Prospects for New Physics in Higgs Couplings Studies with the ATLAS Detector at the HL-LHC

The ATLAS experiment at the LHC determines the couplings of the Higgs boson to other particles using the combination of measurements from multiple production and decay channels. The expected precision with which these couplings can be measured at the High-Luminosity LHC has been estimated elsewhere using parametrized acceptances, efficiencies, and resolutions to approximate the expected detector performance with the upgraded detector. Expected constraints on a non-standard mass scaling of the couplings, as well as models with an additional electroweak singlet, an additional electroweak doublet (two-Higgs-doublet model), a composite Higgs boson, a simplified Supersymmetric Standard Model (MSSM), and a Higgs portal to dark matter, are derived here using the estimated precision on the coupling measurements with 300 and 3000 $\textrm{fb}^{-1}$ of $pp$ collision data at $\sqrt{s}=14$ TeV. The sensitivity to new phenomena is significantly enhanced at the High-Luminosity LHC compared to the corresponding sensitivities at lower integrated luminosities.