Ultra High Energy Cosmic Ray Protons: Signatures and Observations

Abstract

The status of the Greisen-Zatsepin-Kuzmin (GZK) cutoff and pair-production dip in Ultra High Energy Cosmic Rays (UHECR) is discussed.They are the features in the spectrum of protons propagating through CMB radiation in extragalactic space, and discovery of these features implies that primary particles are mostly extragalactic protons. The spectra measured by AGASA, Yakutsk, HiRes and Auger detectors are in good agreement with the pair-production dip, and HiRes data have strong evidences for the GZK cutoff. The Auger spectrum,as presented at the 30th ICRC 2007, agrees with the GZK cutoff, too. The AGASA data agree well with the beginning of the GZK cutoff at E \leq 80 EeV, but show the excess of events at higher energies, the origin of which is not understood. The difference in the absolute fluxes measured by different detectors disappears after energy shift within the systematic errors of each experiment.

Plenary talk at NOW 2008 Wirkshop, 6 pages, 5 figures

References in corpus (4)

• First Observation of the Greisen-Zatsepin-Kuzmin Suppression
• Observation of the suppression of the flux of cosmic rays above 4x10^19eV
• A dip in the UHECR spectrum and the transition from galactic to extragalactic cosmic rays
• Ultra-high energy cosmic rays, cascade gamma-rays, and high-energy neutrinos from gamma-ray bursts

Cited by in corpus (6)

• Centaurus A: the one extragalactic source of cosmic rays with energies above the knee
• Cosmic rays in galactic and extragalactic magnetic fields
• Intergalactic Magnetic Field and Arrival Direction of Ultra-High-Energy Protons
• On ultra-high energy cosmic rays: origin in AGN jets and transport in expanding Universe
• Multiscale autocorrelation function: a new approach to anisotropy studies
• Anisotropy studies with multiscale autocorrelation function