Branching ratio and CP violation of B ->pi pi decays in the perturbative QCD approach - art. no. 074009

We calculate the branching ratios and CP asymmetries for B-o -->pi (+)pi (- ), B+-->pi (+)pi (o), and B-o --> pi (o)pi (o) decays. in a perturbative QC D approach. In this approach, we calculate nonfactorizable and annihilation type contributions, in addition to the usual factorizable contributions. W e find that the annihilation diagram contributions are not very small as pr eviously argued. Our result is in agreement with the measured branching rat io of B --> pi (+)pi (-) by the CLEO Collaboration. With a non-negligible c ontribution from annihilation diagrams and a large strong phase, we predict a large direct CP asymmetry in B-o --> pi (+)pi (-), and pi (o)pi (o), whi ch can be tested by the current running B factories.