Possibility of Probing an Extra Higgs Boson at the Compact Linear Collider

We study the sensitivity of the Compact Linear Collider (CLIC) to an additional neutral Higgs boson $H$ through the vector boson fusion process $e^{+}{e}^{-}\to H\nu \bar{\nu }$, followed by the decay $H\to W^{+}{W}^{-}$, with both $W$ bosons decaying leptonically, resulting in a dilepton plus missing transverse energy final state. Within the framework of the Two Higgs Doublet Model, where both production and decay are governed by the Higgs mixing angle $\cos (\beta -\alpha )$, we perform a detector-level analysis and show that a high-energy CLIC can probe $H$ via this channel, allowing a direct measurement of the $HWW$ coupling.