Measurement of the direct $CP$-violating charge asymmetry in $D_s^{\pm }\to \varphi {\pi }^{\pm }$ decays

We present a measurement of the direct $CP$-violating charge asymmetry in $D_s^{\pm }\to \varphi {\pi }^{\pm }$ decays where the $\varphi$ meson decays to $K^{+}{K}^{-}$, using the full Run II data set with an integrated luminosity of 10.4 fb${}^{-1}$ of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. The normalised difference $A_{CP}$ in the yield of $D_s^{+}$ and $D_s^{-}$ mesons in these decays is measured by fitting the difference between their reconstructed invariant mass distributions. This results in an asymmetry of $A_{CP}=[-0.38\pm 0.27]$, which is the most precise measurement of this quantity to date. The result is consistent with the standard model prediction of zero $CP$ asymmetry in this decay. Updated to include changes made after referees comments. Corrected an affiliation in the author list.