Branching fraction and form-factor shape measurements of exclusive charmless semileptonicBdecays, and determination of|Vub|

Abstract

Kerth, L. et al.. (2012) Branching fraction and form-factor shape measurements of exclusive charmless semileptonic B decays, and determination of |V_{ub}|. Physical Review D (Particles, Fields, Gravitation and Cosmology), Vol.86 (No.9). Article no.092004 Permanent WRAP url: http://wrap.warwick.ac.uk/52210 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes the work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement: © 2012 American Physical Society A note on versions:The version presented here is a working paper or pre-print that may be later published elsewhere. If a published version is known of, the above WRAP url will contain details on finding it. We report the results of a study of the exclusive charmless semileptonic decays,undertaken with approximately 462 × 10 6 BB pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of q 2 , the square of the momentum transferred to the lepton-neutrino pair, for B 0 → π − ℓ + ν, B + → π 0 ℓ + ν, B + → ωℓ + ν and B + → ηℓ + ν. From these distributions, we extract the form-factor shapes f+(q 2 ) and the total branching fractions B(B 0 → π − ℓ + ν) = (1.45 ± 0.04stat ± 0.06syst) × 10 −4 (combined π − and π 0 decay channels assuming isospin symmetry), B(B + → ωℓ + ν) = (1.19 ± 0.16stat ± 0.09syst) × 10 −4and B(B + → ηℓ + ν) = (0.38 ± 0.05stat ± 0.05syst) × 10 −4 . We also measure B(B + → η ′ ℓ + ν) = (0.24 ± 0.08stat ± 0.03syst) × 10 −4 . We obtain values for the magnitude of the CKM matrix element |V ub | by direct comparison with three different QCD calculations in restricted q 2 ranges of B → πℓ + ν decays. From a simultaneous fit to the experimental data over the full q 2 range and the FNAL/MILC lattice QCD predictions, we obtain |V ub | = (3.25 ± 0.31) × 10 −3 , where the error is the combined experimental and theoretical uncertainty.

B →Vℓ+ℓ− in the Standard Model from light-cone sum rules

“…The most recent measurements of the branching ratios have been performed for B → ρ ν by BaBar [87] and Belle [88] and for B → ω ν by BaBar [89,90] and Belle [88] respectively. We extract |V ub | from the BaBar and Belle data by minimizing the χ 2 function that reads in both cases 20) where B i exp and B i th are the experimental and theoretical central values for the branching ratios in one q 2 -bin and the sum runs over all bins for the charged and neutral mode.…”

Semileptonic B decays

“…The most recent BaBar estimate from exclusive decays yields |V ub | = (3.25 ± 0.31) × 10 −3 [43] and it is determined from the simultaneous fit to the experimental data and the lattice theoretical predictions. It is compatible with the Belle result [44] of |V ub | = (3.43 ± 0.33) × 10 −3 .…”

Determination of the quark coupling strength |Vub| using baryonic decays

“…The world average from ref. 7 for this method, using the decays B 0 → π + − ν and B − → π 0 − ν, is |V ub | = (3.28 ± 0.29) × 10 −3 , where the most precise experimental inputs come from the BaBar 8,9 and Belle 10,11 experiments. The uncertainty is dominated by the LQCD calculations, which have recently been updated 12,13 and result in larger values of V ub than the average given in ref.…”