Flavour tagging techniques for CPV studies in the Bs system with ATLAS

The sensitivity to $B_s$ meson mixing phenomena can be significantly improved by distinguishing the initial meson flavour. We present the flavor tagging techniques, as used for instance in the ATLAS measurement of the angular amplitudes contributing to $B_s \rightarrow J/\psi(\mu^+\mu^-)\phi(K^+K^-)$ decays. The methods, their performance and calibration on self-tagged $B^+ \rightarrow J/\psi K^+$ data are shown.