Measurement of CP Asymmetries and Branching Fractions in B -> pi pi and B -> K pi decays

We present preliminary measurements of the CP asymmetries and branching fractions for B -> pi pi and B -> K pi decays. A total of 347 million BBbar events collected by the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC are used for these results. We find Spipi = -0.53 +- 0.14 +-0.02, Cpipi = -0.16 +- 0.11 +- 0.03, AKpi = -0.108 +- 0.024 +- 0.008, BF(B0 -> pi0 pi0) = (1.48 +- 0.26 +- 0.12) x 10^-6, BF(B+ -> pi+pi0) = (5.12 +- 0.47 +- 0.29) x 10^-6, BF(B+ -> K+pi0) = (13.3 +- 0.56 +- 0.64) x 10^-6, Cpi0pi0 = -0.33 +- 0.36 +- 0.08, Apipi0 = -0.019 +- 0.088 +- 0.014, AKpi0 = 0.016 +- 0.041 +- 0.012. The measured values of Spipi and Cpipi imply that CP conservation in B0 -> pi+ pi- decays is excluded at the 3.6 sigma level. From these results we present bounds on the CKM angle alpha.