Search for Lepton-Flavor-Violating tau Decays into a Lepton and a Vector Meson

TL;DR

This study searches for rare tau lepton decays into a lepton and a vector meson, setting upper limits on their occurrence rates due to no observed signals.

Contribution

First comprehensive search for tau lepton flavor-violating decays into a lepton and vector mesons using Belle data, establishing new upper limits on branching fractions.

Findings

No evidence of lepton-flavor-violating tau decays found.

Set upper limits on branching fractions between 1.2 and 8.4 times 10^{-8}.

Results constrain new physics models predicting such decays.

Abstract

We search for lepton-flavor-violating tau-> ell V^0 decays, where ell is an electron or muon and V^0 is one of the vector mesons rho^0, phi, omega, K*0 and K*0-bar. We use 854 fb^{-1} of data collected with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. No evidence for a signal is found in any decay mode, and we obtain 90% confidence level upper limits on the individual branching fractions in the range (1.2-8.4)*10^{-8}.