A Precision Method for Determining γ from B->ππ Decays

Factorization based on the soft-collinear effective theory reduces the number of hadronic parameters in an isospin analysis of B->ππ decays by one. Using the available B->ππ data allows us to simultaneously fit for these hadronic parameters and obtain a precise value of the CP violating phase γ, namely γ=74-16-9-bar -bar +9+2-bar . The first uncertainties are experimental and the second are theoretical and dominated by power corrections to our analysis. The theory error is lopsided because SCET predicts that γ lies close to the upper bound determined by isospin, γ-bar 75.2+/-8.2-bar (where the error here is experimental)