A search for the decay modes B+/- to h+/- tau l

TL;DR

This paper searches for rare lepton flavor violating decays of B mesons into a hadron and a tau lepton, using a large data sample, but finds no evidence and sets upper limits on the decay rates.

Contribution

It introduces a novel search method for B meson decays involving tau leptons and sets new upper limits on these rare decay modes.

Findings

No evidence for B+/- to h+/- tau l decays was observed.

Upper limits on branching fractions are set at a few times 10^-5.

The analysis demonstrates the effectiveness of reconstructing tau momentum from B decay events.

Abstract

We present a search for the lepton flavor violating decay modes B+/- to h+/- tau l (h= K,pi; l= e,mu) using the BaBar data sample, which corresponds to 472 million BBbar pairs. The search uses events where one B meson is fully reconstructed in one of several hadronic final states. Using the momenta of the reconstructed B, h, and l candidates, we are able to fully determine the tau four-momentum. The resulting tau candidate mass is our main discriminant against combinatorial background. We see no evidence for B+/- to h+/- tau l decays and set a 90% confidence level upper limit on each branching fraction at the level of a few times 10^-5.