On a possible photon origin of the most-energetic AGASA events

In this work the ultra high energy cosmic ray events recorded by the AGASA experiment are analyzed. With detailed simulations of the extensive air showers initiated by photons, the probabilities are determined of the photonic origin of the 6 AGASA events for which the muon densities were measured and the reconstructed energies exceeded 102 eV. On this basis a new, preliminary upper limit on the photon fraction in cosmic rays above 102 eV is derived and compared to the predictions of exemplary top-down cosmic-ray origin models