The BABAR Collaboration BABAR, the detector for the SLAC PEP-II asymmetric e + e − B Factory operating at the Υ (4S) resonance, was designed to allow comprehensive studies of CP -violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and in a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems , VME-and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

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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.

We describe a measurement of the direct CP asymmetry between inclusive b-->s gamma and b-->s gamma decays. This asymmetry is expected to be less than 0.01 in the standard model, but could be enhanced up to about 0.10 by new physics contributions. We use a sample of 89 x 10(6) BB pairs recorded with the BABAR detector at SLAC PEP-II, from which we reconstruct a set of 12 exclusive b-->s gamma final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A(CP)(b-->s gamma)=0.025+/-0.050(stat)+/-0.015(syst), corresponding to an allowed range of -0.06s gamma)<+0.11 at 90% confidence level.

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