Name : Angela V. Olinto Institute : University of Chicago E-mail : olinto@oddjob.uchicago.edu TITLE : Origin of Super GZK particles ABSTRACT : Contrary to expectations, several cosmic ray events with energies above $10^{20}$ eV have been observed. The flux of such events is well above the predicted Greisen-Zatsepin-Kuzmin cutoff due to the pion production of extragalactic cosmic ray protons off the cosmic microwave background. In addition to the relatively high flux of events, the isotropic distribution of arrival directions and an indication of hadronic primaries strongly challenge all models proposed to resolve this puzzle. We discuss how the GZK cutoff is modified by the local distribution of galaxies and how astrophysical proton sources with soft injection spectra are ruled out by AGASA data. Sources with hard injection spectrum are barely allowed by these observations. We present an overview of the theoretical proposals along with their most general signatures to be tested by future experiments.