ATLAS measurements of CP violation and rare decays processes with beauty mesons

The ATLAS experiment has performed measurements of B- meson rare decays proceeding via suppressed electroweak flavour changing neutral currents, and of mixing and $CP$ violation in the neutral Bs meson system. This talk will focus on the latest results from the ATLAS collaboration, such as rare processes $B^0_s \to \mu \mu$ and $B^0 \to \mu \mu$, and $CP$ violation in the $B_s^0 —> J/\psi \phi$ decays. In the latter, the Standard Model predicts the $CP$ violating mixing phase, $\phi_s$, to be very small and its SM value is very well constrained, while in many new physics models large $\phi_s$ values are expected. The latest measurements of $\phi_s$ and several other parameters describing the $B_s^0 \to J/\psi \phi$ decays will be reported.