The Mass of Cosmic Rays of Ultra High Energy

TL;DR

This paper reviews analyses indicating that ultra-high-energy cosmic rays are not primarily protons, suggesting a need to re-evaluate energy spectrum measurements for better consistency across observatories.

Contribution

It provides a comprehensive review of cosmic ray composition analyses and discusses implications for energy spectrum measurements using modern interaction models.

Findings

Cosmic rays at highest energies are not proton-dominated.

Re-evaluation of energy spectrum may improve agreement between observatories.

Use of modern hadronic interaction models is crucial for accurate interpretation.

Abstract

A review of several analyses is presented that forces the conclusion that the mass composition of the highest-energy cosmic rays is not proton-dominated. This deduction, combined with the use of a modern hadronic interaction model, should lead to a re-evaluation of the energy spectrum reported by the Telescope Collaboration that may well bring that measurement, and the corresponding one from the Pierre Auger Observatory, into better agreement.