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H-9 - The UHECR ankle and suppression are caused by GZK interactions of extragalactic protons with the CMB

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Properties11
type
hypothesis
id
H-9
state
active
question
What causes the UHECR spectral features, in particular the flux suppression above ~5e19 eV?
statement
The dip at ~4.6e18 eV (e+e- pair production) and the flux suppression at ~5.4e19 eV are caused by interactions of extragalactic protons with cosmic-microwave-background photons (the GZK process), implying a predominantly protonic composition at the highest energies - rather than the suppression being an instrumental artifact or an intrinsic cutoff of the sources.
cluster
HC-6 - Origin of the UHECR spectral structure
source
S-71 - Abu-Zayyad et al. 2013- Telescope Array surface-detector spectrum
quote
The spectrum obtained by our experiment demonstrates spectral features, a dip and a cutoff, consistent with the interaction of extra-galactic protons with the cosmic microwave background (GZK process).
merged_from
additional_sources
locator
  • S-71: §1 Introduction; §4; §5 Conclusions
  • S-60: opening ¶¶ (GZK prediction), interpretation and E1/2 discussion (p. 4), summary

Rival reading noted in the paper itself: Auger’s Xmax results may indicate a heavy composition at the highest energies, under which the suppression would be caused by spallation of heavy nuclei and the ankle would need a separate explanation.

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