Measurement of D0-D0bar Mixing and CP Violation at BaBar

TL;DR

This paper reports the first measurement of D0-D0bar mixing parameters and searches for CP violation using data from the BaBar experiment, providing evidence for mixing but no CP violation.

Contribution

The study presents the first measurement of the mixing parameter yCP and searches for CP violation in D0 decays using a large BaBar dataset, with improved precision and significance.

Findings

Measured yCP = 0.72% with statistical and systematic uncertainties.

Excluded the no-mixing hypothesis at 3.3 sigma significance.

Found no evidence of CP violation, with DeltaY consistent with zero.

Abstract

We report on a measurement of D0-D0bar mixing and a search for CP violation in the D0->K+K-, pi+pi- and K+-pi-+ channels. We use D0's coming from D*+ decays, so that the flavour of the D0 at production is tagged by the charge of the pion that is also emitted. We also use an independent set of D0's coming directly from the hadronization of the charm quark, but in this case the flavour of the charmed meson is not known. We analyze events collected by the BaBar experiment at the PEP-II asymmetric-energy e+e- collider, corresponding to an integrated luminosity of 468 fb-1. We measure the mixing parameter value to be yCP = [0.72 +- 0.18 (stat) +- 0.12 (syst)]%, and exclude the no-mixing hypothesis at 3.3sigma significance. We find no evidence of CP violation, observing DeltaY = [0.09 +- 0.26 (stat) +- 0.06 syst)]% which is consistent with zero.