Measurement of CP asymmetry in $B_s^0\to D_s^{\mp }{K}^{\pm }$ decays

We report on measurements of the time-dependent CP violating observables in $B_s^0\to D_s^{\mp }{K}^{\pm }$ decays using a dataset corresponding to 1.0 fb${}^{-1}$ of pp collisions recorded with the LHCb detector. We find the CP violating observables $C_f=0.53\pm 0.25\pm 0.04$, $A_f^{\mathrm{\Delta }\mathrm{\Gamma }}=0.37\pm 0.42\pm 0.20$, $A_{\bar{f}}^{\mathrm{\Delta }\mathrm{\Gamma }}=0.20\pm 0.41\pm 0.20$, $S_f=-1.09\pm 0.33\pm 0.08$, $S_{\bar{f}}=-0.36\pm 0.34\pm 0.08$, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the $B_s^0$ mixing phase $-2{\beta }_s$ leads to the first extraction of the CKM angle $\gamma$ from $B_s^0\to D_s^{\mp }{K}^{\pm }$ decays, finding $\gamma$ = (115${}_{-43}^{+28}$)${}^{\circ }$ modulo 180${}^{\circ }$ at 68% CL, where the error contains both statistical and systematic uncertainties.