Measurement of CP asymmetries in $D^{\pm} \to \eta^{\prime}\pi^{\pm}$ and $D^{\pm}_{s} \to \eta^{\prime}\pi^{\pm}$ decays

A search for CP violation in $D^{\pm} \to \eta^{\prime}\pi^{\pm}$ and $D^{\pm}_{s} \to \eta^{\prime}\pi^{\pm}$ decays 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 $\mathcal{A}_{CP}(D^{\pm} \to \eta^\prime \pi^{\pm}) = (−0.61 \pm 0.72 \pm 0.53 \pm 0.12)$% and $\mathcal{A}_{CP}(D^{\pm}_s \to \eta^\prime \pi^{\pm}) = (−0.82 \pm 0.36 \pm 0.22 \pm 0.27)$%, where the first uncertainties are statistical, the second systematic, and the third are the uncertainties on the $\mathcal{A}_{CP}(D^{\pm} \to K^{0}_{S}\pi^{\pm})$ and $\mathcal{A}_{CP}(D^{\pm}_{s} \to \phi\pi^{\pm})$ measurements used for calibration. The results represent the most precise measurements of these asymmetries to date