Measurement of CP asymmetries in D^± → η^′π^± and D_s ^±→η^′π^± decays

A search for CP violation in D^±→η^′π^± and D_s ^±→η^′π^± decays is performed using proton–proton collision data, corresponding to an integrated luminosity of 3 fb⁻¹, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The measured CP-violating charge asymmetries are A_CP(D^±→η^′π^±)=(−0.61±0.72±0.53±0.12)% and A_CP(D_s ^±→η^′π^±)=(−0.82±0.36±0.22±0.27)%, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the A_CP(D^±→K_S ⁰π^±) and A_CP(D_s ^±→ϕπ^±) measurements used for calibration. The results represent the most precise measurements of these asymmetries to date.