Measurement of branching fraction and time-dependent CP asymmetry parameters in B^0 → D^*+D^*-K^{0}_{S}decays

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We present a measurement of the branching fraction and time-dependent CP violation parameters for B^0 → D^*+D^*-K^{0}_{S} decays. These results are obtained from a 414 fb^{-1} data sample that contains 449×10^6 B\bar{B} pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We obtain the branching fraction, B(B^0→D^*+D*^-K^{O}_{S})= [3.4±0.4(stat)±0.7(syst)]×10^-3, which is in agreement with the current world average. We also obtain an upper limit on the product branching fraction for a possible two-body decay, B(B^0 → D_s1^+(2536)D^*-)B(D_s1^+(2536)→ D^*+K^{O}_{S})<7.1×10^{-4} (90% CL). In the traditional 2-parameter time-dependent CP analysis, we measure the CP violation parameters, A_CP=-0.01^{+0.28}_{-0.28}(stat)±0.09(syst), Dsin2φ_1=0.06^{+0.45}_{-0.44}(stat)±0.06(syst). No evidence for either mixing-induced or direct CP violation is found. In a 3-parameter fit sensitive to cos2φ_1 performed in the half-Dalitz spaces, s^≤ s^+ and s^->s^+, where s^±[equivalent]m2(D^*±K^{0}_{S}), we extract the CP violation parameters, J_c/J_0=0.60^{+0.25}_{-0.28}(stat)±0.08(syst), 2J_s1/J_0sin2φ_1=-0.17^{+0.42}_{-0.42}(stat)±0.09(syst), 2J_s2/J_0cos2φ_1=-0.23^{+0.43}_{-0.41}(stat)±0.13(syst). A large value of J_c/J_0 would indicate a significant resonant contribution from a broad unknown D_s^**+ state. Although the sign of the factor, 2J_s2/J_0, can be deduced from theory, no conclusion can be drawn regarding the sign of cos2φ_1 given the errors.

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