We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88×106 Υ(4S)→BB̅ decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We study 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. The amplitude of the CP asymmetry, which in the standard model is proportional to sin2β, is derived from the decay-time distributions in such events. We measure sin2β=0.741±0.067(stat)±0.034(syst) and |λ|=0.948±0.051(stat)±0.030(syst). The magnitude of λ is consistent with unity, in agreement with the standard model expectation of no direct CP violation in these modes.
File in questo prodotto:
Non ci sono file associati a questo prodotto.