$\mu \to e \gamma$ and $\tau \to l \gamma$ decays in the fermion triplet seesaw model

TL;DR

This paper analyzes lepton flavor violating decays in fermion triplet seesaw models, showing that upcoming experiments could detect these decays without conflicting with current bounds, implying additional sources of lepton flavor violation.

Contribution

It evaluates decay rates of $oldsymbol{ ext{mu} o e ext{gamma}}$ and $oldsymbol{ au o l ext{gamma}}$ in fermion triplet seesaw models and discusses implications for lepton flavor violation.

Findings

Decay rates are generally below current experimental limits.

Observation of these decays would suggest additional lepton flavor violation sources.

Detection would challenge the assumption that triplet fermions are the sole source.

Abstract

In the framework of the seesaw models with triplets of fermions, we evaluate the decay rates of $\mu \to e \gamma$ and $\tau \to l \gamma$ transitions. We show that although, due to neutrino mass constraints, those rates are in general expected to be well under the present experimental limits, this is not necessarily always the case. Interestingly enough, the observation of one of those decays in planned experiments would nevertheless contradict bounds stemming from present experimental limits on the $\mu \to eee$ and $\tau \to 3 l$ decay rates. Such detection of radiative decays would therefore imply that there exist sources of lepton flavour violation not associated to triplet fermions.