We report a measurement of the inclusive charmless semileptonic branching fraction of B mesons in a sample of 89×10^6 BB̅ events recorded with the BABAR detector at the Υ(4S) resonance. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson. The number of signal events is extracted from the mass distribution of the hadronic system accompanying the lepton and is used to determine the ratio of branching fractions B(B̅ →Xuℓν̅ )/B(B̅ →Xℓν̅ )=[2.06±0.25(stat)±0.23(syst)±0.36(theo)]×10-2. Using the measured branching fraction for inclusive semileptonic B decays, we find B(B̅ →Xuℓν̅ )=[2.24±0.27(stat)±0.26(syst)±0.39(theo)]×10-3 and derive the Cabibbo-Kobayashi-Maskawa matrix element |Vub|=[4.62±0.28(stat)±0.27(syst)±0.48(theo)]×10-3.
Measurement of the Inclusive Charmless Semileptonic Branching Ratio of B Mesons and Determination of |Vub|
MARGONI, MARTINO;SIMONETTO, FRANCO;STROILI, ROBERTO;VOCI, CESARE;SIMI, GABRIELE;
2004
Abstract
We report a measurement of the inclusive charmless semileptonic branching fraction of B mesons in a sample of 89×10^6 BB̅ events recorded with the BABAR detector at the Υ(4S) resonance. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson. The number of signal events is extracted from the mass distribution of the hadronic system accompanying the lepton and is used to determine the ratio of branching fractions B(B̅ →Xuℓν̅ )/B(B̅ →Xℓν̅ )=[2.06±0.25(stat)±0.23(syst)±0.36(theo)]×10-2. Using the measured branching fraction for inclusive semileptonic B decays, we find B(B̅ →Xuℓν̅ )=[2.24±0.27(stat)±0.26(syst)±0.39(theo)]×10-3 and derive the Cabibbo-Kobayashi-Maskawa matrix element |Vub|=[4.62±0.28(stat)±0.27(syst)±0.48(theo)]×10-3.
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