Further Evidence for an Increase of the Mean Mass of the Highest-Energy Cosmic-Rays with Energy

Abstract

Sokolsky and D_Avignon have recently reported an examination of a variety of measurements that relate to the question as to how the mass composition of the highest-energy cosmic-rays evolves with energy. They assert that cosmic rays arriving from the Northern Hemisphere have a different mass composition from those arriving from the Southern Hemisphere, implying a diversity of sources of high-energy cosmic-rays in the two hemispheres. Were this conclusion to be correct, it would have profound implications for theories of cosmic-ray origin and would influence planning of future projects. Their claim thus merits careful scrutiny. In this paper their analysis is examined in detail with the verdict being that evidence for a North/South difference is not proven, a conclusion supported by other data from the Northern and Southern Hemispheres. However, what is of major importance is that the study of Sokolsky and D_Avignon provides long-awaited confirmation of the claim that the mean mass of cosmic rays increases with energy above ~3 E eV made by the Pierre Auger Collaboration in 2014.

arXiv comment11 pages, 6 figures, 2 tables

References in corpus (5)

• Measurement of the cosmic-ray energy spectrum above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• Study of Ultra-High Energy Cosmic Ray Composition Using Telescope Array's Middle Drum Detector and Surface Array in Hybrid Mode
• Cosmogenic Neutrinos from Ultra-High Energy Nuclei
• The Impact of Heavy Nuclei on the Cosmogenic Neutrino Flux
• Mass composition of cosmic rays above 0.1 EeV by the Yakutsk array data

Cited by in corpus (4)

• Ultra-High-Energy Cosmic Rays: The Intersection of the Cosmic and Energy Frontiers
• Determination of the Cosmic-Ray Chemical Composition: Open Issues and Prospects
• Looking forward to forward physics at the CERN's LHC
• Model-independent Evidence for an Increase in the Mean Mass of Cosmic Rays above 3 EeV