Probing Higgs Sector CP Violation with Top Quarks at a Photon Linear Collider

We investigate for two-Higgs doublet models with intrinsic CP violation in the scalar potential CP-nonconserving effects in unpolarized $\gamma \gamma \rightarrow t \bar{t} $ for a range of neutral Higgs boson masses which includes resonant $\varphi$ production and the subsequent decay of $\varphi \rightarrow t \bar{t}$. The importance of taking into account, even in the resonant case, the interference with the nonresonant background is shown. Further, we propose and calculate three asymmetries which efficiently trace CP-violating effects in $\gamma \gamma \rightarrow t \bar{t} $ using semileptonic $t \bar{t}$ decays.