Measurement of CP asymmetry in B_s⁰ → D_s^∓ K ^± decays

We report the measurements of the CP -violating parameters in B_s⁰ → 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, Af=0.31±0.28±0.15, S_f = −0.52 ± 0.20 ± 0.07, S_f¯= − 0.49 ± 0.20 ± 0.07 , where the uncertainties are statistical and systematic, respectively. These parameters are used together with the world-average value of the B_s⁰ mixing phase, −2β_s, to obtain a measurement of the CKM angle γ from B_s⁰ → 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.