Implications of the cosmic ray spectrum for the mass composition at the highest energies

By D. Allard, N. Busca, G. Decerprit, Angela V. Olinto, É. Parizot. 2008

133 citations recorded by the source corpus.

The significant attenuation of the cosmic ray flux above ∼5 × 1019 eV suggests that the observed high energy spectrum is shaped by the so-called GZK effect (GZK: Greisen–Zatsepin–Kuzmin). This interaction of ultra-high energy cosmic rays (UHECRs) with the ambient radiation fields also affects their composition. We review the effect of photodissociation interactions on different nuclear species and analyze the phenomenology of secondary-proton production as a function of energy. We show that, by itself, the UHECR spectrum does not constrain the composition of cosmic rays at their extragalactic sources. While the propagated composition (i.e., as observed at Earth) cannot contain significant amounts of intermediate mass nuclei (say between He and Si), whatever the source composition, and while it is vastly proton dominated when protons are able to reach energies above 1020 eV at the source, we show that the propagated composition can be dominated by Fe and sub-Fe nuclei at the highest energies, either if the sources are very strongly enriched in Fe nuclei (a rather improbable situation), or if the accelerated protons have a maximum energy of a few 1019 eV at the sources. We also show that in the latter cases, the expected flux above 3 × 1020 eV is very much reduced as compared to the case when protons dominate in this energy range, both at the sources and at Earth.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/89fb6b78fd19c14b961b73b8ad9da7016db4073b

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Citations in the corpus

Cosmogenic neutrinos: parameter space and detectabilty from PeV to ZeV (2010, background): “…(i) a pure proton composition in the dip model case, (ii) a proton dominated mixed composition based on Galactic cosmic ray abundances as in Allard et al. (2006), (iii) a pure iron composition and (iv) a mixed composition that was proposed by Allard et al. (2008), that contains 30% of iron.”
Depth of Ultra High Energy Cosmic Ray Induced Air Shower Maxima Measured by the Telescope Array Black Rock and Long Ridge FADC Fluorescence Detectors and Surface Array in Hybrid Mode (2018, background): “…very few ultra high energy cosmogenic neutrinos), no anisotropy of nearby sources due to strong deflection in magnetic fields, and no cutoff in the spectrum due to the GZK mechanism since the maximum energy of astrophysical accelerators is too low (Allard et al. 2008; Aloisio et al. 2012).”
The Astrophysics of Ultrahigh-Energy Cosmic Rays (2011, background): “After pioneering work by Puget et al. (1976), energy losses for nuclei have been examined by several groups (Stecker & Salamon 1999; Epele & Roulet 1998a,b; Bertone et al. 2002; Khan et al. 2005; Allard et al. 2005, 2008; Hooper et al. 2005, 2008; Aloisio et al. 2008).”
The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) observatory (2020, background): “The same spectral feature may be produced by the maximum energy of the sources in models that also predict a change to heavier composition at the highest energies [42].”