Soft and hard QCD dynamics in hadroproduction of charmonium

Abstract

Both hard and soft QCD dynamics are important in charmonium production, as presented here through a next-to-leading order QCD matrix element calculation combined with the color evaporation model. The observed xF and p⊥ distributions of J/ψ in hadroproduction at fixed target and p￣p collider energies are reproduced. Quite similar results can also be obtained in a more phenomenologicallyuseful Monte Carlo event generator where the perturbative production of c￣c pairs is instead obtained through leading order matrix elements and the parton shower approximation of the higher order processes. The soft dynamics mayalternativ elyb e described bythe soft color interaction model, originallyin traduced in connection with rapiditygaps. We also discuss the relative rates of different charmonium states and introduce an improved model for mapping the continuous c￣c mass spectrum on the physical charmonium resonances.