The effects of Higgs boson couplings through HZZ production at future lepton colliders

Introduction We focus on the sensitivity of the anomalous Higgs-gauge boson couplings at H γ Z and H Z Z vertices through the process ℓ − ℓ + → H Z Z at CLIC and Muon Collider. Methods Signal and relevant backgrounds events are generated in MadGraph within Standard Model Effective Field Theory (SMEFT) framework. These events are passed through Pythia for parton showering, and realistic detector effects are simulated by Delphes. The limits at 95% C.L. on the coefficients cHB and cHW are obtained at two b-tagging working points; loose and medium containing the Delphes card from CLIC and Muon Collider, corresponding to b-tagging efficiencies of 90% and 70%, respectively. Results We report that our best 95% C.L. limits on cHB and cHW coefficients are [−0.00138;0.00090] and [−0.00162;0.00026], respectively, at 3 TeV CLIC with an integrated luminosity of 5 ab–1, and [−0.00024;0.00023] and [−0.00020;0.00009], respectively, at 10 TeV Muon Collider with an integrated luminosity of 10 ab–1. Discussion These limits are compared with the present experimental and various phenomenological limits.