New Search for tau -> mu gamma and tau -> e gamma Decays at Belle

TL;DR

This paper reports a search for rare lepton flavor violating tau decays at Belle, setting new upper limits on their branching ratios due to no observed signals.

Contribution

First search at Belle for tau -> mu gamma and tau -> e gamma decays, establishing upper limits on their branching ratios.

Findings

No signal observed for the decays.

Upper limits set on branching ratios: 4.5x10^-8 for tau -> mu gamma.

Upper limit of 1.2x10^-7 for tau -> e gamma.

Abstract

We report on a search for the lepton flavor violating tau- -> mu- gamma and tau- -> e- gamma decays based on 535/fb of data accumulated at the Belle experiment. No signal is found and we set 90% confidence level upper limits on the branching ratios Br(tau- -> mu- gamma) < 4.5x10^-8 and Br(tau- -> e- gamma) < 1.2x10^-7.