Search for Lepton Flavor Violation in the Decay tau -> mu gamma

TL;DR

This paper reports a search for lepton flavor violation in tau decays, specifically tau -> mu gamma, using a large dataset from the BABAR detector, and sets a new upper limit on its branching ratio.

Contribution

The study provides the most stringent upper limit to date on the branching ratio of tau -> mu gamma decay, improving constraints on new physics models.

Findings

No evidence for tau -> mu gamma decay was observed.

Upper limit on BR(tau -> mu gamma) < 6.8 x 10^-8 at 90% CL.

Large dataset of 2.07 x 10^8 tau pairs analyzed.

Abstract

A search for the nonconservation of lepton flavor number in the decay tau -> mu gamma has been performed using 2.07 x 10^8 e+e- -> tau+ tau- events produced at a center-of-mass energy near 10.58 GeV with the BABAR detector at the PEP-II storage ring. We find no evidence for a signal and set an upper limit on the branching ratio of BR(tau -> mu gamma) < 6.8 x 10^-8 at 90% confidence level.