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 ! + decay channel employing the per- turbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sucien tly considered, we constrain the UT angle to 53 6 6 70 , from the measurements of the CP violation parameters C + and S + in B 0 ! + . The U-spin breaking eect between B 0 ! + and B 0 ! K + K is estimated to be around 30%.