Precision measurements of the Higgs boson decays in e⁺e⁻\!→ Z()H with H\!→ WW*\!→ νν at the FCC-ee

This note presents a feasibility study of the measurement of σ(e⁺e⁻→ ZH)(H→ WW^*) in the fully leptonic Z()H, H→ WW^*→νν (where = e,μ) final state at FCC-ee. The study uses Monte Carlo samples processed through a parameterized simulation of the IDEA detector concept. Separate analyses are performed for projected integrated luminosities of 10.8~ab⁻¹ at √s=240 GeV and 3.12~ab⁻¹ at √s=365 GeV. Events are reconstructed from four charged leptons (electrons and/or muons) and missing momentum, selected using kinematic requirements, and classified with boosted decision trees. A binned likelihood fit to the classifier output gives expected relative precisions of 3.09% and 7.33% at 240 and 365 GeV, respectively, and 2.90% for their combination.