Search for the Lepton Number Violating Decay Tau to Mu Gamma

TL;DR

This study conducted a search for the lepton number violating decay Tau to Mu Gamma using BaBar data, setting an upper limit on its branching ratio due to no observed signal.

Contribution

First search for Tau to Mu Gamma decay using BaBar data, establishing an upper limit on its branching ratio with a large dataset of tau pairs.

Findings

No evidence for Tau to Mu Gamma decay was observed.

Set an upper limit on the branching ratio at 2.0 x 10^-6.

Analyzed 56 million tau pair events with specific detection efficiency.

Abstract

Using data collected with the BaBar detector between 1999 and 2001, we describe a preliminary search for the neutrinoless decay Tau to Mu Gamma. This data sample includes data collected both on and off the Upsilon(4S) resonance and corresponds to 56 million produced tau pair events. The search has an efficiency of 5.2 +- 0.1(MCstat) +- 0.5(sys) % and an expected background rate of 7.8 +- 1.4 events. We select 13 events in the final sample. As there is no evidence for a signal in this data, we set a preliminary upper limit of B(Tau to Mu Gamma) < 2.0 x 10^-6 @90% CL.