Photoproduction cross-sections at HERA energies

We show that photoproduction cross sections recently measured by ZEUS and H-1 at HERA energies 1 are in agreement with our earlier prediction based on highenergy hadronic structure of the photon in the QCD minijet-type model 2 .W e present results of an improved calculation of the photoproduction cross section, in which the soft part, motivated by the Regge theory, is taken to be energy-dependent and the semi-hard hadronic part is carefully eikonalized to take into account for the multiple scatterings and to include the appropriate probability that photon would act hadronicaly 3 . We also show that the extrapolation of our cross section to ultrahigh energies, of relevance to the cosmic ray physics, gives signicant contribution to the \conventional" value, but cannot account for the anomalous muon content observed in the cosmic ray air-showers associated with astrophysical point sources 4 .