First Observation of CP Violation in the Decays of Bs0 Mesons

Using pp collision data corresponding to an integrated luminosity of 1.0fb^-1 and collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in B_s⁰→K^-π⁺ decays, A_CP(B_s⁰→K^-π⁺)=0.27±0.04(stat)±0.01(syst), with significance exceeding 5 standard deviations. This is the first observation of CP violation in the decays of B_s⁰ mesons. Furthermore, we provide an improved determination of direct CP violation in B⁰→K⁺π^- decays, A_CP(B⁰→K⁺π^-)=-0.080±0.007(stat)±0.003(syst), which is the most precise measurement of this quantity to date.