The GZK horizon and constraints on the cosmic ray source spectrum from observations in the GZK regime

Abstract

We discuss the GZK horizon of protons and present a method to constrain the injection spectrum of ultrahigh energy cosmic rays (UHECRs) from supposedly identified extragalactic sources. This method can be applied even when only one or two events per source are observed and is based on the analysis of the probability for a given source to populate different energy bins, depending on the actual CR injection spectral index. In particular, we show that for a typical source density of $4\times 10^{-5}Mp{c}^{-3}$, a data set of 100 events above $6\times 10^{19}$ eV allows one in 97% of all cases to distinguish a source spectrum $dN/dE\propto E^{-1.1}$ from one with $E^{-2.7}$ at 95% confidence level.

v2: 5 pages, 3 figures; shortened, title changed, matches version to be published

References in corpus (3)

• Search for Correlations between HiRes Stereo Events and Active Galactic Nuclei
• On the ultra-high energy cosmic ray horizon
• On the interpretation of the cosmic-ray anisotropy at ultra-high energies

Cited by in corpus (5)

• High energy radiation from Centaurus A
• Propagation of Ultra High Energy Cosmic Rays in Extragalactic Magnetic Fields: A view from cosmological simulations
• Cosmic Ray Origin: Lessons from Ultra-High-Energy Cosmic Rays and the Galactic/Extragalactic Transition
• The flux suppression at the highest energies
• Search for Individual Ultrahigh Energy Cosmic Ray Sources in the Future Data