Probing the Higgs sector at the FCC-ee

This thesis examined three observables relevant to the Standard Model Higgs sector, which are the Higgs boson mass, its production cross section and the trilinear self-coupling, and estimated the performance of the measurement of these parameters at the FCC-ee. Compared to the previous analysis we introduced more Higgs boson production channels at $\sqrt{s}$ = 240, 365 GeV, used improved Monte Carlo samples (including initial and final state radiation) and a new orthogonal categorization of events. The Higgs boson mass was constrained to be within 5.6 MeV around the nominal value of 125 GeV at 68% CL using inclusive leptonic Higgsstrahlung channels at both energies. We used inclusive Higgsstrahlung (leptonic and hadronic) and exclusive vector boson fusion channels in a combined analysis to extract the sensitivity on the respective cross sections as well as on the trilinear self-coupling. The signal strength modifiers used to estimate the precision on the Higgsstrahlung and vector boson fusion production cross sections were measured with sub-percent and percent precision under the assumption that the decay of the Higgs boson follows the Standard Model expectation. In a similar manner, we extracted the Higgs boson trilinear self-coupling $\kappa_{\lambda}$ using one-loop corrections of the leading order Feynman diagrams of Higgsstrahlung and vector boson fusion. Assuming all parameters but $\kappa_{\lambda}$ are set to the Standard Model expectation, $\delta\kappa_{\lambda}$ can be constraint within [−0.29, 0.31] at 68% CL. This precision reach is compromised once multiple parameters of interest are left floating in the fit.