Search for Lepton Flavor Violating tau Decays into Three Leptons

TL;DR

This study searches for rare lepton-flavor-violating tau decays into three leptons using Belle data, setting new upper limits that significantly improve previous constraints, with no evidence of such decays observed.

Contribution

First search for tau lepton flavor violation into three leptons using Belle data, establishing the most stringent upper limits to date.

Findings

No evidence for lepton-flavor-violating tau decays was observed.

Set upper limits on branching fractions between 2.0x10^{-8} and 4.1x10^{-8}.

Improved previous upper limits by factors of 4.9 to 7.0.

Abstract

We search for lepton-flavor-violating tau decays into three leptons (electron or muon) using 535 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 2.0x10^{-8} and 4.1x10^{-8}. These results improve the best previously published upper limits by factors from 4.9 to 7.0.