2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46712Fermion compositeness and other new physics can be signalled by the presence of a strong four-fermion contact interaction. Here we present a study of $\ell\ell qq$ and $\ell\ell\ell'\ell'$ contact interactions using the reactions: $\ell^+ \ell^- \to \ell'^+\ell'^-,b\bar b, c\bar c$ at future $e^+e^-$ linear colliders with $\sqrt s=0.5-5$ TeV and $μ^+μ^-$ colliders with $\sqrt s=0.5,4$ TeV. We find that very large compositeness scales can be probed at these machines and that the use of polarized beams can unravel their underlying helicity structure.12 pg, to appear in the {\it Proceedings of the 1996 DPF/DPB Summer Study on New Directions for High Energy Physics - Snowmass96}, Snowmass, CO, 25 June - 12 July, 1996High Energy Physics - Phenomenologytext