Improved Measurement ofCPAsymmetries inB0→(cc¯)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 million $\Upsilon$(4S) $\rightarrow B\overline{B}$ decays collected by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. The amplitude of the CP asymmetry, sin2$\Beta$ 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 $B^0$ or $\overline{B}^0$ from its decay products. We measure sin2$\Beta$ = 0.722 $\pm$ 0.040 (stat.) $\pm$ 0.23 (syst.) in agreement with the Standard Model expectation.