On the nonperturbative charm effects in inclusive B→Xc lν decays

We address the nonperturbative effects associated with soft charm quarks in inclusive B decays. Such corrections are allowed by the OPE, but have largely escaped attention so far. The related four-quark ‘double heavy’ expectation values of the form 〈B|b̄c c̄b|B〉 are computed in the 1/mc expansion by integrating out the charm field to one and two loops. A significant enhancement of the two-loop coefficients has been noted. A method is suggested for evaluating the expectation values of the higher-order b-quark operators required to calculate charm expectation values, free from the overly large ambiguities of dimensional analyses. The soft-charm effects were found generally at the level of 0.5% in Γsl(b→ c); however, as a result of cancellations the net impact should be smaller. We propose a direct way to search for such effects in the data. Finally, we discuss the relation of the soft charm corrections in inclusive decays with the ‘Intrinsic Charm’ ansatz. ∗ On leave of absence from St. Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188300, Russia