ATLAS measurements of CP Violation and Rare decays processes with Beauty mesons

The ATLAS experiment has performed accurate measurements of mixing and CP violation in the neutral B mesons, and also of rare neutral B-meson decays proceeding via electroweak FCNC-suppressed processes. This talk will focus on the latest results from ATLAS, such as rate measurements of B^0_s → mu mu and B^0 → mu mu decaysand CP violation in 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. Latest measurements of phi_s and several other parameters describing the B_s^0 —> J/psi phi decays will be reported.