NONPERTURBATIVE CORRECTIONS TO INCLUSIVE BEAUTY AND CHARM DECAYS - QCD VERSUS PHENOMENOLOGICAL MODELS

We present a self-consistent method for treating nonperturbative effects in inclusive nonleptonic and semileptonic decays of heavy flavour hadrons. These effects give rise to powertike corrections is-proportional-to 1/m(Q)n with n greater-than-or-equal-to 2. The leading correction to the semileptonic branching ratio occurs for n = 2. It is expressed in terms of the vector-pseudoscalar mass splitting: sigmaBR(sl)/BR(sl) almost-equal-to BR(nl) 6 [(M(V)2-M(P)2)/m(Q)2] (C+2 - C-2)/2N(c) and yields a reduction of BR(sl). This nonperturbative correction contributes to the nonleptonic width with a sign opposite to that of the perturbative terms that are non-leading in 1/N(c) beauty decays the former reduces the latter by 20% whereas in charm decays they more or less cancel. This leads to a reduction of BR(sl) by no more than 10% in beauty decays and by a factor of roughly two in charm decays. Phenomenological models of heavy flavour decays are unable to mimic these leading corrections by a specific choice of quark masses or by invoking Fermi motion.