Sophia { Simulations of Photohadronic Interactions in Astrophysics

We present a new Monte Carlo code for multiparticle production in collisions of nucleons with photons of an ambient photon eld. The nucleon-photon cross section is reproduced in terms of excitation/decay of baryon resonances, direct single pion production, diiractive scattering and non{diiractive multiparticle production. A complete simulation of the nal state is performed including all astrophysically relevant interaction processes up to p s ' 1000 GeV. We demonstrate that our model is capable of reproducing known accelerator data over a wide range in energy. Quantities frequently used in astrophysical applications like inelasticities and multiplicities are calculated and compared with the predictions of the widely used {approximation.