Learning the Composition of Ultra High Energy Cosmic Rays

• Published in: arXiv.org
• Main Authors: Blaz Bortolato, Kamenik, Jernej F, Tammaro, Michele
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 09.12.2022
• Subjects: Atmospheric models; Augers; Composition; Cosmic ray showers; Interaction models; Physics - High Energy Astrophysical Phenomena; Physics - High Energy Physics - Phenomenology; Primary cosmic rays; Statistical inference
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2212.04760

We apply statistical inference on the Pierre Auger Open Data to discern for the first time the full mass composition of cosmic rays at different energies. Working with longitudinal electromagnetic profiles of cosmic ray showers, in particular their peaking depths \(X_{\rm max}\), we employ central moments of the \(X_{\rm max}\) distributions as features to discriminate between different shower compositions. We find that already the first few moments entail the most relevant information to infer the primary cosmic ray mass spectrum. Our approach, based on an unbinned likelihood, allows us to consistently account for sources of statistical uncertainties due to finite datasets, both measured and simulated, as well as systematic effects. Finally, we provide a quantitative comparison of different high energy hadronic interaction models available in the atmospheric shower simulation codes.