Constraining the UT angle γ by CP violation parameters in B~0→π~+π~-

We calculate the tree and penguin amplitudes in the B~0→π~+π~-decay channel employing the perturbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sufficiently considered, we constrain the UT angle γ to 53°γ 70°, from the measurements of the CP violation parameters C_(π~+π~-) and S_(π~+π~-)in B~0→π~+π~-. The U-spin breaking effect between B~0→π~+π~-and B~0 s →K~+K~-is estimated to be around 30%.