First Observation of CP Violation in ¯B0→D(*)CPh0 Decays by a Combined Time-Dependent Analysis of BABAR and Belle Data

Abstract

We report a measurement of the time-dependent C P asymmetry of ¯ B 0 → D ( * ) C P 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 C P eigenstates K + K − , K 0 S π 0 , or K 0 S ω . The measurement is performed combining the final data samples collected at the Υ ( 4 S ) 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 B ¯ B pairs recorded by the BABAR detector and ( 772 ± 11 ) × 10 6 B ¯ B pairs recorded by the Belle detector. We measure the C P 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 C P violation in ¯ B 0 → D ( * ) C P h 0 decays. The hypothesis of no mixing-induced C P violation is excluded in these decays at the level of 5.4 standard deviations.