μ→eγdecay in an MSSM extension

Abstract

An analysis is given of the decay $\ensuremath{\mu}\ensuremath{\rightarrow}e+\ensuremath{\gamma}$ in an minimal supersymmetric standard model extension with a vectorlike generation. Here mixing with the mirrors allows the possibility of this decay. The analysis is done at the one-loop level with the exchange of charginos and neutralinos and of sleptons and mirror sleptons in the loops. A one-loop analysis with W- and Z-boson exchange and mirror leptons and neutrinos is also considered. The effects of $CP$-violating phases from the new sector on the decay $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ are analyzed in detail. The constraints arising from the current upper limit on the branching ratio $\mathcal{B}(\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma})$ from the MEG experiment of $2.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ (at 90% C.L.) on the parameter space of supersymmetry (SUSY) models and on vectorlike models are explored. Further, the MEG experiment is likely to improve the upper limit by an order of magnitude in the coming years. The improved limits will allow one to probe a much larger domain of the parameter space of the extended models.