| Abstract |
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We present partial branching fractions for inclusive charmless semileptonic B
decays Bbar --> X_u ell nubar, and the determination of the CKM matrix element |V_{ub}|.
The analysis is based on a sample of 383 million Y(4S) decays into B Bbar pairs
collected with the BaBar detector at the PEP-II e+ e- storage rings.
We select events using either the invariant mass M_X of the hadronic system,
the invariant mass squared, q^2, 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:
Delta B = (1.18 +- 0.09_{stat.} +- 0.07_{sys.} +- 0.01_{theo.}) x 10^{-3} (M_X < 1.55 GeV /c^2),
Delta B = (0.95 +- 0.10_{stat.} +- 0.08_{sys.} +- 0.01_{theo.}) x 10^{-3} (P_{+} < 0.66 GeV /c ), and
Delta B = (0.76 +- 0.08_{stat.} +- 0.07_{sys.} +- 0.02_{theo.}) x 10^{-3} (M_X < 1.7 GeV/c^2, q^2 > 8 GeV^2 / c^4).
Corresponding values of |V_{ub}| are extracted using several theoretical calculations.
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