Search for baryon- and lepton-number violation in $B$ decays using the {\sc BaBar} dataset

A search for the decay of a $B$ meson into a baryon and a lepton is performed, where the baryon is either a $\Lambda_c^+$ or a $\Lambda$, and the lepton is a muon or an electron. These decays violate both baryon and lepton number. This is the first search for these processes, and observation of a signal would indicate physics beyond the standard model. The search uses $(471\pm 1)\times 10^{6}$ $B\bar{B}$ pairs produced by the PEP-II $e^+e^-$ storage ring and collected by the {\sc BaBar} detector at the SLAC National Accelerator Laboratory. The search is performed using a blind analysis. No significant signal is observed in any of the decay modes, and upper limits are set on the various branching fractions at the 90\% confidence level.