摘要
We study the unexpectedly large rate for the factorization-forbidden decay B →xcoK within the QCD factorization approach. We use a non-zero gluon mass to regularize the infrared divergences in vertex corrections. The end-point singularities arising from spectator corrections are regularized and carefully estimated by the off-shellness of quarks. We find that the contributions arising from the vertex and leading-twist spectator corrections are numerically small, and the twist-3 spectator contribution with chiral enhancement and linear end-point singularity becomes dominant. With reasonable choices for the parameters, the branching ratio for B → XcoK decay is estimated to be in the range （2 ～ 4）× 10^-4, which is compatible with the Belle and BaBar data.
基金
The project supported in part by National Natural Science Foundation of China under Grant Nos. 10421503, 10675003 and the Key Grant Project of Ministry of Education under Grant No. 305001
