Measurement of CP asymmetry in D-0 -> K- K+ decays

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D-0 -> K- K+ is performed using pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D*(+) -> D-0 pi(+) and D*(-) -> (D) over bar (0) pi(-) decays. The time-integrated CP asymmetry A(CP)(K- K+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D-0 -> K- pi(+), D+ -> K- pi(+) pi(+) and D+ -> (K) over bar (0) pi(+) decays used as calibration channels. It is found to be A(CP)(K- K+) = (0.14 +/- 0.15 ( stat) +/- 0.10 (syst))%. A combination of this result with previous LHCb measurements yields A(CP)(K- K+) = (0.04 +/- 0.12 ( stat) +/- 0.10 (syst))%, A(CP)( pi(-) pi(+)) = (0.07 +/- 0.14 ( stat) +/- 0.11 (syst))%. These are the most precise measurements from a single experiment. The result for ACP(K- K+) is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry.