Threshold resummation for nonleptonic B meson decays
  We investigate the double logarithmic corrections $\alpha_s\ln^2 x$, x being a parton momentum fraction, in two-body nonleptonic B meson decays in collinear factorization theorem of perturbative QCD (PQCD). It is found that these corrections are universal for factorizable amplitudes, {\it i.e.}, at the leading power, and that their threshold resummation smears the end-point singularities from $x\to 0$. The double logarithmic corrections, depending on the topologies of nonfactorizable amplitudes at the subleading power, are negligible due to the color-transparency argument and to the overlap of three meson distribution amplitudes. We show that the PQCD approach to two-body nonleptonic B meson decays respects the factorization assumption in the heavy-quark limit. 
Hsiang-nan Li, Kazumasa Ukai