# HiRes GZK Suppression Measurement (PRL, 2008)

**Type:** source
**Status:** Useful
**Confidence:** Medium
**Source Type:** peer-reviewed
**URL:** https://doi.org/10.1103/PhysRevLett.100.101101
**Publisher:** Physical Review Letters (American Physical Society)
**Updated:** 2026-08-11

## Summary

The High Resolution Fly's Eye (HiRes) collaboration's *Physical Review Letters* paper reporting the first observation of the Greisen–Zatsepin–Kuzmin (GZK) suppression in the ultra-high-energy cosmic-ray spectrum. HiRes operated in Utah's West Desert, which is why this measurement belongs to the state's scientific record.

## Useful Claims

- The paper is the peer-reviewed record for the HiRes collaboration's claimed first observation of the GZK suppression in the cosmic-ray spectrum.
- It is a collaboration paper, not a single-investigator result; authorship establishes the institutions involved.

## Reliability Notes

Primary tier: a paper in a peer-reviewed venue, cited by DOI, and retrievable by that DOI regardless of what happens to any publisher URL. That is why this page needs no archive snapshot while the university explainer it was split from does.

The claims above are deliberately thin, and are limited to what the citation itself establishes. Nothing here is quoted, because the article text has not been retrieved: APS is paywalled, so a `## Verbatim` section and any specific energy thresholds, spectral indices, or statistical significances must wait for a copy obtained legitimately — the arXiv preprint of this result is the obvious route, and adding it is a known gap rather than a finding.

Do not add figures to this page from memory or from secondary summaries. A number on a `peer-reviewed` page that is not in the paper is the worst failure mode in the corpus, because the tier makes it look checked.

## Related Pages

- [Fly's Eye and HiRes Ultra-High-Energy Cosmic Rays](flys-eye-hires-cosmic-rays.md)
- [Source: University of Utah Explainer on the Oh-My-God Particle](flys-eye-hires-cosmic-rays-source.md)