Analysis of B → φK Decays in QCD Factorization

We analyze the decay B → φK within the framework of QCD-improved factorization. We found that although the twist-3 kaon distribution amplitude dominates the spectator interactions, it will suppress the decay rates slightly. The weak annihilation diagrams induced by (V −A)(V +A) penguin operators, which are formally power-suppressed by order (ΛQCD/mb) 2, are chirally and in particular logarithmically enhanced. Therefore, these annihilation contributions are not subject to helicity suppression and can be sizable. The predicted branching ratio of B → φK is of order (0.7 ∼ 1.1) × 10−5 if the phase of the annihilation amplitude lies in the range 45◦ < θ < 90◦. The corresponding absolute ratio of annihilation to penguin amplitudes is about 0.4 ∼ 0.5 .