Constraints on the spread of nuclear masses in ultra-high-energy cosmic rays based on the Phase I hybrid data from the Pierre Auger Observatory

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Main Author: Yushkov, Alexey
Format: Preprint
Published: 2025
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author Yushkov, Alexey
author_facet Yushkov, Alexey
contents We present an analysis of the correlation between the depth of the maximum of air-shower profiles and the signal in water-Cherenkov stations in events registered simultaneously by the fluorescence and surface detectors of the Pierre Auger Observatory. The analysis enables us to place constraints on the spread of nuclear masses in ultra-high-energy cosmic rays with a minor impact from the experimental systematic uncertainties and uncertainties in air-shower simulations. Due to this unique feature, the correlation analysis has previously allowed us to exclude all pure and proton-helium compositions near the ankle in the cosmic-ray energy spectrum at 5$σ$ confidence level. The same property makes the correlation analysis an effective tool for testing the consistency of predictions of the post-LHC hadronic interaction models, including their latest versions such as EPOS LHC-R, QGSJet-III-01, Sibyll${}^\bigstar$ and Sibyll 2.3e. In this work, the correlation analysis using the Phase I hybrid data from the Pierre Auger Observatory is presented. The analysis uses the newest generation of hadronic interaction models and covers an extended energy range around the ankle in the cosmic-ray spectrum.
format Preprint
id arxiv_https___arxiv_org_abs_2507_08997
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Constraints on the spread of nuclear masses in ultra-high-energy cosmic rays based on the Phase I hybrid data from the Pierre Auger Observatory
Yushkov, Alexey
High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
We present an analysis of the correlation between the depth of the maximum of air-shower profiles and the signal in water-Cherenkov stations in events registered simultaneously by the fluorescence and surface detectors of the Pierre Auger Observatory. The analysis enables us to place constraints on the spread of nuclear masses in ultra-high-energy cosmic rays with a minor impact from the experimental systematic uncertainties and uncertainties in air-shower simulations. Due to this unique feature, the correlation analysis has previously allowed us to exclude all pure and proton-helium compositions near the ankle in the cosmic-ray energy spectrum at 5$σ$ confidence level. The same property makes the correlation analysis an effective tool for testing the consistency of predictions of the post-LHC hadronic interaction models, including their latest versions such as EPOS LHC-R, QGSJet-III-01, Sibyll${}^\bigstar$ and Sibyll 2.3e. In this work, the correlation analysis using the Phase I hybrid data from the Pierre Auger Observatory is presented. The analysis uses the newest generation of hadronic interaction models and covers an extended energy range around the ankle in the cosmic-ray spectrum.
title Constraints on the spread of nuclear masses in ultra-high-energy cosmic rays based on the Phase I hybrid data from the Pierre Auger Observatory
topic High Energy Astrophysical Phenomena
High Energy Physics - Phenomenology
url https://arxiv.org/abs/2507.08997