First Observation of CP Violation in B^0 →D(*)_(CP)h^0 Decays by a Combined Time-Dependent Analysis of BABAR and Belle Data

Abstract

We report a measurement of the time-dependent CP asymmetry of B^0 →D(*)_(CP)h^0 decays, where the light neutral hadron h^0 is a π^0, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K−, K^0_S π^0, or K^0_Sω. The measurement is performed combining the final data samples collected at the Υ(4S) resonance by the BABAR and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain (471±3)×10^6 BB pairs recorded by the BABAR detector and (772±11)×10^6 BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters –η_fS=+0.66±0.10(stat)±0.06(syst) and C=−0.02±0.07(stat)±0.03(syst). These results correspond to the first observation of CP violation in B^0 →D(*)_(CP)h^0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.

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