Measurement of the CP-violating phase $\phi_s$ in $B_s^0 \to J/\psi \phi$ at ATLAS

The ATLAS experiment has performed measurement of mixing and CP violation in the neutral Bs meson system. This talk will focus on the latest results from the ATLAS collaboration, a CP violation in the $B_s^0 \to J/\psi \phi$ decay. The Standard Model predicts the CP violating mixing phase, $\phi_s$, to be very small and its SM value is very well constrained, while any measured deviations from SM value can indicate New Physics not described by SM. This contribution presents the $B_s^0 \to J/\psi \phi$ oscillation parameters obtained by decay-time-dependent angular analysis using $80.5 \; \mathrm{fb^{-1}}$ collected by the ATLAS detector in $pp$ collisions at the energy $13 \;\mathrm{TeV}$.