Evidence of time-dependent CP violation in the decay B0 to D*+D*-

TL;DR

This paper reports the first evidence of time-dependent CP violation in B0 to D*+D*- decays, measuring CP-odd fractions and violation parameters using a large dataset from the Belle experiment.

Contribution

It provides the first measurement of CP violation parameters in B0 to D*+D*- decays, demonstrating time-dependent CP violation evidence.

Findings

CP-odd fraction Rperp=0.125±0.043(stat)±0.023(syst)

Evidence of CP violation with AD*+D*-=0.15±0.13(stat)±0.04(syst)

SD*+D*-=-0.96±0.25(stat)±0.13(syst)

Abstract

We report a measurement of the CP-odd fraction and the time-dependent CP violation in B0 to D*+D*- decays, using 657.10^6 BBbar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We measure a CP-odd fraction of Rperp=0.125+/-0.043(stat)+/-0.023(syst). From the distributions of the proper-time intervals between a B0to D*+D*- decay and the other B meson in the event, we obtain evidence of CP violation with measured parameters AD*+D*-=0.15+/-0.13(stat)+/-0.04(syst) and SD*+D*-=-0.96+/-0.25(stat)-0.16+0.13(syst).