New physics searches with b-hadrons at the ATLAS experiment

Flavour changing neutral currents and precision measurements of CPviolation are investigated by the ATLAS experiment as probes to new physics beyond the standard model. This talk presents the most recent results on the search for the rare decay $B^0_s\rightarrow \mu^+\mu^-$, as well asthe latest update on the study of the various angular amplitudes contributing to flavour tagged$B^0_s\rightarrow J/\psi(\mu^+\mu^-)\phi(K^+K^-)$ decays. The latter analysis measures the CP-violating phase $\phi_s$, as well as the average $B_s$ meson lifetime $\Gamma_s$ and the decay width difference $\Delta\Gamma_s$