2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47455I briefly review the estimate of the gluonia masses, decay and mixings in QCD with massless quarks from QCD spectral sum rules and some low-energy theorems. The data in the $0^{++}$ channel can be explained with some maximal gluonium-quarkonium mixing schemes, which then suggest a large violation of the OZI rule, similar to the case of the $η'$ in the $U(1)_A$ sector.talk given at the HEP 97, Jerusalem (1997)High Energy Physics - PhenomenologyHigh Energy Physics - ExperimentHigh Energy Physics - LatticeNuclear Theorytext