Probing CP-violating Higgs contributions in γγ → ff-bar

We discuss the use of fermion polarization for studying neutral Higgs bosons at a photon collider. To this aim we construct polarization asymmetries which can isolate the contribution of a Higgs boson φ in γγ→ ff-bar, f = Τ/t, from that of the QED continuum. This can help in getting information on the γγφ coupling in case φ is a CP eigenstate. We also construct CP-violating asymmetries which can probe CP mixing in case φ has indeterminate CP. Furthermore, we take the MSSM with CP violation as an example to demonstrate the potential of these asymmetries in a numerical analysis. We find that these asymmetries are sensitive to the presence of a Higgs boson as well as its CP properties over a wide range of MSSM parameters. (author)