Improved Measurements of Direct CP Violation in B --> K+pi-, K+pi0 and pi+pi0 Decays

Abstract

We report an improved measurement of direct CP violation in the decay B0 --> K+pi-, and a search for CP violation in the decays B+ --> K+pi0 and B+ --> pi+pi0. The measured CP violating asymmetries are Acp(K+pi-)=-0.113+-0.022(stat.)+-0.008(syst.), Acp(K+pi0)=0.04+-0.04(stat.)+-0.02(syst.) and Acp(pi+pi0)=0.02+-0.08(stat.)+-0.01(syst.), where the latter correspond to the intervals -0.03<Acp(K+pi0)<0.11 and -0.12<Acp(pi+pi0)<0.15 at 90% confidence level. These results are obtained from a data sample that contains 386 million BBbar pairs that was collected near the Y(4S) resonance, with the Belle detector at the KEKB asymmetric nergy e+e- collider. All of the results are preliminary.