Analysis of B ->phi K decays in QCD factorization - art. no. 074004

We analyze the decay B --> phiK within the framework of QCD-improved factor ization. We find that although the twist-3 kaon distribution amplitude domi nates the spectator interactions, it will suppress the decay rates slightly . The weak annihilation diagrams induced by (S-P)(S+P) penguin operators, w hich are formally power suppressed by order (A(QCD)/m(b))2, are chirally an d logarithmically enhanced. Therefore, these annihilation contributions are not subject to helicity suppression and can be sizable. The predicted bran ching ratio of B---> phiK(-) is (3.8 +/- 0.6) x 10(-6) in the absence of an nihilation contributions, and it becomes (43(-1.4)(+3.0)) x 10(-6) when ann ihilation effects are taken into account. The prediction is consistent with the experimental data.