UC Berkeley

A search for the rare flavor-changing neutral current process B-→Λpνν using data from the BABAR experiment has been performed. A total of 424 fb-1 of e+e-collision data collected at the center-of-mass energy of the Ï'(4S) resonance is used in this study, corresponding to a sample of (471±3)×106 BB pairs. Signal B-→Λpνν candidates are identified by first fully reconstructing a B+ decay in one of many possible exclusive decays to hadronic final states, then examining detector activity that is not associated with this reconstructed B+ decay for evidence of a signal B-→Λpνν decay. The data yield is found to be consistent with the expected background contribution under a null signal hypothesis, resulting in an upper limit of B(B-→Λpνν)<3.0×10-5 at the 90% confidence level.