Improved measurement of CP-violation in $B \to (c{\bar c})K^{(\ast)0}$ decays

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.

REDUCING THE EXPERIMENTAL UNCERTAINTY ON THE CKM ANGLE α

We investigate possible strategies to reduce the experimental uncertainty on the CKM angle α, in the working conditions of an asymmetric e+ e-B-factory. We propose to use information from the time-dependent asymmetry of neutral B-decays to π+ π-, together with the ratio [Formula: see text]. We also consider the possibility of using information on the ratio [Formula: see text]. An error analysis on α depending on the expected experimental uncertainties on the input quantities is carried out.