Search for the Lepton-Flavor-Violating Leptonic B Decays B^0 -> \mu^\pm \tau^\mp and B^0 -> \mu^\pm \tau^\mp

TL;DR

This study searched for lepton-flavor-violating B meson decays into muon or electron and tau leptons, setting upper limits on their branching ratios due to no observed signals in 9.6 million BBbar events.

Contribution

First search for these specific lepton-flavor-violating B decays, establishing new upper limits on their branching fractions.

Findings

No evidence of the decays was found.

Upper limits on branching ratios were set: <3.8×10^-5 for B^0 -> μ± τ∓ and <1.1×10^-4 for B^0 -> e± τ∓.

Results constrain new physics models predicting such decays.

Abstract

We have searched a sample of 9.6 million BBbar events for the lepton-flavor-violating leptonic B decays, B^0 -> \mu^\pm \tau^\mp and B^0 -> e^\pm \tau^\mp. The \tau-lepton was detected through the decay modes \tau -> \ell\nu\bar\nu, where \ell = e, \mu. There is no indication of a signal, and we obtain the 90% confidence level upper limits [Br(B^0 -> \mu^\pm \tau^\mp)] < 3.8 X 10^-5 and [Br(B^0 -> e^\pm \tau^\mp)] < 1.1 X 10^-4.