Indications of Proton-Dominated Cosmic-Ray Composition above 1.6 EeV

2009/10/31 by R. U. Abbasi, T. Abu-Zayyad, T. Abu‐Zayyad +77 · 10 citations
Physics and Astronomy · #Air shower #Astrophysics #Astrophysics and Cosmic Phenomena #Composition (language) #Cosmic ray #Dark Matter and Cosmic Phenomena #Hadron #Neutrino Physics Research #Nuclear physics #Observatory #Physics #Proton #Ultra-high-energy cosmic ray #X-ray #astro-ph.HE

paper · pdf · doi:10.1103/physrevlett.104.161101

published as Phys.Rev.Lett.104:161101,2010 · 11 pages, 4 figures, accepted for publication in Physical Review Letters

arxiv created 2010/04/03 · openalex publication_date 2010/04/20 · arxiv updated 2010/04/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X_max), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d⟨X_max⟩/d[log(E)] of 47.9\ifmmode±\else\textpm\fi6.0(stat)\ifmmode±\else\textpm\fi3.2(syst) g/cm²/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4\ifmmode×\else\texttimes\fi10¹⁸ eV.

Citations

• Observation of the Suppression of the Flux of Cosmic Rays above4×1019 eV
• A Study of the Composition of Ultra–High‐Energy Cosmic Rays Using the High‐Resolution Fly’s Eye
• Comparison of air fluorescence and ionization measurements of EM shower depth profiles: Test of a UHECR detector technique

Cited by

• Cosmological magnetic fields: their generation, evolution and observation
• Anisotropies of ultrahigh energy cosmic rays diffusing from extragalactic sources
• Update on tests of the Cen A neutron-emission model of highest energy cosmic rays
• Constraining sources of ultra high energy cosmic rays using high energy observations with the Fermi satellite
• The non-linearity between and induced by the acceptance of fluorescence telescopes
• A template method for measuring the iron spectrum in cosmic rays with Cherenkov telescopes
• Calculations of electric fields for radio detection of ultrahigh energy particles
• Neutrino background flux from sources of ultrahigh-energy cosmic-ray nuclei
• The Astrophysics of Ultrahigh-Energy Cosmic Rays
• Hadronic Interactions of Energetic Charged Particles in Protogalactic Outflow Environments and Implications for the Early Evolution of Galaxies

Related

• Propagation and Chemical Composition of Ultra High Energy Cosmic Rays
• Ultra-High Energy Cosmic Rays: Results and Prospects
• Precise measurements of the cosmic ray proton energy spectrum in the "knee'' region
• Experimental/Observational Summary - Very High Energy Cosmic Rays and their Interactions
• What do we know about cosmic rays with energies above 5 EeV?