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Regular version of the site

Article

Measurement of CP asymmetry in D0→ K− K+ decays

Hushchyn M., Ustyuzhanin A., Derkach D., Ratnikov F., Баранов А. С., Kazeev N., Borisyak M. A.

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D0KK+ is performed using pp collision data, corresponding to an integrated luminosity of 3fb1, 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+D0π+ and DD0π decays. The time-integrated CP asymmetry ACP(KK+) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D0Kπ+D+Kπ+π+ and D+K0π+ decays used as calibration channels. It is found to be

ACP(KK+)=(0.14±0.15(stat)±0.10(syst))%.

A combination of this result with previous LHCb measurements yields

ACP(KK+)=(0.04±0.12(stat)±0.10(syst))%,ACP(ππ+)=(0.07±0.14(stat)±0.11(syst))%.

These are the most precise measurements from a single experiment. The result for ACP(KK+) 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.