The Crystal Ball Collaboration has measured the energy spectrum of electrons from semileptonic B meson decays at the e+e- storage ring DORIS II. Branching ratios and weak mixing angles of the Kobayashi-Maskawa matrix are determined using several models for the hadronic matrix elements. We obtain the branching ratio for semileptonic. B decays to charmed states BR(B→evXc)=(11.7±0.4±1.0)%. Our result for the corresponding Kobayashi-Maskawa matrix element is |Vcb|=0.052±0.006. The model dependence of both results is included in the error. We have not observed semileptonic B decays to non-charmed mesons. Analyzing the measured electron spectrum above 2.4 GeV, where no b→c decays contribute, we find BR(B→evXu)/BR(B→evXc)<6.5% at the 90% confidence level. This corresponds to an upper limit |Vub/Vcb|<0.21.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)