Measurement of time-dependent CP violation in B 0 → η'K 0 decays

We present a measurement of the time-dependent CP violation parameters in B0 → η'K0 decays. The measurement is based on the full data sample containing 772×106 BB-bar pairs collected at the Υ(4S) resonance using the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values of the mixing-induced and direct CP violation parameters are: sin 2φ1eff = +0.68 ± 0.07 ± 0.03, Aη'K0 = +0.03 ± 0.05 ± 0.04, where the first uncertainty is statistical and the second is systematic. The values obtained are the most accurate to date. Furthermore, these results are consistent with our previous measurements and with the world-average value of sin 2φ1 measured in B0 → J/ψK0 decays.