A Search for the Decay B+ --> tau+ nu_tau

TL;DR

This paper reports a search for the rare decay B+ --> tau+ nu_tau using data from the BABAR detector, setting upper limits on its branching fraction due to no observed signal.

Contribution

The study provides the most stringent upper limits to date on the branching fraction of B+ --> tau+ nu_tau by combining multiple analyses.

Findings

No evidence for B+ --> tau+ nu_tau decay was observed.

Upper limit on BR(B+ --> tau+ nu_tau) < 2.6x10^{-4} at 90% CL.

Improved constraints on leptonic B meson decays.

Abstract

We search for the rare leptonic decay B+ --> tau+ nu_tau in a sample of 232x10^6 BBbar pairs collected with the BABAR detector at the SLAC PEP-II B-Factory. Signal events are selected by examining the properties of the B meson recoiling against the semileptonic decay B- --> D*0 l- nu_lbar. We find no evidence for a signal and set an upper limit on the branching fraction of BR(B+ --> tau+ nu_tau) < 2.8x10^{-4} at the 90% confidence level. We combine this result with a previous, statistically independent BABAR search for B+ --> tau+ nu_tau to give an upper limit of BR(B+ --> tau+ nu_tau) < 2.6x10^{-4} at the 90% confidence level.