Lepton flavor violation in the supersymmetric standard model with vectorlike leptons

Abstract

Lepton flavor violating processes are obtained from the mixing between ordinary leptons and vectorlike $\mathrm{SU}{(2)}_{L}$ doublet leptons which may originate in ${E}_{6}.$ The effects of this lepton mixing are, however, suppressed naturally by the hierarchy of the charged lepton masses. In the supersymmetric model, significant effects of lepton flavor violation may appear rather through slepton mixing, which is in the present case generated by radiative corrections with ordinary-exotic lepton couplings. We are especially interested in the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\mu}}e\ensuremath{\gamma}$ decay. In the model without the bare mass term of vectorlike leptons, the supersymmetric contributions are rather suppressed due to the approximate $\mathrm{U}{(1)}_{e}\ifmmode\times\else\texttimes\fi{}\mathrm{U}{(1)}_{\ensuremath{\mu}}.$ It is, however, remarkable that they are substantially enhanced by ${\mathrm{tan}}^{6}\ensuremath{\beta}.$ Then, $\mathrm{Br}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\mu}}e\ensuremath{\gamma})$ might be comparable to the experimental bound for large tan \ensuremath{\beta}. In the model with the bare mass term, much larger contributions are obtained through slepton mixing. These investigations show that the supersymmetric effects on lepton flavor violation due to the vectorlike leptons can be observed in the near future experiments.