Probing HZZ Interactions through Single Production of Higgs Boson at FCC-ee

Abstract: The associated production of a Higgs boson with a Z boson in the collisions of electron and positron beams at Future Circular Collider (FCC-ee) have been studied. Here, the Z boson decays into dileptons, while the Higgs boson decays to all possible channels, mostly to the b\bar{b}. The collisions provides a clean and powerful channel to probe the (HZZ) coupling at future lepton colliders. Following the event generation, the analysis is performed using the recoil mass method, which allows model-independent reconstruction of the Higgs boson depending on the kinematics of the final-state leptons. This method enables precise identification of the Higgs signal peak independent of its decay mode and significantly reduces systematic uncertainties. The recoil mass distributions from the signal process (e^+e^- \to HZ, Z \to l^+l^-) and the main backgrounds (ZZ, WW, t\bar{t} and other standard model processes) have been analyzed using a dedicated analysis code. Monte Carlo simulations corresponding to an integrated luminosity of 5 ab^{-1} have been used for the analysis, assuming the high performance of the IDEA detector concept. The results are presented for center-of-mass energies of \sqrt{s} = 240 GeV and \sqrt{s} = 365 GeV to compare the sensitivities and highlight the potential of future e^+e^- colliders in probing the HZZ interaction with high precision.