Measurements of the Partial Branching Fraction for B->Xulnu and the Determination of Vub

Understand

We measure partial branching fractions for the inclusive charmless semileptonic decay of $\Bxulnu$, and present determinations of the CKM matrix element $\Vub$.

• This analysis is based on a sample of 467 million $\FourS$ decays into $\BB$ pairs, collected with the \babar\ detector at the PEP-II $e^{+} e^{-}$ storage rings.
• We select events where one of the B mesons is fully reconstructed in a hadronic decay mode and the other B decays semileptonically into an electron or a muon.
• We then use the invariant mass, $\mx$, of the hadronic system, the invariant mass squared, $q^{2}$, of the lepton and neutrino pair, the lepton momentum in the in the $B$ meson rest frame $\Pl$, the kinematic variable $P_{+}$ or one of their combinations as discriminating variables to isolate $\Bxulnu$ decays from the background.