2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42916Using the newly modified method developed for symbolic evaluation of Feynman amplitudes we examine two processes $2\to 2$ (including a case of Majorana fermions) at a tree level. Constructing special polarization basis for spinor particles, we obtain compact expressions for helicity amplitudes. We present the regular way for simplification of evaluated symbolic expressions.8 pages, LaTeX, axodraw.styHigh Energy Physics - Phenomenologytext