Late Arriving Particles in Cosmic Ray Air Showers and AGASA's Determination of UHECR Energies

We give the first detailed study of the arrival time distribution of nucleons in UHECR air showers. We analyze in detail the influence of late arriving particles on the energy determination of the AGASA experiment, as well as how the arrival time distribution changes with distance from shower core. Our calculations are consistent with experimental observations of the AGASA group. Crucial to obtaining agreement, is the correct implementation of the energy loss for low-energy protons. We confirm AGASA's estimation of the error in their energy determination associated with late-arriving particles, assuming primary protons.