We have used the CLEO II detector and 2.06fb−1 of ϒ(4S) data to measure the B-meson semileptonic branching fraction. The B → Xeν momentum spectrum was obtained over nearly the full momentum range by using charge and kinematic correlations in events with a high-momentum lepton tag and an additional electron. We find B (B → Xeν) = (10.49 ± 0.17 ± 0.43)%, with overall systematic uncertainties less than those of untagged single-lepton measurements. We use this result to calculate the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element Vcb and to set an upper limit on the fraction of ϒ(4S) decays to final states other than BB¯.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)