Sensitivity to invisible scalar decays at CLIC

We studied the possibility of measuring invisible Higgs boson decays at CLIC running 380 GeV and 1.5 TeV. The analysis is based on WHIZARD event generation fast simulation detector response with DELPHES. considered $e^+e^-$ background processes but also relevant $\gamma\gamma$ $\gamma e^\pm$ interactions. approach consisting a two step was used to optimize separation between signal processes. First, set preselection cuts applied; then, multivariate methods were employed optimise significance observations. estimated expected limits 125 boson, as well cross section for production an additional neutral Higgs-like scalar, assuming its decays, function mass. Extracted model-independent branching ratio then interpreted in framework vector-fermion dark matter model mixing angle SM-like Higss new scalar "dark sector".