$W^{+}{W}^{-}H$ Production at Lepton Colliders: A New Hope for Heavy Neutral Leptons

We present the first study of the production of a Standard Model Higgs boson at a lepton collider in association with a pair of W bosons, $e^+{} e^-{} \to W^+{} W^-{} H$, in the inverse seesaw model. Taking into account all relevant experimental and theoretical constraints, we find sizable effects due to the additional heavy neutrinos up to -38% on the total cross-section at a center-of-mass energy of 3 TeV, and even up to -66% with suitable cuts. This motivates a detailed sensitivity analysis of the process $e^+{} e^-{} \to W^+{} W^-{} H$ as it could provide a new, very competitive experimental probe of low-scale neutrino mass models.