A Search for the Rare Decays B --> pi l+l- and B0 --> eta l+l-

TL;DR

This study searches for rare B meson decays into pi and eta mesons with lepton pairs, setting upper limits on their branching fractions due to no significant signals observed in a large data sample.

Contribution

The paper provides new upper limits on the branching fractions of B --> pi l+l- and B0 --> eta l+l- decays, improving constraints on flavor-changing neutral currents.

Findings

No significant signal observed for the decays.

Upper limits set on branching fractions at 90% confidence level.

Results constrain new physics models involving flavor-changing neutral currents.

Abstract

We present the results of a search for the rare flavor-changing neutral-current decays B --> pi l+l- (pi=pi+/-, pi0 and l = e,mu) and B0 --> eta l+l- using a sample of e+e- --> Y(4S) BB decays decays corresponding to 428 fb^-1 of integrated luminosity collected by the BABAR detector. No significant signal is observed, and we set an upper limit on the isospin and lepton-flavor averaged branching fraction of BF(B --> pi l+l-) < 7.0 x 10^-8 and a lepton-flavor averaged upper limit of BF(B0 --> eta l+l-) < 9.2 x 10^-8, both at the 90% confidence level. We also report 90% confidence level branching fraction upper limits for the individual modes B+ --> pi+ e+e-, B0 --> pi0 e+e-, B+ --> pi+ mu+mu-, B0 --> pi0 mu+mu-, B0 --> eta e+e-, and B0 --> eta mu+mu-.