Search for rare decays of the observed Higgs boson and additional Higgs bosons with the ATLAS detector

The rare decays of the Standard Model (SM) Higgs boson and additional Higgs boson are searched for with the data recorded by the ATLAS experiment during the LHC pp collision run at 13 TeV corresponding to an integrated luminosity of $139{fb}^{-1}$. For the search for the dimuon decay of the SM Higgs boson, the observed (expected) significance is 2.0σ (1.7σ), and the signal strength is 1.2 ± 0.6. For the search for the Zγ decay of SM Higgs boson, the observed (expected) significance is 2.2σ (1.2σ), and the signal strength is ${2.0}_{-0.9}^{+1.0}$. For the search for new heavy resonance decaying into photon pairs, the mass range of the search has reached 3 TeV and no significant deviation from the SM is observed. These searches provide us a deeper understanding of the Higgs sector. (paper)