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

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.