Sensitivity to New Phenomena via Higgs Couplings with the ATLAS Detector at a High-Luminosity 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 a High-Luminosity LHC has been estimated elsewhere using parametrized acceptances, efficiencies, and resolutions to approximate the expected detector performance. Expected limits on an additional electroweak singlet, an additional electroweak doublet (two-Higgs-doublet model), and 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 reach for new phenomena is significantly enhanced at a High-Luminosity LHC compared to the corresponding sensitivities at lower integrated luminosities.