Search for B̄→Λ_c⁺Xℓ⁻ν̅_ℓ decays in Events with a Fully Reconstructed B Meson

We present a search for semileptonic B decays to the charmed baryon Λc+ based on 420fb -1 of data collected at the Υ(4S) 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 B0 mixing. We obtain a 90% confidence level upper limit of B(B̄→Λc+X -ν ̄)/B(B̄→Λc+X)<3.5%. © 2012 American Physical Society.