Measurement of CP asymmetries in $ {\overline{B}}^0\to {D}_s^{-}{D}^{+} $ and $ {\overline{B}}_s^0\to {D}_s^{-}{D}^{-} $ decays

Measurements of the combined CP asymmetries in ${\overline{B}}^0\to {D}_s^{-}{D}^{+}$ and ${\overline{B}}_s^0\to {D}_s^{-}{D}^{-}$ decays are made using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . The measurements are found to be ${\displaystyle \begin{array}{l}{A}_{CP}\left({\overline{B}}^0\to {D}_s^{-}{D}^{+}\right)=0.0009\pm 0.0053\pm 0.0040,\\ {}{A}_{CP}\left({\overline{B}}_s^0\to {D}_s^{-}{D}^{-}\right)=0.103\pm 0.053\pm 0.010,\end{array}}$ A CP B ¯ 0 → D s − D + = 0.0009 ± 0.0053 ± 0.0040 , A CP B ¯ s 0 → D s − D − = 0.103 ± 0.053 ± 0.010 , where the first and second uncertainties are statistical and systematic, respectively. This is the first measurement of this asymmetry in ${\overline{B}}_s^0$ decays, and the most precise measurement to date for ${\overline{B}}^0$ decays. Both measurements are found to be consistent with CP symmetry.