Rare and Semi-rare Decays of Beauty Mesons in ATLAS

The ATLAS experiment at the Large Hadron Collider (LHC) has performed measurements of the rare flavor-changing neutral-current processes $b \to s\,\mu^+\mu^-$ and $B^0_{(s)}\to \mu+\mu^-$ which are sensitive to New Physics effects. This contribution presents recent ATLAS results from the angular analysis of the $B^0\to K^{\star 0}\mu^+\mu^-$ decay with LHC Run 1 data, the $BR(B^0_{(s)}\to \mu+\mu^-)$ measurement with 2015 and 2016 data as well as projections for the $B^0\to K^{\star 0}\mu^+\mu^-$ and $BR(B^0_{(s)}\to \mu+\mu^-)$ measurements for the High-Luminosity LHC (HL-LHC) phase.