We present results on time-dependent CP asymmetries in neutral B decays. 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 B0or [Formula: see text] from its decay products. Using data collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC, we measure sin 2β = 0.722 ± 0.040( stat ) ± 0.023( syst ) and [Formula: see text], determining the sign of cos 2β to be positive at 86% CL.
Study of Time-Dependent CP Asymmetry in Neutral B Decays to J/{psi}{pi}{sup 0}