Photoproduction of quarkonium from soft color exchanges

The authors discuss photoproduction of quarkonium states in the models of soft color interactions and the generalized area law for color string reinteractions as implemented in the Monte Carlo program AROMA. The physics of heavy quarks offers many probes for a better understanding of the interplay between perturbative and non-perturbative aspects of quantum chromogynamics. One such question is the production mechanisms for quarkonium states for which a complete understanding is not available presently. The color octet model can describe the large direct production of J/{psi}'s and {psi}'s at the Fermilab Tevatron, which is a factor of {approximately}30 above expectations from the color singlet model, but it does not seem to describe the polarization correctly. In addition, it does not seem to be consistent with data from HERA which agrees quite well with the color singlet model.