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 \(\langle{B}\mid{\bar{b}c\,\bar{c}b}\mid{B}\rangle\) 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 is 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 to be at the level of 0.5% in Γsl(b→c); our literal estimate is somewhat smaller as a result of partial cancellations. 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.
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Bigi, I., Uraltsev, N. & Zwicky, R. On the nonperturbative charm effects in inclusive B→Xcℓν decays. Eur. Phys. J. C 50, 539–556 (2007). https://doi.org/10.1140/epjc/s10052-007-0216-8
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DOI: https://doi.org/10.1140/epjc/s10052-007-0216-8