Measurement of CP asymmetries in D+ (s) → ηπ+ and D+ (s) → η 0π + decays

Abstract

Searches for CP violation in the decays D + (s) → ηπ+ and D + (s) → η 0π + are performed using pp collision data corresponding to 6 fb−1 of integrated luminosity collected by the LHCb experiment. The calibration channels D + (s) → φπ+ are used to remove production and detection asymmetries. The resulting CP-violating asymmetries are A CP (D+ → ηπ+) = (0.34 ± 0.66 ± 0.16 ± 0.05)%, A CP (D+ s → ηπ+) = (0.32 ± 0.51 ± 0.12)%, A CP (D+ → η 0π +) = (0.49 ± 0.18 ± 0.06 ± 0.05)%, A CP (D+ s → η 0π +) = (0.01 ± 0.12 ± 0.08)%, where the first uncertainty is statistical, the second is systematic and the third, relevant for the D+ channels, is due to the uncertainty on ACP (D+ → φπ+). These measurements, currently the most precise for three of the four channels considered, are consistent with the absence of CP violation. A combination of these results with previous LHCb measurements is presented.