Shape Functions from B -> X_c \ell ν

Abstract

We study inclusive semi-leptonic (B -> X_c \ell ν) decay using the power counting m_c ~ \sqrt{Lambda_{QCD} m_b}. Assuming this scaling for the charm-quark mass, the decay kinematics can be chosen to access the shape-function region even in b -> c transitions. To apply effective field theory methods in this region we extend SCET to describe massive collinear quarks. We calculate the tree-level decay rate, including O(Lambda_{QCD}/m_b) power corrections, and show that it factorizes into a convolution of jet and shape functions. We identify a certain kinematical variable whose decay spectrum is proportional to the universal leading-order shape function familiar from b -> u decay, and speculate as to whether information about this shape function can be extracted from data on b -> c decay.

18 pages, 1 figure, version to appear in PRD

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Cited by in corpus (6)

• Perturbative corrections to $B\to D$ form factors in QCD
• Shape-Function Effects and Split Matching in B-> Xs l+ l-
• Role of "Intrinsic Charm" in Semi-Leptonic B-Meson Decays
• Can $B->X_c\ell \nu$ help us extract |V_{ub}| ?
• NNLO corrections to B --> X_u l nu and the determination of |V_ub|
• Twistor-inspired construction of massive quark amplitudes