Two Higgs doublet models and CP violating Higgs exchange in e+e−→tt̄Z

Appreciable CP asymmetries (∼10%) can arise in the reaction e+e−→tt̄Z already at tree-level in models with two Higgs doublets. For a neutral Higgs particle, h, with a mass in the range 50 GeV≲mh≲400 GeV, it may be possible to detect a 2–3 sigma CP-odd effect in e+e−→tt̄Z in ∼1–2 years of running of a future high energy e+e− collider with c.m. energies of ∼1–2 TeV and an integrated luminosity of 200–500 inverse fb.