Consequences of a Heavy-Metal Scenario of Ultra-High-Energy Cosmic Rays

Abstract

We assume an extreme scenario, in which the arriving cosmic rays are composed of only iron nuclei at energies above $10^{19.6}\text{eV}\simeq 40\text{EeV}$, while allowing a freedom in the scale of the depth of shower maximum ($X_{\max }$) and preserving the elongation rate and fluctuations of $X_{\max }$ predicted by models of hadronic interactions. We derive the shift of the $X_{\max }$ scale for QGSJet II-04 and Sibyll 2.3d 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 $X_{\max }$ distributions. We discuss the consequences of this Heavy-metal scenario on the energy spectrum of individual primary species, hadronic interaction studies, and the effect of the Galactic magnetic field on the arrival directions.

Proceedings of 7th International Symposium on Ultra High Energy Cosmic Rays (UHECR2024), 17-21 November 2024, Malargüe, Argentina. Published April 29, 2025

Cited by in corpus (1)

• A Heavy-Metal Scenario of Ultra-High-Energy Cosmic Rays