Measurement of CP asymmetries in B̄⁰→ Dₛ⁻D⁺ and B̄ₛ⁰→ Dₛ⁻D⁻ decays

A bstract Measurements of the combined CP asymmetries in B̄⁰→ Dₛ⁻D⁺ B ¯ 0 → D s − D + and B̄ₛ⁰→ Dₛ⁻D⁻ B ¯ s 0 → 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 $$ { {array}{l}{A}CP({B̄}^0→ {D}_s⁻{D}⁺)=0.0009± 0.0053± 0.0040,\\ {}{A}CP({B̄}_s^0→ {D}_s⁻{D}⁻)=0.103± 0.053± 0.010,{array}} $$ 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 B̄ₛ⁰ B ¯ s 0 decays, and the most precise measurement to date for B̄⁰ B ¯ 0 decays. Both measurements are found to be consistent with CP symmetry.