Ultra High Energy Cosmic Rays: Gamma Ray Burst Messengers

Recent results from the Pierre Auger Observatory suggest that there might be a significant heavy component in high energy cosmic rays It is therefore interesting to explore the possibility to accelerate not only protons but also complex nuclei in relativistic jets We have investigated the acceleration of a mixed composition of cosmic rays in GRBs internal shocks taking into account all the relevant energy loss mechanisms during the acceleration process Three dimensional trajectories during the relativistic Fermi