Revisiting the annihilation decay $\bar{B}_{s} \to \pi^+\pi^{-}$

It is very important to know the strength of the annihilation contribution in B charmless non-leptonic decays. The B/sub s /macronrightward arrowpi/sup positive pi; /sup negative process could serve as a good probe of the strength. We have studied the process in the QCD factorization framework. Using a gluon mass scale dictated by the studies of infrared behavior of gluon propagators to avoid enhancements in the soft endpoint regions, we find that the CP averaged branching ratio is about 1.24?0/sup -7/, the direct CP asymmetry C/sub pipi/ is about -0.05, while the mixing-induced CP asymmetry is quite large with the value S/sub pipi/=0.18. This process could be measured at LHC-b experiments in the near future and would deepen our understanding of the dynamics of B charmless decays.