Improved limits on lepton flavor violating tau decays to l phi, l rho, l K* and l K*bar

TL;DR

This paper reports improved upper limits on lepton flavor violating tau decays to a lepton and a vector meson, using a large dataset from the BaBar experiment, with no significant signal observed.

Contribution

The study provides the most stringent upper limits to date on branching fractions for tau decays to l V^0, advancing constraints on new physics models involving lepton flavor violation.

Findings

No evidence of lepton flavor violation observed.

Upper limits on branching fractions are set between 2.6 and 19 x 10^{-8}.

Results improve previous bounds on tau decay modes.

Abstract

We search for the neutrinoless, lepton-flavor-violating tau decays tau -> l V^0, where l is an electron or muon and V^0 is a vector meson reconstructed as phi -> K^+K^-, rho -> pi^+pi^-, K^* -> K^+pi^-, or K^*bar -> K^-pi^+. The analysis has been performed using 451 fb^{-1} of data collected at an e^+e^- center-of-mass energy near 10.58 GeV with the BaBar detector at the PEP-II storage rings. The number of events found in the data is compatible with the background expectation, and upper limits on the branching fractions are set in the range (2.6-19) x 10^{-8} at the 90% confidence level.