Lepton-Flavor Violation via Right-Handed Neutrino Yukawa Couplings in Supersymmetric Standard Model

Abstract

Various lepton-flavor violating (LFV) processes in the supersymmetric standard model with right-handed neutrino supermultiplets are investigated in detail. It is shown that large LFV rates are obtained when $\tan β$ is large. In the case where the mixing matrix in the lepton sector has a similar structure as the Kobayashi-Maskawa matrix and the third-generation Yukawa coupling is as large as that of the top quark, the branching ratios can be as large as $Br(μ\rightarrow eγ)\simeq 10^{-11}$ and $Br(τ\rightarrowμγ)\simeq 10^{-7}$, which are within the reach of future experiments. If we assume a large mixing angle solution to the atmospheric neutrino problem, rate for the process $τ\rightarrowμγ$ becomes larger. We also discuss the difference between our case and the case of the minimal $SU(5)$ grand unified theory.