Spectator effects in inclusive decays of beauty hadrons

We present a model-independent study of spectator effects, which are responsible for the lifetime differences between beauty hadrons. These effects can be parametrized in terms of hadronic matrix elements of four four-quark operators. For B mesons, the coefficients of the non-factorizable operators turn out to be a factor 10--100 larger than those of the factorizable ones, and so the vacuum insertion approximation cannot be trusted. Theoretically, the deviation of \tau(B^-)/\tau(B_d) from unity could be as large as 20\%, and even the sign of this deviation cannot be predicted at present. In the case of the \Lambda_b baryon, heavy-quark symmetry is used to reduce the number of independent matrix elements from four to two. In order to explain the large deviation from unity in the experimental result for \tau(\Lambda_b)/\tau(B_d), it is necessary that these baryon matrix elements be much larger than those estimated in quark models. We also study spectator effects in the semi-leptonic branching ratio of B mesons and find that they could conceivably lower B_{\rm SL} by up to 1\%.