Improved measurement of CP asymmetries in B0 -> (c c-bar) K0(*) decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227×10^6 Υ(4S)→BB̅ decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CP asymmetry, sin⁡2β in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B0 or B̅ 0 from its decay products. We measure sin⁡2β=0.722±0.040(stat)±0.023(syst) in agreement with the standard model expectation.