Color transparency and final-state interactions in photonuclear charmonium production

The final-state interactions of quasielastically photoproduced charmonium have been computed in a quantum-mechanical QCD-inspired model for a range of photon energies and nuclear targets. In this model, charmonium in its rest frame interacts with an array of nucleon flux tubes via its color dipole moment as color electric fields flash on and off around it. The photoproduction amplitude is modeled as the narrowest superposition of open charmonium channels available at a given photon energy. A complete calculation of the final-state interactions has been performed; this involves retaining all the charmonium states present in the initial amplitude and produced upon interactions with the medium, and allowing them to scatter into each other upon further medium interactions. This work permits the computation of Aeff/A with and without transparency; the results support the utility of a study of the energy dependence of Aeff/A in elucidating transparency in the exclusive process considered. Moreover, a comparison of the underlying J/-nucleon cross section with that deduced from a Glauber analysis of the computed A dependence shows the Glauber analysis to be misleading.