2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42324A feasibility study of a 500-GeV linear collider is presented for mSUGRA models in co-annihilation region. We find an active mask is critical to suppress $e^+ e^- \to e^+ e^- τ^+ τ^-$ events to probe the models.4 pages, latex, 1 figure, talk at International Workshop on Linear Colliders - Workshop on Physics and Experiments with Future Electron-Positron Linear Colliders (LCWS2002), Jeju Island, Korea, August 26-30, 2002; Table 3 is updatedHigh Energy Physics - PhenomenologyHigh Energy Physics - Experimenttext