Search for Lepton Flavor Violating Tau Decays into Three Leptons with 719 Million Produced Tau+Tau- Pairs

TL;DR

This study searches for rare tau lepton decays into three leptons, finding no evidence and setting upper limits on their occurrence, which constrains new physics models involving lepton flavor violation.

Contribution

First comprehensive search for tau to three lepton decays using Belle data, establishing the most stringent upper limits to date.

Findings

No evidence of lepton-flavor-violating tau decays.

Set upper limits on branching fractions between 1.5 x 10^-8 and 2.7 x 10^-8.

Results constrain theories predicting lepton flavor violation.

Abstract

We present a search for lepton-flavor-violating tau decays into three leptons (electrons or muons) using 782 fb^-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. No evidence for these decays is observed and we set 90% confidence level upper limits on the branching fractions between 1.5 x 10^-8 and 2.7 x 10^-8.