Measurement of CKM element |Vcb| from W boson decays at the future Higgs factories

This study investigates the precision measurement of the CKM matrix element |Vcb| through semileptonic $WW$ events at future Higgs factories, $i.e.$, FCC-ee, ILC, C³, and CEPC. We use full detector simulation to generate the WW → ν cb signal events and various backgrounds at √s = 240 GeV with unpolarized beams. The relative statistical uncertainties are projected to be 0.91% for the muon channel and 1.2% for the electron channel, assuming a baseline integrated luminosity of 5 ab⁻¹. The sensitivities at other Higgs factory scenarios are also projected. Possible contributors to systematic uncertainties are discussed, with the most prominent one being the systematics of flavor-tagging and mistagging rates. Combining with $WW$ threshold runs, the relative systematic uncertainty can be further reduced.