2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/181681In this paper we estimate the influence of the shadowing effect and initial state parton energy loss in the quarkonium production at HERA-B. We analyze the $x_F$ behavior of the effective exponent $α(x_F)$ and present a comparison with the preliminary HERA-B data for $J/Ψ$ production. Moreover, we estimate the magnitude of these effects in the $J/Ψ$ production at RHIC.9 pages, 4 figuresHigh Energy Physics - PhenomenologyNuclear Theorytext