Measurements of branching fractions and directCPasymmetries forB→Kπ,B→ππandB→KKdecays

Abstract

We report measurements of the branching fractions and direct CP asymmetries (ACP) for B→Kπ, ππ and KK decays (but not π0π0) based on the final data sample of 772×106 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We set a 90% confidence-level upper limit for K+K− at 2.0×10−7; all other decays are observed with branching fractions ranging from 10−6 to 10−5. In the B0/B¯0→K±π∓ mode, we confirm Belle’s previously reported large ACP with a value of −0.069±0.014±0.007 and a significance of 4.4σ. For all other flavor-specific modes, we find ACP values consistent with zero, including ACP(K+π0)=+0.043±0.024±0.007 with 1.8σ significance. The difference of CP asymmetry between B±→K±π0 and B0/B¯0→K±π∓ is found to be ΔAKπ≡ACP(K+π0)−ACP(K+π−)=+0.112±0.027±0.007 with 4.0σ significance. We also calculate the ratios of partial widths for the B→Kπ decays. Using our results, we test the validity of the sum rule ACP(K+π−)+ACP(K0π+)Γ(K0π+)Γ(K+π−)−ACP(K+π0)2Γ(K+π0)Γ(K+π−)−ACP(K0π0)2Γ(K0π0)Γ(K+π−)=0 and obtain a sum of −0.270±0.132±0.060 with 1.9σ significance.Received 4 October 2012DOI:https://doi.org/10.1103/PhysRevD.87.031103© 2013 American Physical Society