Observation of CP violation in B0→K+π- and B0→π+π-

Abstract

We report observations of CP violation in the decays B0→K+π- and B0→π+π- in a sample of 383×106 Υ(4S)→BB̄ events. We find 4372±82 B0→K+π- decays and measure the direct CP-violating charge asymmetry AKπ=-0.107±0.018(stat)-0.004+0.007(syst) , which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample, we find 1139±49 B0→π+π- decays and measure the CP-violating asymmetries Sππ=-0.60±0.11(stat)±0.03(syst) and Cππ=-0. 21±0.09(stat)±0.02(syst). CP conservation in B0→π+π- (Sππ=Cππ=0) is excluded at a confidence level 1-C.L.=8×10-8, corresponding to 5.4 standard deviations. © 2007 The American Physical Society.