Nonfactorizable contributions to B → D^(*) M decays

While the naive factorization assumption works well for many two-body nonleptonic B meson decay modes, the recent measurement of B^↔ → D^(*)0M⁰ with M = π, p, and u shows a large deviation from this assumption. We analyze the B→ D^(*) M decays in the perturbative QCD approach based on the k_T factorization theorem, in which both factorizable and nonfactorizable contributions can be calculated in the same framework. Our predictions for the Bauer-Stech-Wirbel parameters, |a₂/a₁|=0.43 ± 0.04 and Arg(a ₂/a₁)∼-42° and |a₂/a₁| = 0.47±0.05and Arg(a₂/a₁)∼-41°, are consistent with the observed B → D π and B → D*π branching ratios, respectively. It is found that the large magnitude \a₂\ and the large relative phase between a₂ and a₁ come from color-suppressed nonfactorizable amplitudes. Our predictions for the B ^↔0 → D*⁰ρ⁰, D*⁰ω branching ratios can be confronted with future experimental data.