Speaker
Description
Assuming an extreme scenario, in which the arriving cosmic rays are composed of only iron nuclei at energies above 10$^{19.6}$ eV, and preserving the elongation rate predicted by models of hadronic interactions, we derive the shift of the scale of the depth of shower maximum (Xmax) predicted by these models using the public data from the Pierre Auger Observatory. We then propose a new mass-composition model for the energy evolution of four primary species at the ultra-high energies by fitting the publicly-available Xmax distributions. We will discuss in detail the consequences of our new mass-composition model on the global consistency in arrival directions and tests of hadronic interactions, as well as the astrophysical conditions required for an iron-dominated scenario at the highest energies.
