ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2012, vol. 108, p. -
Evidence for direct CP violation in B ±→ηh ± and observation of B0→ηK0
We report measurements of the branching fractions and CP asymmetries for B ±→ηh ± (h=K or π) and the observation of the decay B0→ηK0 from the final data sample of 772×106BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e +e - collider. The measured branching fractions are B(B ±→ηK ±)=(2. 12±0.23±0.11)×10 -6, B(B ±→ηπ ±)=(4.07±0. 26±0.21)×10 -6, and B(B0→ηK0)=(1.27-0.29+0. 33±0.08)×10 -6, where the last decay is observed for the first time with a significance of 5.4 standard deviations (σ). We also find evidence for CP violation in the charged B modes, A CP(B ±→ηK ±)=-0.38±0.11±0. 01 and A CP(B ±→ηπ ±)=- 0.19±0.06±0.01 with significances of 3.8σ and 3.0σ, respectively. For all measurements, the first and second uncertainties are statistical and systematic, respectively. © 2012 American Physical Society.