Study of the Lepton Flavor Violating Decay $\tau^{-} \to \mu^{-} \eta$

TL;DR

This paper reports a search for lepton flavor violation in tau decays to a muon and eta meson, using BABAR data, setting a new upper limit on the decay's branching ratio.

Contribution

First search for $ au^- o \mu^- \eta$ decay using BABAR data, establishing an upper limit on its branching ratio.

Findings

No evidence of the decay was observed.

An upper limit of 1.6×10⁻⁷ was set on the branching ratio.

The results constrain new physics models predicting lepton flavor violation.

Abstract

We present the preliminary results from the search of the non-conservation of lepton flavor number in the decay of a $\tau$ to a lighter mass lepton and a pseudo-scalar meson, performed using $e^+e^- \to \tau^+\tau^-$ events collected at a center-of-mass energy near 10.58 GeV with the BABAR detector at the SLAC PEP-II $e^+e^-$ storage ring. No evidence of such a signal has been found in the data sample corresponding to a luminosity of 314.5 fb$^{-1}$, and we set an upper limit of $1.6\times 10^{-7}$ at 90% confidence level on the decay of $\tau^- \to \mu^-\eta$.