Moments of the electron energy spectrum and partial branching fraction of $B \to X_c e \nu$ decays at Belle

Abstract

We report a measurement of the inclusive electron energy spectrum for charmed semileptonic decays of B mesons in a 140fb-1 data sample collected at the \Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider. We determine the first four moments of the electron energy spectrum for threshold values of the electron energy between 0.4 and 2.0 GeV. In addition, we provide values of the partial branching fraction (zeroth moment) for the same electron threshold energies, and independent measurements of the B+ and B0 partial branching fractions at 0.4 GeV and 0.6 GeV electron threshold energies. We measure the independent B+ and B^0 partial branching fractions with electron threshold energies of 0.4 GeV to be \Delta \mathcal{B} (B+ -> X_c e \nu)=(10.79 +/- 0.25(stat.) +/- 0.27(sys.))% and \Delta \mathcal{B} (B0 -> X_c e \nu)=(10.09 +/- 0.30(stat.) +/- 0.22(sys.))%. Full correlations between all measurements are evaluated.