton Stability and Small Neutrino Mass in String Inspired $E_6$ Models

We propose a new possibility to realize simultaneously the sufficient proton stability and the interesting structure of neutrino mass matrix in superstring inspired $E_6$ models. In this model the leptons and Higgs fields are assigned to a fundamental representation {\bf 27} in the different way among generations. Two pairs of Higgs doublets naturally remain light from three generation ones by imposing certain discrete symmetries, although all extra color triplets become sufficiently heavy. Under these symmetries suitable $μ$-terms to bring appropriate vacuum expectation values are prepared and the dangerous FCNC is avoidable. Some related phenomena to this model, especially, the structure of neutrino mass matrix are also discussed.

hep-ph↗

arXiv1995

Chaotic Inflation based on an Abelian D-flat Direction

We study the inflation due to the D-flat direction of an extra $U(1)$. This scenario is a hybrid of a right-handed sneutrino inflaton scenario and a gauge non-singlet inflaton scenario. The inflaton is a gauge non-singlet field which induces a right-handed neutrino mass spontaneously through an extra $U(1)$ D-flat direction. This right-handed neutrino mass can explain the solar neutrino problem. The reheating temperature resulting from the decay of the coherent oscillation of the right-handed sneutrino is sufficiently high so that the baryogenesis based on the lepton number asymmetry can be applicable. We also discuss the realistic model building.

hep-ph↗

arXiv1994

Radiative Symmetry Breaking in a Supersymmetric Model with an Extra $U(1)$

Radiative symmetry breaking is studied in a superstring-inspired supersymmetric model which is extended with a low energy extra $U(1)$ symmetry. In this model the $μ$-problem is radiatively solved in an automatic way. The right-handed neutrino can be heavy and the seesaw mechanism will produce the small neutrino mass which makes the MSW solution applicable to the solar neutrino problem. We search a parameter region which has the favorable feature for the radiative symmetry breaking at the weak scale. Rather wide parameter region is found to be allowed. The upper bound of the extra $Z$ boson mass is estimated as $M_{Z_2} \le 2000$~GeV for a top mass range $ 150~{\rm GeV} \le m_t \le 190~{\rm GeV}$. Some phenomenological features of the extra $Z$ boson are also presented.

hep-ph↗

arXiv1992

Neutrino Magnetic Moment Model and Solar Neutrino Problem

We examine the time variation problem of solar neutrinos in the spin-flavour precession mechanism taking into account the $ν_e$-$ν_μ$ mixing. The models with the small and large mixing angle are studied. It shows that the models which realize $m_{ν_eν_e} \sim m_{ν_μν_μ} \ll m_{ν_eν_μ}$ and $m_{ν_eν_e} \sim m_{ν_μν_μ} {^>_\sim} m_{ν_eν_μ}$ seem to have preferable time variation features. It is very interesting that the former type of models can give the large magnetic moment to neutrinos and also suppress the radiative mass correction naturally.

hep-ph↗

arXiv1992

Strong CP-Problem in Superstring Theory

We apply the solution for the strong CP-problem in the 4-dimensional superstring theory recently proposed by Ib${\rm\acute{a}\tilde{n}}$ez and L${\rm\ddot{u}}$st to Calabi-Yau type models and study its phenomenological aspects. In Calabi-Yau type models there seem to be phenomenologically difficult problems in the axion decoupling from the neutral gauge currents and the compatibility between the proton stability and the cosmological bound on the axion. DFSZ type invisible axion mechanism which works without heavy extra colored fields may be more promising than KSVZ axion in the viewpoint of proton stability.

hep-ph↗