Observation of time-dependent CP violation in B0→η′K0 decays and improved measurements of CP asymmetries in B0→φK0, KS0KS0KS0 and B0→J/ψK0 decays

We present improved measurements of CP-violation parameters in B-0 -> phi K-0, eta K-'(0), (KSKSKS0)-K-0-K-0 decays based on a sample of 535 x 10(6) B (B) over bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We obtain sin2 phi(eff)(1) = +0.64 +/- 0.10(stat) +/- 0.04(syst) for B-0 -> eta K-'(0), +0.50 +/- 0.21(stat) +/- 0.06(syst) for B-0 ->phi K-0, and +0.30 +/- 0.32(stat) +/- 0.08(syst) for B-0 -> (KSKSKS0)-K-0-K-0 decays. We have observed CP violation in the B-0 -> eta K-'(0) decay with a significance of 5.6 standard deviations. We also perform an improved measurement of CP asymmetries in B-0 -> J/psi K-0 decays and obtain sin2 phi(1) = +0.642 +/- 0.031(stat) +/- 0.017(syst).