A LATTICE STUDY OF SPECTATOR EFFECTS IN INCLUSIVE DECAYS OF B-MESONS

We compute the matrix elements of the operators which contribute to sp ectator effects in inclusive decays of B-mesons. The results agree wel l with estimates based on the vacuum saturation (factorization) hypoth esis. For the ratio of lifetimes of charged and neutral mesons we find tau(B-)/tau(B-d) = 1.03 +/- 0.02 +/- 0.03, where the first error repr esents the uncertainty in our evaluation of the matrix elements, and t he second is an estimate of the uncertainty due to the fact that the W ilson coefficient functions have only been evaluated at tree-level in perturbation theory. This result is in agreement with the experimental measurement. We also discuss the implications of our results for the semileptonic branching ratio and the charm yield. (C) 1998 Elsevier Sc ience B.V.