SPECTATOR EFFECTS IN INCLUSIVE DECAYS OF BEAUTY HADRONS

We present a model-independent study of spectator effects, which are r esponsible for the lifetime differences between beauty hadrons. These effects can be parametrized in terms of hadronic matrix elements of fo ur four-quark operators. For B mesons, the coefficients of the non-fac torizable operators rum out to be much larger than those of the factor izable ones, limiting considerably the usefulness of the vacuum insert ion approximation. Non-factorizable contributions to the lifetime rati o tau(B-)/tau(B-d) could naturally be of order 10-20%, and not even th e sign of these contributions can be predicted at present. In the case of the Lambda(b) baryon, heavy-quark symmetry is used to reduce the n umber of independent matrix elements from four to two. In order to exp lain the large deviation from unity in the experimental result for tau (Lambda(b))/tau(B-d), it is necessary that these baryon matrix element s be much larger than those estimated in quark models. We have also re examined the theoretical predictions for the semileptonic branching ra tio of B mesons and charm counting, finding that, given the present th eoretical and experimental uncertainties, there is no significant disc repancy with experiment.