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

Abstract : We 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.
Document type :
Journal articles

http://hal.in2p3.fr/in2p3-00648919
Contributor : Swarna Bassava <>
Submitted on : Tuesday, December 6, 2011 - 3:47:59 PM
Last modification on : Tuesday, December 22, 2020 - 12:40:02 PM

### Citation

P. del Amo Sanchez, J.P. Lees, V. Poireau, V. Tisserand, D. Bernard, et al.. Study of Bbar --> Xu l nubar decays in BBbar events tagged by a fully reconstructed B-meson decay and determination of |V_{ub}|. Physical Review D, American Physical Society, 2012, 86, pp.032004. ⟨10.1103/PhysRevD.86.032004⟩. ⟨in2p3-00648919⟩

Record views