Upper Bound on the Decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mstyle displaystyle="false"><mml:mi>τ</mml:mi><mml:mo>→</mml:mo><mml:mi>μ</mml:mi><mml:mi>γ</mml:mi></mml:mstyle></mml:math>from the Belle Detector

A search for the lepton-flavor-violating decay tau-->microgamma using a data sample of 86.3 fb(-1) accumulated by the Belle detector at KEK shows no evidence for a signal, and an upper limit for the branching fraction of B(tau--> microgamma)<3.1 x 10(-7) is set.

Abstract

We have performed a search for the lepton-flavor-violating decay tau-->microgamma using a data sample of 86.3 fb(-1) accumulated by the Belle detector at KEK. No evidence for a signal is seen, and we set an upper limit for the branching fraction of B(tau-->microgamma)<3.1 x 10(-7) at the 90% confidence level.