Production of phi, psi, and charmed hadrons in strong interactions

It is shown that an SU(4) quark-gluon model is a specific realization of a scaling rule proposed by the authors for understanding hadronic production of heavy particles, including the recently discovered psi particles. The model leads to predominantly associated production of phi and psi (e.g., pairs). It is emphasized that tests of the charmonium picture for psi particles can be made independently by looking to see whether phi mesons are predominantly associatively produced