Measurement of CP asymmetry in B s 0 → D s ∓ K ± decays

Abstract We report the measurements of the CP -violating parameters in B s 0 → D s ∓ K ± decays observed in pp collisions, using a data set corresponding to an integrated luminosity of 3.0 fb−1 recorded with the LHCb detector. We measure C f = 0.73 ± 0.14 ± 0.05, A f ΔΓ = 0.39 ± 0.28 ± 0.15, A f ¯ Δ Γ = 0.31 ± 0.28 ± 0.15 $$ {A}_{\overline{f}}^{\varDelta \varGamma }=0.31\pm 0.28\pm 0.15 $$ , S f = −0.52 ± 0.20 ± 0.07, S f ¯ = − 0.49 ± 0.20 ± 0.07 $$ {S}_{\overline{f}}=-0.49\pm 0.20\pm 0.07 $$ , where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the B s 0 mixing phase, −2β s , to obtain a measurement of the CKM angle γ from B s 0 → D s ∓ K ± decays, yielding γ = (128 − 22 + 17 )° modulo 180°, where the uncertainty contains both statistical and systematic contributions. This corresponds to 3.8 σ evidence for CP violation in the interference between decay and decay after mixing.