Sparticle Production in Electron - Photon Collisions

We explore the potential of electron-photon colliders to measure fundamental supersymmetry parameters via the processes eγ → ˜ e ˜ χ 0 (selectron-neutralino) and eγ → ˜ ν ˜ χ − (sneutrino-chargino). Given the˜χ 0 and˜χ − masses from e + e − and hadron collider studies, cross section ratios σ(γ −)/σ(γ +) for opposite photon helicities determine the˜ν L , ˜ e L and˜e R masses, independent of the sparticle branching fractions. The difference m 2 ˜ ν L − m 2 ˜ e L measures M 2 W cos 2β in a model-independent way. The˜e L and˜e R masses test the universality of soft supersymmetry breaking scalar masses. The cross section normalizations provide information about the gaugino mixing parameters.