We study the unexpectedly large rate for the factorization-forbidden decay
BβΟc0βK within the QCD factorization approach. We use a non-zero
gluon mass to regularize the infrared divergences in vertex corrections. The
end-point singularities arising from spectator corrections are regularized and
carefully estimated by the off-shellness of quarks. We find that the
contributions arising from the vertex and leading-twist spectator corrections
are numerically small, and the twist-3 spectator contribution with chiral
enhancement and linear end-point singularity becomes dominant. With reasonable
choices for the parameters, the branching ratio for BβΟc0βK decay is
estimated to be in the range (2β4)Γ10β4, which is compatible with
the Belle and BaBar data.Comment: Appendix added; it is emphasized that in the dominant twist-3
spectator corrections the end-point singularity contributions may be
estimated by the off-shellness of the charm quark (by the binding energy in
charmonium) and the gluon (by the transverse momentum of the light quark in
the kaon