Spectra of prompt electrons from decays of B+ and B0 mesons and ratio of inclusive semielectronic branching fractions

TL;DR

This paper measures the spectra of prompt electrons from B+ and B0 meson decays and determines the ratio of their inclusive semileptonic branching fractions using data from the Belle detector at KEKB.

Contribution

It provides the first measurement of the electron spectra from B meson decays and the ratio of their semileptonic branching fractions with improved precision.

Findings

Ratio of semileptonic branching fractions b_+/b_0 = 1.08 ± 0.05 ± 0.02

Electron spectra from B meson decays measured for the first time

Partial decay rates for electrons with momentum > 0.6 GeV/c obtained

Abstract

We present spectra of prompt electrons from decays of neutral and charged B mesons. The results are based on 140 /fb of data collected by the Belle detector on the Upsilon(4S) resonance at the KEKB e+e- asymmetric collider. We tag Upsilon(4S) -> B \bar{B} events by reconstructing a B meson in one of several hadronic decay modes; the semileptonic decay of the other B meson is inferred from the presence of an identified electron. We obtain for charged and neutral B mesons the partial rates of semileptonic decay, to electrons with momentum greater than 0.6 GeV/c in the B rest frame, and their ratio b_+/b_0 = 1.08 +- 0.05 +- 0.02, where the first and second errors are statistical and systematic, respectively.