Exploring Extended Higgs Dynamics via Higgsstrahlung at FCC-ee

Abstract

The Future Circular Electron-Positron Collider (FCC-ee) will probe aspects of the Higgs boson and the electroweak scale with unprecedented precision via associated Higgs production with a $Z$ boson. We focus on the Two-Higgs-Doublet Model (2HDM) to frame the FCC-ee's precision constraints within a small, concrete parameter space at next-to-leading order. We demonstrate that the projected precision of the FCC-ee's 240 GeV run will enable a precise analysis of Beyond-the-Standard-Model (BSM)-relevant Higgs-sector interactions near the alignment limit. As the key aspects of the 2HDM that drive deviations of the cross section from its Standard Model expectation (presence of new scalar states, Higgs mixing, and non-trivial inter-Higgs couplings) are also typically present in extensions more complex than the 2HDM, this demonstrates the FCC-ee's indirect potential for unveiling BSM physics around the electroweak scale.