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

Abstract

Time-integrated CP asymmetries in D [superscript 0] decays to the final states K [superscript −] K [superscript +] and π [superscript −] π [superscript +] are measured using proton-proton collisions corresponding to 3 fb[superscript −1] of integrated luminosity collected at centre-of-mass energies of 7 TeV and 8 TeV. The D [superscript 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 ΔA[subscript CP] =A[subscript CP](K[superscript −]K[superscript +]) − A[subscript CP](π[superscript −]π[superscript +]) = (+0.14 ± 0.16 (stat) ± 0.08(syst))%. A measurement of A [subscript CP] (K [superscript −] K [superscript +]) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D decays. It is found to be A[superscript CP](K[superscript −]K[superscript +]) = (−0.06 ± 0.15(stat) ± 0.10(syst))%, where the correlation coefficient between ΔA [subscript CP] and A [subscript CP] (K [superscript −] K [superscript +]) is ρ = 0.28. By combining these results, the CP asymmetry in the D [superscript 0] → π [superscript −] π [superscript +] channel is A [subscript CP] (π [superscript −] π [superscript +]) = (−0.20 ± 0.19 (stat) ± 0.10 (syst))%.