A search for time-integrated CP violation in D0 -> h- h+ decays

TL;DR

This paper reports a search for time-integrated CP violation in D0 meson decays to kaons and pions, finding a 3.5 sigma deviation from CP conservation using data from the LHCb experiment.

Contribution

First measurement of CP asymmetry difference in D0 decays to K+K- and pi+pi- with 0.6 fb-1 of LHCb data, indicating possible CP violation.

Findings

Measured Delta ACP = -0.82% with statistical and systematic uncertainties.

Observed a 3.5 sigma deviation from CP conservation.

Provides evidence for CP violation in charm decays.

Abstract

The preliminary results of a search for time-integrated CP violation in D0 -> h- h+ (h=K, pi) decays performed with 0.6 fb-1 of data collected by LHCb in 2011 are presented. The flavour of the charm meson is determined by the charge of the slow pion in the D*+ -> D0 pi+ and D*- -> D0bar pi- decay chains. The difference in CP asymmetry between D0 -> K- K+ and D0 -> pi- pi+, Delta ACP = ACP(K- K+) - ACP(pi- pi+), is measured to be Delta ACP = [ -0.82 +- 0.21 (stat.) +- 0.11 (syst.) ] %. This differs from the hypothesis of CP conservation by 3.5 sigma.