Importance of gluon-gluon and quark-antiquark contributions to charmonium production in proton-proton and antiproton-proton collisions

The importance of the gluon-gluon and quark-antiquark contributions to the production of charmonium states in proton-proton and antiproton-proton collisions is determined within the parton model in a way which does not rely on any assumption on the dynamics (leading diagrams, color neutralisation mechanism,..). It is shown that the combined analysis of total and differential inclusive J/ψ production cross-sections for both systems allows such a determination. The primordial contributions are also extracted at one energy. The implications of the numerical values are also discussed. (orig.)