Search for the rare decay B to pi l+ l-

TL;DR

This paper reports a search for rare B meson decays to pi l+ l- and sets upper limits on their branching fractions, with no evidence of signal found in the analyzed data sample.

Contribution

The study provides new upper limits on the branching fractions of B to pi l+ l- and B to pi e mu decays, improving constraints on flavor-changing neutral currents and lepton-flavor violation.

Findings

No evidence for B to pi l+ l- decay was observed.

Upper limit on BF(B+ --> pi+ l+ l-) is 7.9 x 10^-8.

Upper limit on BF(B --> pi e mu) is 9.8 x 10^-8.

Abstract

We present results of a search for the rare flavor-changing neutral-current decay B --> pi l+ l-, based on a data sample corresponding to 209 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II B Factory. We reconstruct the four exclusive B decay modes B+ --> pi+ l+ l- and B0 --> pi0 l+ l-, where l is either an e or mu. We find no evidence for a signal, and we obtain the upper limit at 90% confidence level on the lepton-flavor--averaged branching fraction to be BF(B+ --> pi+ l+ l-) = 2 x tau_B+/tau_B0 x BF(B0 --> pi0 l+ l-) < 7.9 x 10-8. We also obtain an upper limit at 90% confidence level on the lepton-flavor--violating decay B --> pi e mu of BF(B --> pi e mu) < 9.8 x 10-8.