Testing CP-violation in a Heavy Higgs Sector at CLIC

We propose to probe CP-violation in the heavy (pseudo)scalar sector of an extended Higgs model, in which we make simultaneous use of the $HVV$ ($V=W^{\pm },Z$) and $Ht\bar{t}$ interactions of a heavy Higgs state $H$. The CP-even component of $H$ can be probed through the tree level $HVV$ interaction while the CP-odd component of $H$ can be probed if the final $t\bar{t}$ pair can be tested to form a ${}^1{S}_0$ state. We can then confirm CP-violation if both CP-even and CP-odd components of $H$ are discovered. This is possible at the Compact Linear Collider (CLIC) by exploiting $H$ production from Vector-Boson Fusion (VBF) and decay to $t\bar{t}$ pairs. We analyze the distribution of the azimuthal angle between the leptons coming from top and antitop quarks, that would allow one to disentangle the CP nature of such a heavy Higgs state. We also show its implications for the 2-Higgs-Doublet Model (2HDM) with CP-violation.