Measurement of the mass of Higgs boson through HZ production 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 provide 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.