Evidence for Direct CP Violation in B0→K+π-Decays

We report evidence for direct CP violation in the decay B⁰→K⁺π^- with 253 fb^-1 of data collected with the Belle detector at the KEKB e⁺e^- collider. Using 275×10⁶ BB¯ pairs we observe a B→K^±π^∓ signal with 2140±53 events. The measured CP violating asymmetry is A_CP(K⁺π^-)=-0.101±0.025(stat)±0.005(syst), corresponding to a significance of 3.9σ including systematics. We also search for CP violation in the decays B⁺→K⁺π⁰ and B⁺→π⁺π⁰. The measured CP violating asymmetries are A_CP(K⁺π⁰)=0.04±0.05(stat)±0.02(syst) and A_CP(π⁺π⁰)=-0.02±0.10(stat)±0.01(syst), corresponding to the intervals -0.05<A_CP(K⁺π⁰)<0.13 and -0.18<A_CP(π⁺π⁰)<0.14 at 90% confidence level.