Search for tau -> e gamma decay at Belle

TL;DR

This study searched for the rare tau -> e gamma decay at Belle but found no evidence, setting an upper limit on its branching fraction, which constrains new physics models involving lepton flavor violation.

Contribution

First search for tau -> e gamma decay at Belle, establishing the most stringent upper limit to date on its branching fraction.

Findings

No signal observed for tau -> e gamma decay.

Upper limit on branching fraction set at 3.9 x 10^-7.

Results constrain theories predicting lepton flavor violation.

Abstract

We have searched for the lepton-flavor-violating decay tau -> e gamma using a data sample of 86.7/fb collected with the Belle detector at the KEKB asymmetric e^+ e^- collider. No evidence for a signal is obtained, and we set an upper limit for the branching fraction Br(tau -> e gamma) < 3.9 x 10^-7 at the 90% C.L.