Sparticle Production in Electron-Photon Collisions

Abstract

We explore the potential of electron-photon colliders to measure fundamental supersymmetry parameters via the processes $eγ\to \tilde e \tildeχ^0$ (selectron-neutralino) and $eγ\to \tildeν\tildeχ^-$ (sneutrino-chargino). Given the $\tildeχ^0$ and $\tildeχ^-$ masses from $e^+e^-$ and hadron collider studies, cross section ratios $σ(γ_-)/σ(γ_+)$ for opposite photon helicities determine the $\tildeν_L$, $\tilde e_L$ and $\tilde e_R$ masses, independent of the sparticle branching fractions. The difference $m_{\tildeν_L}^2-m_{\tilde e_L}^2$ measures $M_W^2\cos2β$ in a model-independent way. The $\tilde e_L$ and $\tilde e_R$ masses test the universality of soft supersymmetry breaking scalar masses. The cross section normalizations provide information about the gaugino mixing parameters.