Anomalous Air Showers and What They Reveal About Hadronic Interactions and Cosmic-ray Masses

Stijn Buitink; Vital De Henau; Sjoerd Bouma; Justin Bray; Arthur Corstanje; Edwin Dickinson; Brian Hare; Andreas Haungs; Haoning He; Jörg Hörandel; Tim Huege; Clancy James; Philipp Laub; Xingyu Li; Hermann-Josef Mathes; Katharine Mulrey; Anna Nelles; Subhadip Saha; Felix Schlüter; Olaf Scholten; Ralph Spencer; Christopher Sterpka; Karen Terveer; Satyendra Thoudam; Gia Trinh; Paulina Turekova; Darko Veberic; Keito Watanabe; Chao Zhang; Pengfei Zhang; Yi Zhang

arXiv · 2607.00135

Anomalous Air Showers and What They Reveal About Hadronic Interactions and Cosmic-ray Masses

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Abstract

The identification of the sources and acceleration mechanisms of cosmic rays require precise measurements of their mass composition. Currently, the most reliable method is to measure the atmospheric depth at which cosmic ray air showers in our atmosphere reach their maximum (\Xmax). However, the hadronic interaction properties that govern the longitudinal development of air showers are not precisely known, which is a major source of systematic uncertainty on the mass composition. SKA-Low will observe cosmic rays in the 10$^{16}$ - 10$^{18}$ eV energy range with unprecedented resolution and bandwidth. This allows for a much more detailed reconstruction of the longitudinal shower evolution, which can be used to gain better understanding of the hadronic interactions, as well as the primary mass composition. After the first interaction of the cosmic ray with an atom in an air molecule, the secondary particles still carry a significant fraction of the total energy. When one of these particle travels very far before interacting again, it produces a sub-shower that can be recognized as a secondary bump in the longitudinal profile. Simulations have demonstrated that SKA-Low can resolve such double bump profiles by virtue of its high antenna density and broad bandwidth. In this chapter, we demonstrate how double-bump showers and other anomalous longitudinal developments can be used to constrain hadronic interaction properties, and to determine the mass composition of cosmic rays in the Galactic-to-extragalactic transition region.

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Stijn Buitink, Vital De Henau, Sjoerd Bouma, Justin Bray, Arthur Corstanje, Edwin Dickinson, Brian Hare, Andreas Haungs, Haoning He, Jörg Hörandel, Tim Huege, Clancy James, Philipp Laub, Xingyu Li, Hermann-Josef Mathes, Katharine Mulrey, Anna Nelles, Subhadip Saha, Felix Schlüter, Olaf Scholten, Ralph Spencer, Christopher Sterpka, Karen Terveer, Satyendra Thoudam, Gia Trinh, Paulina Turekova, Darko Veberic, Keito Watanabe, Chao Zhang, Pengfei Zhang, Yi Zhang. 2026-06-30. Anomalous Air Showers and What They Reveal About Hadronic Interactions and Cosmic-ray Masses. https://arxiv.org/abs/2607.00135

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