2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/83053We show how the nuclear medium affects the masses of the $η$ and $η'$ mesons. The change should be easily detectable for dense matter and/or strong $η(η')N\bar N$ coupling. We also find that the $η-η'$ mixing angle is less in magnitude in the nuclear matter than in vacuum.LaTeX file + 5 figures, requires epsf.styNuclear Theorytext