Revisiting nonfactorizable charm-loop effects in exclusive FCNC B-decays.

Abstract We revisit the calculation of nonfactorizable corrections induced by charm-quark loops in exclusive FCNC B -decays. For the sake of clarity, we make use of a field theory with scalar particles: this allows us to focus on the conceptual issues and to avoid technical complications related to particle spins in QCD. We perform a straightforward calculation of the appropriate correlation function and show that it requires the knowledge of the full generic three-particle distribution amplitude with non-aligned arguments, 〈 0 | s ¯ (y) G μ ν (x) b (0) | B (p) 〉. Moreover, the dependence of this quantity on the variable (x − y) 2 is essential for a proper account of the (Λ QCD m b / m c 2) n terms in the amplitudes of FCNC B -decays. [ABSTRACT FROM AUTHOR]