Improved measurement of mixing-induced CP violation in the neutral B meson system -: art. no. 071102

We present an improved measurement of the standard model CP violation parameter sin 2phi(1) (also known as sin 2beta) based on a sample of 85x10(6) B (B) over bar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. One neutral B meson is reconstructed in a J/psiK(S)(0), psi(2S)K(S)(0), chi(c1)K(S)(0), eta(c)K(S)(0), J/psiK*(0), or J/psiK(L)(0) CP-eigenstate decay channel and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time interval between the two B meson decay points, we obtain sin 2phi(1)=0.719+/-0.074(stat)+/-0.035(syst).