Electroweak-scale mirror fermions, $\mu \to e\gamma$ and $\tau \to \mu \gamma$

Abstract

The Lepton Flavour Violating (LFV) processes $\mu \to e\gamma$ and $\tau \to \mu \gamma$ are estimated in a model of electroweak-scale right-handed neutrinos. The present bounds on the branching ratios, $B(\mu \to e\gamma )<1.2\times 10^{-11}$, $B(\tau \to \mu \gamma )<6.8\times 10^{-8}$ (BaBar) and $<4.5\times 10^{-8}$ (Belle), puts strong constraints on the parameters of the model. This constraint links low energy rare decay processes to high-energy phenomena (e.g. decay lengths of the mirror charged leptons which are important in the search for the telltale like-sign dilepton events present in the model of electroweak-scale right-handed neutrinos).

Comments: 8 double-column pages, 1 embedded figure. Version accepted for publication in Phys. Lett. B includes the following additions: one table, a few remarks, and three references