QCD factorization for exclusive non-leptonic B-meson decays: General arguments and the case of heavy-light final states

We provide a rigorous basis for factorization for a large class of non-leptonic two-body B-meson decays in the heavy-quark limit. The resulting factorization formula incorporates elements of the naive factorization approach and the hard-scattering approach, but allows us to compute systematically radiative ("non-factorizable") corrections to naive factorization for decays such as B→Dπ and B→ππ. We first discuss the factorization formula from a general point of view. We then consider factorization for decays into heavy-light final states (such as B→Dπ) in more detail, including a proof of the factorization formula at two-loop order. Explicit results for the leading QCD corrections to factorization are presented and compared to existing measurements of branching fractions and final-state interaction phases.