2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82667Medium effects as a function of the mass number $A$ are studied in the total photonuclear cross section from the $Δ$-resonance region up to the region where shadowing effects are known to exist. A consistent picture is obtained by simply assuming a density dependence of the different mechanisms of resonance broadening and shadowing. The $Δ$-mass shift is found to increase with $A$.7 pages, LaTeX, 2 figures available from the authorsNuclear Theorytext