Measurement of the branching fraction and Λ¯ polarization in B0→Λ¯pπ-

We present a measurement of the B0→Λ̅ pπ- branching fraction performed using the BABAR detector at the PEP-II asymmetric e+e- collider. Based on a sample of 467×106 BB̅ pairs we measure B(B0→Λ̅ pπ-)=[3.07±0.31 (stat)±0.23 (syst)]×10-6. The measured differential spectrum as a function of the dibaryon invariant mass m(Λ̅ p) shows a near-threshold enhancement similar to that observed in other baryonic B decays. We study the Λ̅ polarization as a function of Λ̅ energy in the B0 rest frame (EΛ̅ *) and compare it with theoretical expectations of fully longitudinally right-polarized Λ̅ at large EΛ̅ *.