Nonfactorizable charming loops in FCNC B decays versus B -decay semileptonic form factors

We compare a nonfactorizable charming-loop correction to an exclusive FCNC B decay given in terms of the three-particle Bethe-Salpeter amplitude (3BS) of the B meson, «0|q¯(x)Gμν(z)b(0)|B(p)», with the corresponding correction to the B-meson semileptonic form factor. In spite of certain similarities, these two corrections are shown to have substantial differences: the form-factor correction is dominated by the collinear light-cone configuration of 3BS (zμ=uxμ, 0<u<1, x2=0); in contrast, the FCNC amplitude is dominated by a different configuration with noncollinear arguments [x2=0, z2=0, but (x-z)2≠0 (i.e., zμ≠uxμ)].