We report on measurements of time-dependent CP-violation parameters in neutral B meson systems based on a 140fb -1 data sample collected at the ϒ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e+e- collider. One B meson is fully reconstructed in one of the CP eigenstate decay channels, and its flavor is identified from the decay products of the accompanying B meson. The CP-violation parameters are extracted from the asymmetries in the distributions of the proper-time intervals between the two B decays. The parameter sin 2ϕ1 is measured with the decay modes including the b→c tree and b→s penguin transitions, and sin 2ϕ2 is obtained from the decay mode B→π+π-. A brief discussion of the ϕ3 measurements with B→D(*)∓π± decays is also given.
Time-dependent CP violation in B decays at Belle