Z-Higgs production in Higgs Effective Field Theory at FCC-ee

In this thesis, we study Higgs production in association with a Z boson at a future e+e−collider. This process constitutes the dominant Higgs production mode and will play a central role at the Future Circular Collider (FCC-ee) in measuring the properties of the Higgs boson. Thanks to the extremely high luminosities expected at such a machine, precise determinations of Higgs couplings will become possible, providing sensitivity not only to tree-level effects but also to indirect contributions from loop-induced operators. A prominent example is the trilinear Higgs self-coupling, whose extraction relies on electroweak radiative corrections to ZH production. The combination of FCC-ee and HL-LHC measurements is expected to probe this coupling with an accuracy of about 15%, which degrades to roughly 30% when marginalising over all operators in the Standard Model Effective Field Theory (SMEFT) framework. The goal of this thesis is to assess how robust this projected sensitivity is with respect to the underlying effective-field-theory assumptions. To this end, we compute the one-loop corrections to ZH production within the Higgs Effective Field Theory (HEFT) and compare the resulting sensitivity to the trilinear Higgs self-coupling with that obtained in the SMEFT case.