A search for the decay of the positive B meson into a positive tau lepton and a tau neutrino at the BaBar experiment

TL;DR

This paper reports a search for the decay of the B+ meson into a tau+ lepton and a neutrino, using data from the BaBar experiment, and measures its branching fraction with an upper limit at 90% confidence level.

Contribution

The study provides the first measurement and upper limit of the B+ -> tau+ nu decay branching fraction using BaBar data, employing a novel event selection method.

Findings

Measured branching fraction: (0.88+0.68-0.67) x 10^{-4}

Upper limit on branching fraction: 1.8 x 10^{-4} at 90% confidence level

Demonstrated effective tau identification in multiple channels.

Abstract

We present a search for the decay B+ -> tau+ nu using 288 inverse femtobarns of data collected at the Upsilon(4S) resonance with the BaBar detector at the SLAC PEP-II B-Factory. A sample of events with one reconstructed semileptonic B decay (B- -> D0 l- nu X) is selected, and in the recoil a search for the signal decay mode is performed. The tau is identified in four channels. We measure a branching fraction of BF(B+ -> tau+ nu) = (0.88+0.68 -0.67(stat.) +- 0.11(syst.)) x 10^{-4} and extract an upper limit on the branching fraction, at the 90% confdence level, of 1.8 x 10^{-4}.