Searching for new symmetries in the Higgs sector at ATLAS

The discovery of the Higgs boson at the LHC experiments was a breakthrough, serving as a pivotal starting point for further exploration of the electroweak symmetry breaking mechanism. A key objective of the ATLAS experiment is to investigate the presence of additional Higgs bosons, which would indicate the existence of extended symmetries. In this talk, I present an overview of the recent searches conducted at the ATLAS experiment, specifically focusing on the searches for an additional spin-0 boson with a mass below 125 GeV, new scalar resonance in flavour-changing neutral-current top-quark decays, pseudo-scalar Higgs boson and doubly charged Higgs boson production. These Analysis conducted using LHC collision dataset at centre of mass energy of 13 TeV collected by the ATLAS experiment from 2015–2018.