Shape Function Effects in B -> X_c l \nu_l
Abstract
Owing to the fact that m_c^2 ~ m_b \Lambda_QCD, the endpoint region of the charged lepton energy spectrum in the inclusive decay B -> X_c l \nu_l is affected by the Fermi motion of the initial-state b quark bound in the B meson. This effect is described in QCD by shape functions. Including the mass of the final-state quark, we find that a different set of operators as employed in Ref. hep-ph/0205150 is needed for a consistent matching, when incorporating the subleading contributions in B -> X_q l \nu_l for both q = u and q = c. In addition, we modify the usual twist expansion in such a way that it yields a description of the lepton energy spectrum which is not just valid in the endpoint region, but over the entire phase space.
Cite
@article{arxiv.hep-ph/0408273,
title = {Shape Function Effects in B -> X_c l \nu_l},
author = {Thomas Mannel and Frank J. Tackmann},
journal= {arXiv preprint arXiv:hep-ph/0408273},
year = {2009}
}
Comments
8 Pages, LaTeX, 2 figures; a few typos corrected and some clarifications added, final journal version