Nonfactorizable charming loops in FCNC <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> decays versus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>B</mml:mi></mml:math> -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) meson, $⟨0|\overline{q}(x){G}_{\ensuremath{\mu}\ensuremath{\nu}}(z)b(0)|B(p)⟩$, with corresponding $B$-meson semileptonic form factor. In spite certain similarities, these two corrections are shown have substantial differences: form-factor is dominated by collinear light-cone configuration 3BS (${z}_{\ensuremath{\mu}}=u{x}_{\ensuremath{\mu}}$, $0&lt;u&lt;1$, ${x}^{2}=0$); contrast, different noncollinear arguments [${x}^{2}=0$, ${z}^{2}=0$, but $(x\ensuremath{-}z{)}^{2}\ensuremath{\ne}0$ (i.e., ${z}_{\ensuremath{\mu}}\ensuremath{\ne}u{x}_{\ensuremath{\mu}}$)].