Impact of Four-Quark Shape Functions on Inclusive B Decay Spectra
Abstract
It has recently been pointed out that a new class of subleading shape functions involving B-meson matrix elements of non-local four-quark operators contributes at order LambdaQCD/mb to B->Xu+l+nu decay distributions in the endpoint region. The corresponding functions fu(omega) and fv(omega) are estimated using the vacuum-insertion approximation. A numerical analysis of various B->Xu+l+nu decay spectra suggests that these power corrections are very small, below present theoretical uncertainties due to other subleading shape-function contributions.
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