Observation of Time-Dependent CP Violation in B~0 → η'K~0 Decays and Improved Measurements of CP Asymmetries in B~0 → φK~0, K_S~0K_S~0K_S~0 and B~0 → J/ψK~0 Decays

摘要

We present improved measurements of CP-violation parameters in B~0 → φK~0, η'K~0, K_S~0K_S~0K_S~0 decays based on a sample of 535 X 10~6 BB pairs collected at the Y(4S) resonance with the Belle detector at the KEKB energy-asymmetric e~+e~- collider. We obtain sin2φ_1~(eff) = +0.64 ± 0.10(stat) ± 0.04(syst) for B~0 → η'K~0, +0.50 ± 0.21(stat) ± 0.06(syst) for B~0 → φK~0, and +0.30 ± 0.32(stat) ± 0.08(syst) for B~0 → K_S~0K_S~0K_S~0 decays. We have observed CP violation in the B~0 → η'K~0 decay with a significance of 5.6 standard deviations. We also perform an improved measurement of CP asymmetries in B~0 → J/ψK~0 decays and obtain sin2φ_1 = +0.642 ± 0.031(stat) ± 0.017(syst).