First observation of CP violation and improved measurement of the branching fraction and polarization of B0 -> D*+ D*- decays

TL;DR

This paper reports the first observation of CP violation in B0 -> D*+ D*- decays, along with precise measurements of the branching fraction, polarization components, and CP violation parameters using a large data sample from the Belle experiment.

Contribution

It provides the first observation of CP violation in this decay mode and improves measurements of branching fraction and polarization with high statistical significance.

Findings

Branching fraction B = (7.82 +- 0.38 +- 0.63) x10^{-4}

CP-odd fraction R_ot = 0.138 +- 0.024 +- 0.006

CP violation parameter S_{D*+ D*-} = -0.79 +- 0.13 +- 0.03

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 million BB pairs, collected at the Y(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) x10^{-4}, a CP-odd fraction of R_\perp = 0.138 +- 0.024 +- 0.006 and, additionally, a fraction of the longitudinal component in the transversity base of R_0 = 0.624 +- 0.029 +- 0.011. The measured values of the parameters of the CP violation are S_{D*+ D*-} = -0.79 +- 0.13 +- 0.03 and A_{D*+ D*-} = 0.15 +- 0.08 +- 0.04.