2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48996We first discuss the theoretical and phenomenological significance of the sigma meson ($σ$) in QCD. It is indicated that if the collective modes with the mass 500-600 MeV exists in the $I=J=0$ channel, various empirical facts in hadron physics can be naturally accounted for, which otherwise would remain mysterious. We propose several experiments to produce and detect the $σ$ in nuclei using nuclear and electro-magnetic projectiles. The recent CHAOS data which show a spectral enhancement near the 2 $m_π$ threshold in the $σ$ channel from the reactions A$(π, 2π)$A' where A and A' denotes nuclei is interpreted as a possible evidence of a partial restoration of chiral symmetry in nuclei.Invited talk presented at the Workshop on Hadron Spectroscopy (whs99), Frascati- INFN, March 8 - 12, 1999. 8 pages with one figureHigh Energy Physics - PhenomenologyHigh Energy Physics - ExperimentNuclear ExperimentNuclear Theorytext