On the nonperturbative charm effects in inclusive B -> X_c lνdecays

Abstract

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|\bar{b}c \bar{c}b|B> are computed in the 1/m_c 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 Γ_{sl}(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.

arXiv comment32 pages, LaTeX, 3 figures. Revised: A number of inconsistencies and typos corrected including the $1/m_c^2$ matrix elements. The effect on Γ_sl is estimated about 0.003, not changing the conclusions. A new reference [9] has been added

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