Tau Polarization as a Probe of Cp of a Light Higgs Boson

We study the polarization of τ leptons produced at a γγ collider in the reaction γγ → ττ as a possible probe of the Higgs (φ) contribution to this process and consequently of the Higgs CP property. We construct polarization asymmetries which can probe the γγφ and φττ couplings for both the CP-conserving and the CP-violating cases. We demonstrate the use of these asymmetries by analysing the CP-violating MSSM Higgs sector as an example. We show, numerically, that our asymmetries are sensitive to the CP property of a light Higgs boson over a wide range of MSSM parameters still allowed by OPAL searches.