Eur. Phys. J. C (2007) 50: 539-556
https://doi.org/10.1140/epjc/s10052-007-0216-8

Regular Article -Theoretical Physics

On the nonperturbative charm effects in inclusive B→X_cℓν decays

¹ Department of Physics, University of Notre Dame du Lac, Notre Dame, IN, 46556, USA
² INFN, Sezione di Milano, Milan, Italy
³ Theory Division, CERN, Geneva, Switzerland
⁴ William Fine Theoretical Physics Institute, University Minnesota, Minneapolis, MN, 55455, USA
⁵ IPPP, Department of Physics, University of Durham, Durham, DH1 3LE, UK

^* e-mail: roman.zwicky@durham.ac.uk

Received: 17 November 2006
Published online: 6 March 2007

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 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 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 Γ_sl(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.