Testing CP-violation in a heavy Higgs sector at CLIC

We propose a method for probing 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 $Ht\overline{t}$ 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 $t\overline{t}$ 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 $t\overline{t}$ pairs. We analyze the distribution of the azimuthal angle between the leptons coming from top and antitop quarks, which allows one to disentangle the CP nature of such a heavy Higgs state. We also show its implications for the two-Higgs-doublet model (2HDM) with CP-violation.