Testing the new physics scale in the B^{0} system @ ATLAS

Weak decays that are naturally suppressed in the Standard Model, such as processes with flavour-changing neutral-currents, are perfect for indirect searches of new physics. These decays allow us to investigate higher energy ranges with respect to direct searches thus representing a fundamental complementary tool. Results on the ATLAS analysis of the $B_{s} \rightarrow \mu^{+}\mu^{-}$ - rare decay will be presented together with prospects on future updates. The ATLAS study of $B_{d} \rightarrow K^{\ast} \mu^{+}\mu^{-}$ is also reported where the parameters $A_{FB}$ and $F_{L}$ are extracted from the angular distribution of the final state. Potential new physics is also investigated studying the $B_{s}^{0} \rightarrow J/\psi \phi$ decay to measure CP-violating phase $\phi_{s}$ and the latest results obtained by ATLAS are presented.