Measurement of the inclusive electron spectrum from B meson decays and determination of |V[subscript ub]|

Abstract

Based on the full BABAR data sample of 466.5 million B[bar over B] 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[subscript u]eν decays from the CKM-favored B→X[subscript c]eν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B(B→X[subscript eν])=(10.34±0.04[subscript stat]±0.26[subscript syst])%, averaged over B[superscript ±] and B[superscript 0] mesons. We determine the spectrum and branching fraction for charmless B→X[subscript u]eν decays and extract the CKM element |V[subscript 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[subscript ub]| are presented, with the lower limit on the electron momentum varied from 0.8 GeV/c to the kinematic endpoint. We determine |V[subscript ub]| using each of these different calculations and find, |V[subscript ub]|=(3.794±0.107[subscript exp] [subscript -0.219 SF][superscript +0.292] [subscript -0.068 theory][superscript +0.078])×10[superscript -3] (De Fazio and Neubert), (4.563±0.126[subscript exp][subscript -0.208 SF][superscript +0.230] [subscript -0.163 theory][superscript +0.162])×10[superscript -3] (Bosch, Lange, Neubert, and Paz), (3.959±0.104[subscript exp][subscript -0.154 SF][superscript +0.164][subscript -0.079 theory][superscript +0.042])×10[superscript -3] (Gambino, Giordano, Ossola, and Uraltsev), (3.848±0.108[superscript exp][subscript -0.070 theory][superscript +0.084])×10[superscript -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.