Measurement of $\phi_s$

Precision measurements are needed in order to properly disentangle Standard Model (SM) contributions from possible New Physics (NP) effects, that could greatly affect CP observables. This document reviews the latest results from LHCb concerning CP violation using Run-1 data, for the decays $B^0_s \to J/\psi K^+K^-$, $B^0_s \to (K^+\pi^-)(K^-\pi^+)$ and $B^0_s \to \phi \phi$. The measurements presented for the first two channels are the world’s best results obtained up to date. All the discussed results constitute a considerable improvement with respect to previous ones. The corresponding uncertainties on the measurements are expected to the decrease with updates using Run-2 data.