Measurements of partial branching fractions for B̄→Xulν̄ and determination of |Vub|

Abstract

We present partial branching fractions for inclusive charmless semileptonic B decays B̄→Xu ν̄, and the determination of the Cabibbo-Kobayashi-Maskawa matrix element |Vub|. The analysis is based on a sample of 383×106 Υ(4S) decays into BB̄ pairs collected with the BABAR detector at the SLAC PEP-II e+e- storage rings. We select events using the invariant mass MX of the hadronic system, the invariant mass squared, q2, of the lepton and neutrino pair, the kinematic variable P+, or one of their combinations. We then determine partial branching fractions in limited regions of phase space: ΔB=(1.18±0.09stat±0.07syst±0.01theor) ×10-3 (MX<1.55GeV/c2), ΔB=(0.95±0.10stat±0. 08syst±0.01theor)×10-3 (P+<0.66GeV/c), and ΔB=(0. 81±0.08stat±0.07syst±0.02theor)×10-3 (MX<1.7GeV/c2, q2>8GeV2/c4). Corresponding values of |Vub| are extracted using several theoretical calculations. © 2008 The American Physical Society.