Measurement of CP asymmetry in D 0 → K − K + and D 0 → π − π + decays

Time-integrated CP asymmetries in D 0 decays to the final states K − K + and π − π + are measured using proton-proton collisions corresponding to 3fb −1 of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D 0 mesons are produced in semileptonic b -hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in CP asymmetries between the two final states is measured to be Δ A CP = A CP K − K + − A CP π − π + = + 0.14 ± 0.16 stat ± 0.08 syst % .