Evidence for CP Violation in B0 -> D+D- Decays

TL;DR

This paper reports evidence of CP violation in B0 -> D+D- decays, measuring the branching fraction and CP parameters with a large data sample, revealing potential deviations from Standard Model predictions.

Contribution

First measurement of CP violation parameters in B0 -> D+D- decays using Belle data, indicating possible new physics beyond the Standard Model.

Findings

Evidence of CP violation at 4.1 sigma confidence level.

Measured branching fraction: (1.97 +- 0.20 +- 0.20) x 10^-4.

Parameter A suggests large direct CP violation, contradicting Standard Model expectations.

Abstract

We report measurements of the branching fraction and CP violation parameters in B0 -> D+D- decays. The results are based on a data sample that contains 535 x 10^6 BBbar pairs collected at the Upsilon(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e- collider. We obtain [1.97 +- 0.20 (stat) +- 0.20 (syst)] x 10^(-4) for the branching fraction of B0 -> D+D-. The measured values of the CP violation parameters are: S = -1.13 +- 0.37 +- 0.09, A = 0.91 +- 0.23 +- 0.06, where the first error is statistical and the second is systematic. We find evidence of CP violation in B0 -> D+D- at the 4.1 sigma confidence level. While the value of S is consistent with expectations from other measurements, the value of the parameter A favors large direct CP violation at the 3.2 sigma confidence level, in contradiction to Standard Model expectations.