First observation of CP violation and improved measurement of the branching fraction and polarization of B-0 -> D*(+) D*(-) decays

Abstract

We report the measurement of the branching fraction, the polarization, and the parameters of the time-dependent CP violation in B0→D*+D*− decays using a data sample of 772×106BB pairs, collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e− collider. We obtain a branching fraction of B=(7.82±0.38±0.63)×10−4, a CP-odd fraction of R⊥=0.138±0.024±0.006 and, additionally, a fraction of the longitudinal component in the transversity base of R0=0.624±0.029±0.011. The measured values of the parameters of the CP violation are SD*+D*−=−0.79±0.13±0.03 and AD*+D*−=0.15±0.08±0.04.