We present a measurement of the standard model CP violation parameter sin2ϕ1 based on a 29.1 fb−1 data sample collected at the γ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. One neutral B meson is fully reconstructed as a J/ψKS, ψ(2S)KS, χc1KS, ηcKS, J/ψKL, or J/ψK*0 decay and the flavor of the accompanying B meson is identified from its decay products. From the asymmetry in the distribution of the time intervals between the two B meson decay points, we determine sin2ϕ1=0.99±0.14(stat)±0.06(syst). We conclude that we have observed CP violation in the neutral B meson system.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)