The Semileptonic Decay Fraction of B-Mesons in the Light of Interfering Amplitudes

Consequences of the interference between spectator amplitudes for the lifetimes and semileptonic decay fractions of B and B mesons are discussed. Extracting these amplitudes from a fit to 11 exclusive hadronic B decay fractions we find a1 = 1.05 ± 0.03 ± 0.10, a2 = +0.227 ± 0.012 ± 0.022, an inclusive semileptonic decay fraction of (11.2 ± 0.5 ± 1.7)%, and a lifetime ratio τ(B)/τ(B) = 0.83± 0.01± 0.01. Although there has been significant progress in the calculation of QCD corrections in the decays of heavy flavour mesons, there are still some unsolved puzzles. One of the most intriguing is the low semileptonic decay fraction of B mesons [1]. We will show in this paper that the discrepancy between theory and experiment is considerably reduced by the interpretation of recent CLEO results [2] on hadronic decay fractions in the framework of the spectator model with factorization. The D-D meson lifetime difference has been satisfactorily reproduced in such a model by Bauer, Stech, and Wirbel [3,4], using interfering amplitudes of spectator diagrams for D hadronic two-body decays. The same model predicts a negligible difference between the decay rates for two body modes of B and B mesons. However, in contrast to the D system, only a small fraction of all hadronic B meson decays is included in the calculation so a conclusive prediction of the lifetime ratio is not possible. Using duality between the quark and the hadron pictures of strong interactions, we will demonstrate 1 Supported under DOE grant number DE-FG02-91-ER40690. 2 Supported by the German Bundesministerium für Forschung und Technologie, under contract number 056DD11P. 1