Search for ¯B → Λ+cXℓ−¯νℓ decays in events with a fully reconstructed B meson

Abstract

We present a search for semileptonic B decays to the charmed baryon Λ + c based on 420 fb − 1 of data collected at the Υ ( 4 S ) resonance with the BABAR detector at the PEP-II e + e − storage rings. By fully reconstructing the recoiling B in a hadronic decay mode, we reduce non- B backgrounds and determine the flavor of the signal B . We statistically correct the flavor for the effect of the B 0 mixing. We obtain a 90% confidence level upper limit of B ( ¯¯¯ B → Λ + c X ℓ − ¯ ν ℓ ) / B ( ¯¯¯ B → Λ + c X ) < 3.5 % .