We have examined the production of J/ψ mesons in high energy
proton-proton and proton-nucleus collisions at beam energies in the range from
158 GeV to 920 GeV, available from different fixed target experiments. In the
employed model J/ψ production in hadronic collisions is assumed to be a
factorisable two step process: (i) production of a ccˉ pair which can be
reliably described by perturbative QCD, and (ii) formation of J/ψ
resonance from the ccˉ pair, which can be conveniently parameterized
incorporating different existing physical mechanisms of color neutralization.
We show that, for lower collision energies, J/ψ production through
quark-anti-quark annihilation gives larger contribution at higher xF​, while
gluon-gluon fusion dominates the production at smaller xF​. For
proton-nucleus collisions the model takes into account both the initial state
modification of parton distributions in nuclei and the final state interaction
of the produced ccˉ pairs with the target nucleons. The model is found
to give reasonable description of data on J/ψ production in protonic and
proton-nucleus collisions, for different existing fixed target experiments. In
case of proton-nucleus collisions, our calculations show a non-negligible
dependence of the final state nuclear dissociation of J/ψ mesons on the
energy of the incident proton beam. The model has been applied to predict the
J/ψ production and suppression expected in proton-nucleus collisions at
energies relevant to FAIR, the upcoming accelerator facility at Darmstadt,
Germany. The amount of suppressions, for different mechanisms of J/ψ
hadronization has been found to be distinguishably different which might help
an experimental settlement of the much controversial issue of color
neutralization.Comment: 17 pages, 37 figures. To appear in Physical Review