Gluonia in QCD with massless quarks

Abstract

I 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 ${\eta }^{\prime }$ in the $U(1{)}_A$ sector.

Comments: talk given at the HEP 97, Jerusalem (1997)