Abstract
We report new measurements of semileptonic branching fractions of mesons produced at the resonance determined by fitting the inclusive electron and muon momentum spectra to different theoretical models. Using to denote the average of the semileptonic branching fractions for decay to electrons and muons, we obtain using the refined free-quark model of Altarelli et al., and using a modified version of the form-factor model of Isgur et al., in which the contribution is allowed to float in the fit. The average of these two results is , where the errors are statistical, systematic uncertainties in the measurement, and systematic uncertainties associated with the theoretical models, respectively. Semileptonic branching fractions as low as this are difficult to accommodate in theoretical models where hadronic -meson decays arise only from spectator diagrams. We use dilepton yields to limit the uncertainty in the semileptonic branching fraction due to the possible existence of non- decays of the . In addition, we tag neutral mesons using the decays and to obtain the first direct measurement of semileptonic branching fractions for neutral mesons; the average of the electron and muon results for neutral mesons is .
- Received 8 July 1991
DOI:https://doi.org/10.1103/PhysRevD.45.2212
©1992 American Physical Society