arXiv subjects

Takeshi Nihei

Publications and source records attributed to Takeshi Nihei.

22 records · Page 2Linked to original sources

arXiv1997

Effect of SUSY phases on the $B^0_d - \bar{B}^0_d$ mixing in the minimal supergravity model

We investigate the effect of SUSY phases ($θ_A$ and $θ_μ$) on the $B^0_d - \bar{B}^0_d$ mixing in the minimal supergravity model. It is known that the complex phase $θ_A$ $=$ arg($A$) ($A$ is the universal coefficient of the trilinear scalar couplings) is essentially unconstrained by the electric dipole moment experiment, while the phase $θ_μ$ $=$ arg($μ$) ($μ$ is the supersymmetric Higgsino mass) is strongly constrained to zero. We found that $θ_A$ does not affect the phase of the $B^0_d - \bar{B}^0_d$ mixing matrix element $M_{12}(B)$ by numerical analysis of the renormalization group equations. This means that the measurement of the $B^0_d - \bar{B}^0_d$ mixing at the future B-factory could give the direct information on the parameters of the CKM matrix even in the framework of the minimal supergravity model with the SUSY phase $θ_A$.

hep-ph↗

arXiv1995

$B^0$--$\overline{B}^0$ mixing and $ε_K$ parameter in the minimal supergravity model

\bb mixing and a CP violation parameter in \kk mixing $ε_K$ are studied in the minimal supergravity model. We solve the one-loop renormalization group equations for the minimal supersymmetric standard model (MSSM) parameters numerically in order to determine the masses and mixings of the supersymmetric particles, while all off-diagonal (generation mixing) elements and phases of Yukawa coupling matrices and those of squark mass matrices are taken into account. Applying the radiative electroweak symmetry breaking condition and phenomenological constraints including the recent measurement of the \bsg inclusive branching ratio, we obtain the allowed parameter region. We have found that the present constraints still allow a parameter region where both \bb mass splitting $ΔM_B$ and $ε_K$ are $\sim 20$\% larger than the standard model values. By explicit numerical calculations, we have also found that the complex phase of \bb mixing matrix element in this model is almost the same as the standard model value in a good accuracy in the whole allowed parameter region. It is shown that $ΔM_B$ and $ε_K$ can put useful constraints on the supersymmetry's parameter space when the Cabibbo-Kobayashi-Maskawa matrix elements are determined through the measurements of CP violations in $B$ decay with future $B$-factories.

hep-ph↗

arXiv1994

The Two Loop Long Range Effect on the Proton Decay Effective Lagrangian

We calculate the two loop long range effect on the proton decay effective Lagrangian. Numerical calculation for suppression factor gives $ A_L($2-loop$) = 0.321$ for the value of the strong coupling constant $ α_s(m_Z) = 0.116 $. Two loop effect to more general effective Lagrangian is also given.

hep-ph↗

arXiv1994

Flavor mixing in the gluino coupling and the nucleon decay

Flavor mixing in the quark-squark-gluino coupling is studied for the minimal SU(5) SUGRA-GUT model and applied to evaluation of the nucleon lifetime. All off-diagonal (generation mixing) elements of Yukawa coupling matrices and of squark/slepton mass matrices are included in solving numerically one-loop renormalization group equations for MSSM parameters, and the parameter region consistent with the radiative electroweak symmetry breaking condition is searched. It is shown that the flavor mixing in the gluino coupling for a large $\tanβ$ is of the same order of magnitude as the corresponding Kobayashi-Maskawa matrix element in both up-type and down-type sector. There exist parameter regions where the nucleon decay amplitudes for charged lepton modes are dominated by the gluino dressing process, while for all the examined regions the neutrino mode amplitudes are dominated by the wino dressing over the gluino dressing.

hep-ph↗