First Observation of CP Violation in B̅⁰ → D{CP}^{*}h⁰ Decays by a Combined Time-Dependent Analysis of BABAR and Belle Data

We report a measurement of the time-dependent CP asymmetry of B̅⁰ → D{CP}^*h⁰ decays, where the light neutral hadron h⁰ is a π⁰, η, or ω meson, and the neutral D meson is reconstructed in the CP eigenstates K⁺K⁻, K⁰{s}π⁰ or K{s}⁰ω. 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) x 10⁻⁶ BB̅ pairs recorded by the BABAR detector and (772 ± 11) x 10⁶ BB̅ pairs recorded by the Belle detector. We measure the CP asymmetry parameters -η{f}S = +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 B̅⁰ → D{CP}^*h⁰ decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.