Multiple Hard Interactions in HERWIG

At HERA energies photoproduction of jets is sensitive to very high parton densities and so the probability of more than one hard partonic scattering occurring in a single photon-proton collision may be signiicant. This eeect has been simulated using an eikonal prescription for the generation of the hard processes and the HERWIG parton showering and hadronization models. The rst results on simulated jet cross sections indicate that the eeect could be important when interpreting measurements of jet cross sections at HERA, and that the presence of a signiicant amount of multiple hard interactions could be directly connrmed by experiment.