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Study of Bbar --> Xu l nubar decays in BBbar events tagged by a fully reconstructed B-meson decay and determination of |V_{ub}|

By P. Del Amo Sanchez, J.P. Lees, V. Poireau, V. Tisserand, D. Bernard, M. Verderi, N. Arnaud, M. Davier, D. Derkach, J. Firmino Da Costa, G. Grosdidier, F. Le Diberder, A. M. Lutz, B. Malaescu, A. Perez, P. Roudeau, M. H. Schune, J. Serrano, V. Sordini, A. Stocchi, L. Wang, G. Wormser, E. Ben-Haim, M. Bomben, G. R. Bonneaud, H. Briand, G. Calderini, J. Chauveau, O. Hamon, Ph. Leruste, G. Marchiori, J. Ocariz, S. Sitt, S. Emery, G. Hamel De Monchenault, G. Vasseur, Ch. Yèche and M. Zito

Abstract

See paper for full list of authors - 25 pages, 8 postscript figures, submitted to PRDWe report measurements of partial branching fractions for inclusive charmless semileptonic B decays Bbar --> Xu l nubar, and the determination of the CKM matrix element |V_{ub}|. The analysis is based on a sample of 467 million Upsilon(4S) --> BBar decays recorded with the BaBar detector at the PEP-II e^+ e^- storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions DeltaB in several restricted regions of phase space and determine the CKM element |V_{ub}| based on four different QCD predictions. For decays with a charged lepton momentum p_l^* > 1.0 GeV in the B meson rest frame, we obtain DeltaB = (1.80 \pm 0.13 (stat.) \pm 0.15 (sys.) \pm 0.02 (theo.)) \times 10^{-3} from a maximum likelihood fit to the two-dimensional mX-q^2 distribution. Here, mX refers to the invariant mass of the final state hadron X and q^2 is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |V_{ub}| = (4.31\pm 0.25 (exp.) \pm 0.16 (theo.)) \times 10^{-3} as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for B^0 and B^- decays and derive a limit on the isospin breaking in Bbar --> Xu l nubar decays

Topics: 13.20.He, 12.15.Hh, 12.38.Qk, 14.40.Nd, [ PHYS.HEXP ] Physics [physics]/High Energy Physics - Experiment [hep-ex]
Publisher: American Physical Society
Year: 2012
DOI identifier: 10.1103/PhysRevD.86.032004
OAI identifier: oai:HAL:in2p3-00648919v1
Provided by: Hal-Diderot
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