First Observation of CP Violation in the Decays of B-s(0) Mesons

Using pp collision data, corresponding to an integrated luminosity of 1.0fb−1, collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in B0s→K−π+ decays, AC/!P(B0s→K−π+)=0.27±0.04(stat)±0.01(syst), with significance exceeding five standard deviations. This is the first observation of CP violation in the decays of B0s mesons. Furthermore, we provide an improved determination of direct CP violation in B0→K+π− decays, AC/!P(B0→K+π−)=−0.080±0.007(stat)±0.003(syst), which is the most precise measurement of this quantity to date.