2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/226494Non-zero width and Coulomb rescattering effects are analyzed for the pair production of smuons and selectrons near the thresholds in e+ e- and e- e- collisions, respectively. The excitation curves are predicted in a gauge-invariant form. Energy cuts are designed to reduce irreducible supersymmetric backgrounds.17 pages, 8 figures, few typos corrected, version to appear in EPJ CHigh Energy Physics - Phenomenologytext