CHARM PHOTOPRODUCTION IN PERTURBATIVE QCD AND IN THE QUARK-GLUON STRING MODEL

The cross section for charm photoproduction at high energies is calcul ated in perturbative QCD and in the quark-gluon string model (QGSM). I n the case of QCD, the role of absorptive corrections to parton struct ure functions is considered. It is shown that such corrections can sig nificantly reduce the cross section for charm photoproduction at high energies and, especially, diminish the relative contribution of proces ses that are determined by the parton structure of photons. In the cas e of the QGSM, a significant contribution of the ''intrinsic charm'' i n the photon is required in order to attain agreement with experimenta l data on the total cross section for charm photoproduction and on the shape of the Do-meson spectrum. The relation between the contribution s from various processes in perturbative QCD and in the QGSM is discus sed. Predictions at HERA energies are made.