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Published April 1, 2017 | Submitted + Published
Journal Article Open

Measurement of the inclusive electron spectrum from B meson decays and determination of │V_(ub)│


Based on the full BABAR data sample of 466.5 million BB pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X_ueν decays from the CKM-favored B → X_ceν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B(B → Xeν) = (10.34 ± 0.04_(stat) ± 0.26_(syst) %, averaged over B^± and B^0 mesons. We determine the spectrum and branching fraction for charmless B → X_ueν decays and extract the CKM element |V_ub|, by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV/c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V_ub| are presented, with the lower limit on the electron momentum varied from 0.8  GeV/c to the kinematic endpoint. We determine |V_ub| using each of these different calculations and find, |V_ub|= (3.794 ± 0.107_(exp) ^(+0.292)_(−0.219) SF ^(+0.078) _(−0.068) theory) × 10^(−3) (De Fazio and Neubert), (4.563 ± 0.126_(exp) ^(+0.230)_(−0.208) SF ^(+0.162) _(−0.163) theory) × 10^(−3) (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104_(exp)^(+0.164)_(−0.154) SF ^(+0.042) _(−0.079) theory) × 10^(−3) (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108_(exp)^(+0.084)_^(−0.070) theory) × 10^(−3) (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.

Additional Information

© 2017 American Physical Society. Received 22 November 2016; published 5 April 2017. We thank S. W. Bosch, B. O. Lange, M. Neubert, and G. Paz, and similarly P. Gambino, P. Giordano, G. Ossola, and N. Uraltsev, for providing the software to implement their respective calculations. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relies critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. This work is supported by the U.S. Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat à l'Energie Atomique and Institut National de Physique Nucléaire et de Physique des Particules (France), the Bundesministerium für Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (The Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Economía y Competitividad (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation (USA).

Attached Files

Published - PhysRevD.95.072001.pdf

Submitted - 1611.05624.pdf


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