Showing 1–50 of 363 results for author: Huege, T

Observation of the Moon and Sun shadows with cosmic rays at an average energy of $\text{7}{\times}\text{10}^\text{17}\,$eV

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (324 additional authors not shown)

Abstract: Interactions of cosmic rays with the Moon and the Sun produce deficits in their arrival-direction distributions relative to an isotropic flux. Such shadows have been observed previously at energies between $10^{12}\,$eV and $10^{16}\,$eV. We report the first observation of the Moon and Sun shadows at cosmic-ray energies larger than about $10^{16}\,$eV (average energy of $7\times10^{17}\,$eV), usin… ▽ More Interactions of cosmic rays with the Moon and the Sun produce deficits in their arrival-direction distributions relative to an isotropic flux. Such shadows have been observed previously at energies between $10^{12}\,$eV and $10^{16}\,$eV. We report the first observation of the Moon and Sun shadows at cosmic-ray energies larger than about $10^{16}\,$eV (average energy of $7\times10^{17}\,$eV), using data collected by the Pierre Auger Observatory. We employ data from three detector arrays covering $3000\,\text{km}^2$, $27\,\text{km}^2$, and $2\,\text{km}^2$, with spacings of $1500\,\text{m}$, $750\,\text{m}$, and $433\,\text{m}$, respectively. The data amount to over 10.6 million events. The Moon and Sun shadows are detected with a combined significance of approximately $3σ$. These observations confirm the pointing accuracy of the Surface Detector of the Pierre Auger Observatory using celestial bodies. From the combined Sun and Moon shadows, we infer an overall angular resolution of $(0.59^{+0.15}_{-0.11})^\circ$. △ Less

Submitted 5 August, 2026; originally announced August 2026.

Comments: submitted for review

Search for active-sterile neutrino transitions using Pierre Auger Observatory data

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (326 additional authors not shown)

Abstract: We investigate the sensitivity of the Pierre Auger Observatory to physics beyond the Standard Model arising from magnetic-moment-induced transitions between active and heavy sterile neutrinos. Such dipole portal interactions can enhance neutrino-nucleon cross sections above a kinematic threshold set by the sterile neutrino mass, leading to observable modifications of neutrino detection rates at ul… ▽ More We investigate the sensitivity of the Pierre Auger Observatory to physics beyond the Standard Model arising from magnetic-moment-induced transitions between active and heavy sterile neutrinos. Such dipole portal interactions can enhance neutrino-nucleon cross sections above a kinematic threshold set by the sterile neutrino mass, leading to observable modifications of neutrino detection rates at ultrahigh energies (UHE). We estimate the impact of these interactions on both down-going and Earth-skimming neutrino detection channels, the contrasting responses of which enable discrimination between an enhanced neutrino flux and a modified interaction cross section. Using the non-observation of UHE neutrino candidates, we derive neutrino-flux-dependent constraints with 90% confidence-level on the transition magnetic moment for sterile neutrino masses in the range 1 TeV-100 TeV. Under the assumed flux scenarios, the resulting flavor-independent limits extend existing bounds into previously unexplored parameter space. △ Less

Submitted 2 August, 2026; originally announced August 2026.

Comments: 11 pages, 4 figures

Proton-air interaction properties at $\sqrt{s} \simeq 100$ TeV from shower-depth measurements with the Pierre Auger Observatory and their connection to the Muon Puzzle

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (325 additional authors not shown)

Abstract: Hybrid measurements at the Pierre Auger Observatory indicate that most high-energy hadronic interaction models underestimate the average depth of the shower maximum, $\langle X_{\max} \rangle$, at a center-of-mass energy of $\sqrt{s}=97.7 \pm 0.4^{+6.6}_{-6.2}\,\mathrm{TeV}$. In this Letter, the hadronic interaction models are shown to follow a universal relation between the predicted… ▽ More Hybrid measurements at the Pierre Auger Observatory indicate that most high-energy hadronic interaction models underestimate the average depth of the shower maximum, $\langle X_{\max} \rangle$, at a center-of-mass energy of $\sqrt{s}=97.7 \pm 0.4^{+6.6}_{-6.2}\,\mathrm{TeV}$. In this Letter, the hadronic interaction models are shown to follow a universal relation between the predicted $\langle X_{\max} \rangle$ and the mean values of variables characterizing the energy spectra of secondary particles produced in the first interaction of proton-induced air showers. Assuming the validity of these relations in Nature, we map the values of $\langle X_{\max} \rangle$ favored by Auger data into mean values of these variables. All models favor an increase in the mean elasticity and in the fraction of hadronic energy in proton--air interactions. The latter must be amplified by a factor of $2.8$ to $4.6$ to account for the muon puzzle. △ Less

Submitted 24 July, 2026; originally announced July 2026.

Comments: Submitted to Phys. Rev. Lett

Unveiling the Mysteries of Lightning: Exploring its fundamental Physical Processes with SKA-LOW

Authors: Brian M Hare, Sjoerd Bouma, Stijn Buitink, Arthur Corstanje, Steve Cummer, Joseph Dwyer, Vital De Henau, Tim Huege, Philipp Laub, Ningyu Liu, Marten A. A. Lourens, Katie Mulrey, Anna Nelles, Olaf Scholten, Chris Sterpka, Karen Terveer, Paulina Ťureková, Keito Watanabe

Abstract: Lightning is a surprisingly poorly understood phenomena. It consists of a wide variety of complex processes such as initiation, propagation, connection to ground, even emission of high-energy radiation. However, due to the extreme challenges in observing lightning at fast time scales, small spatial scales, and behind obscuring clouds, these processes are not well understood. In the past, interfero… ▽ More Lightning is a surprisingly poorly understood phenomena. It consists of a wide variety of complex processes such as initiation, propagation, connection to ground, even emission of high-energy radiation. However, due to the extreme challenges in observing lightning at fast time scales, small spatial scales, and behind obscuring clouds, these processes are not well understood. In the past, interferometers such as the LOFAR radio telescope have provided unique insight and discoveries into the physics of lightning. The new SKA-LOW being built in western Australia will provide unrivaled spectral bandwidth and sensitivity, which will be combined with high resolution resulting from large antenna baselines. We will use SKA-LOW to observe lightning in order to explore its fundamental plasma physics, such as how it initiates and propagates. SKA's high bandwidth will allow us to test how lightning emits VHF radiation, giving tremendous insight into precisely how the plasma behaves. SKA's sensitivity will allow us to explore extremely faint lightning processes, such as the very first radio emission from a lightning flash. Here, we detail the lightning physics that can be explored with SKA, as well as the observation strategy needed explore such physics. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Hare01

Report number: AASKAII/Hare01

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

Authors: 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 , et al. (6 additional authors not shown)

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 precise… ▽ More 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. △ Less

Submitted 30 June, 2026; originally announced July 2026.

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Buitink01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes

Report number: AASKAII/Buitink01

Measuring High-Energy Cosmic Particles with the SKA

Authors: Tim Huege, Katharine Mulrey, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje, Vital De Henau, Edwin Dickinson, Brian Hare, Haoning He, Jörg Hörandel, Clancy James, Philipp Laub, Xingyu Li, Marten Lourens, Hermann-Josef Mathes, Anna Nelles, Subhadip Saha, Felix Schlüter, Olaf Scholten, Ralph Spencer, Christopher Sterpka, Karen Terveer, Satyendra Thoudam, Gia Trinh , et al. (6 additional authors not shown)

Abstract: The origin of high-energy cosmic rays remain one of astrophysics' greatest unsolved mysteries. SKA-Low will be able to measure air showers initiated by cosmic rays with unprecedented precision in the PeV - EeV energy range, covering the critical transition region between Galactic and extragalactic sources. SKA-Low's densely instrumented core and broad bandwidth will allow for measurements of indiv… ▽ More The origin of high-energy cosmic rays remain one of astrophysics' greatest unsolved mysteries. SKA-Low will be able to measure air showers initiated by cosmic rays with unprecedented precision in the PeV - EeV energy range, covering the critical transition region between Galactic and extragalactic sources. SKA-Low's densely instrumented core and broad bandwidth will allow for measurements of individual air showers with a level of detail unmatched by any existing or planned detector. The depth of shower maximum, the primary mass-sensitive observable, will be reconstructed with a resolution of better than 8~g/cm$^2$, a significant improvement over existing methods. Additionally, new reconstruction methods are expected to enable full air shower reconstruction across a wide energy range, down to PeV levels. At these energies, efficient photon/hadron separation may offer an opportunity to measure PeV gamma-ray air showers. Furthermore, SKA-Low opens a window into studying high-energy hadronic interactions, including via the unique channel of anomalous air showers. This combination of measurements provides a unique opportunity to investigate the origins and physics of high-energy cosmic rays. A dedicated particle detector array will provide triggered readout of raw antenna-level voltage buffers, enabling fully commensal cosmic-ray observations alongside regular operations. We outline our science case and discuss the observational strategy, signal properties and detector design underpinning these measurements. We also summarize the accompanying book chapters, which address composition measurements in the Galactic-to-extragalactic transition region, next-generation interferometric reconstruction techniques, hadronic interaction physics through anomalous air showers, the prospects for detecting PeV gamma-rays from Galactic sources, and the related project of imaging lightning using SKA-Low. △ Less

Submitted 26 June, 2026; originally announced June 2026.

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Huege01. Advancing Astrophysics with the SKA II (AASKAII) outlines the transformative scientific advances that will be enabled by the SKA telescopes

Report number: AASKAII/Huege01

Origins of Cosmic Rays in the Galactic-extragalactic Transition Energy Range

Authors: A. Corstanje, S. Saha, S. Bouma, J. Bray, S. Buitink, V. de Henau, E. Dickinson, B. Hare, A. Haungs, H. He, J. Hörandel, T. Huege, C. James, P. Laub, X. Li, H-J. Mathes, K. Mulrey, A. Nelles, F. Schlüter, O. Scholten, R. Spencer, C. Sterpka, K. Terveer, S. Thoudam, G. Trinh , et al. (6 additional authors not shown)

Abstract: Cosmic rays arrive at Earth with energies ranging from $10^9$ to over $10^{20}$ eV. One of the open questions in high-energy cosmic ray science concerns the origin of the highest-energy cosmic rays that can be accelerated by Galactic sources, and the transition energy beyond which only extragalactic sources can provide. Measuring the mass composition gives essential information for comparing measu… ▽ More Cosmic rays arrive at Earth with energies ranging from $10^9$ to over $10^{20}$ eV. One of the open questions in high-energy cosmic ray science concerns the origin of the highest-energy cosmic rays that can be accelerated by Galactic sources, and the transition energy beyond which only extragalactic sources can provide. Measuring the mass composition gives essential information for comparing measurements to source and propagation models, both from the abundances at the source and from the maximum attainable energy which is proportional to the particle charge (and hence its mass). The highest-energy cosmic rays from the Galaxy are found in a range of $10^{16}$ to $10^{18}$ eV which is well suited for radio detection. Building on a decade of experience in measuring cosmic rays at LOFAR, we show that SKA-Low, augmented with an array of small particle detectors, is well suited to advance the field by measuring the mass composition of cosmic rays across this energy range. △ Less

Submitted 25 June, 2026; originally announced June 2026.

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Corstanje01

Report number: AASKAII/Corstanje01

Interferometric Analysis of Air-shower Radio Emission in the Near Field with an Information Field Theory Approach

Authors: Keito Watanabe, Karen Terveer, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje, Vital De Henau, Tim Huege, Edwin Dickinson, Vincent Eberle, Torsten Enßlin, Brian Hare, Haoning He, Jörg Hörandel, Clancy James, Philipp Laub, Xingyu Li, Hermann-Josef Mathes, Katharine Mulrey, Anna Nelles, Subhadip Saha, Felix Schlüter, Olaf Scholten, Ralph Spencer, Christopher Sterpka , et al. (7 additional authors not shown)

Abstract: Current reconstruction techniques for air-shower radio emission generated by cosmic rays have shown great success, having been applied to several radio detectors over the last decade. Nevertheless, they are limited by their high computational cost, simplified approximations, and signal information used for reconstruction. As such, advanced analyses are required to not only be able to perform a hol… ▽ More Current reconstruction techniques for air-shower radio emission generated by cosmic rays have shown great success, having been applied to several radio detectors over the last decade. Nevertheless, they are limited by their high computational cost, simplified approximations, and signal information used for reconstruction. As such, advanced analyses are required to not only be able to perform a holistic reconstruction of all parameters, but also to conduct near-field interferometry of the air shower. This can be achieved through Information Field Theory (IFT), an imaging reconstruction framework based on Bayesian inference that can extract all available information within the signal to infer distributions of field-like quantities. In this chapter, we highlight current novel approaches that use IFT for air shower reconstruction, and the potential of their applicability towards SKA-Low. △ Less

Submitted 25 June, 2026; originally announced June 2026.

Comments: Published in Advancing Astrophysics with the SKA II (AASKAII), 2026 (arXiv:2606.20366). Report-no:AASKAII/Watanabe01

Report number: AASKAII/Watanabe01

Using SKA-Low to Detect PeV Gamma-rays from Galactic Sources

Authors: Anna Nelles, Philipp Laub, Haoning He, Felix Schlüter, Sjoerd Bouma, Justin Bray, Stijn Buitink, Arthur Corstanje, Vital De Henau, Edwin Dickinson, Brian Hare, Jörg Hörandel, Tim Huege, Clancy James, Xingyu Li, Hermann-Josef Mathes, Katharine Mulrey, Subhadip Saha, Olaf Scholten, Ralph Spencer, Christopher Sterpka, Karen Terveer, Satyendra Thoudam, Gia Trinh, Paulina Turekova , et al. (6 additional authors not shown)

Abstract: Detecting so called PeVatrons is considered one of the prime goals of $γ$-ray astronomy. PeVatrons are astrophysical objects in the Galaxy that are sources of cosmic rays exceeding PeV ($10^{15}$ eV) energies, the highest in our Galaxy. Their nature is unknown as of now, with some candidates reaching barely above PeV energies just having been identified. Serendipitously, the energy threshold of ai… ▽ More Detecting so called PeVatrons is considered one of the prime goals of $γ$-ray astronomy. PeVatrons are astrophysical objects in the Galaxy that are sources of cosmic rays exceeding PeV ($10^{15}$ eV) energies, the highest in our Galaxy. Their nature is unknown as of now, with some candidates reaching barely above PeV energies just having been identified. Serendipitously, the energy threshold of air shower detection using radio emission, has been proven at 50 PeV. There is a case to be made that SKA-Low with its unprecedented number of antennas, can reach lower in energy, while the size of the core is sufficiently large provide a significant effective area to measure PeV fluxes. While this promises a novel angle towards understanding the cosmic ray accelerators in our Galaxy, it also would be the first detection of $γ$-ray air showers using radio emission. △ Less

Submitted 25 June, 2026; v1 submitted 24 June, 2026; originally announced June 2026.

Comments: Published in Advancing Astrophysics with the SKAII(AASKAII), 2026(arXiv:2606.20366). Report-no:AASKAII/Nelles01

Report number: AASKAII/Nelles01

Advancing Astrophysics with the SKA II

Authors: Anna Bonaldi, Tyler L. Bourke, Philippa Hartley, Tao An, Marc Audard, Olga Bayandina, Nicola Bellomo, Eleonora Bianchi, Marta Burgay, Joseph Callingham, Stefano Camera, Viviana Casasola, Virginia Cuciti, Philippa Cole, Neeraj Gupta, Catherine L. Hale, Ian Harrison, Jason Hessels, Tim Huege, Bhal Chandra Joshi, Aris Karastergiou, Dharam Lal, Adrian Liu, James Miller-Jones, S. A. Mao , et al. (23 additional authors not shown)

Abstract: Advancing Astrophysics with the SKA II (AASKAII), written by our science community, outlines the transformative scientific advances that will be enabled by the SKA telescopes. In the decade since the publication of the previous edition, telescope designs have matured, construction has commenced, and the SKA Organisation has evolved into the SKA Observatory (SKAO). At the same time, observations fr… ▽ More Advancing Astrophysics with the SKA II (AASKAII), written by our science community, outlines the transformative scientific advances that will be enabled by the SKA telescopes. In the decade since the publication of the previous edition, telescope designs have matured, construction has commenced, and the SKA Organisation has evolved into the SKA Observatory (SKAO). At the same time, observations from SKA precursor and pathfinder telescopes have provided new insights into longstanding scientific challenges while revealing entirely new phenomena. Published in advance of the first science verification campaign for the SKA Observatory, this volume looks ahead to the coming decades of discovery and innovation in radio astronomy. AASKAII spans the broad range of scientific research enabled by the SKA telescopes, SKA-Mid and SKA-Low. The contributions are organised into six thematic categories according to their scientific focus. The opening section presents overview chapters from the SKA Science Working Groups, around which our community is organised. Each overview provides the broader context that connects the contributions in this volume to the key scientific questions being pursued by their respective communities. △ Less

Submitted 8 July, 2026; v1 submitted 18 June, 2026; originally announced June 2026.

Depth of Maximum of Air-Shower Profiles above 10^17.7 eV Measured with the Fluorescence Detector of the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, M. Ahmed, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato , et al. (336 additional authors not shown)

Abstract: We present measurements of the depth of shower maximum, Xmax, for cosmic-ray-induced extensive air showers recorded by the fluorescence detector of the Pierre Auger Observatory over 17 years. The data set covers primary energies from 10^17.7 eV to beyond 10^19.6 eV. With improved event reconstruction and an exposure 2.4 times larger than in our previous analysis, this work confirms and refines our… ▽ More We present measurements of the depth of shower maximum, Xmax, for cosmic-ray-induced extensive air showers recorded by the fluorescence detector of the Pierre Auger Observatory over 17 years. The data set covers primary energies from 10^17.7 eV to beyond 10^19.6 eV. With improved event reconstruction and an exposure 2.4 times larger than in our previous analysis, this work confirms and refines our conclusions on the mass composition at ultra-high energies. The energy evolution of the mean Xmax exhibits a pronounced break at around 10^18.4 eV, providing direct, model-independent evidence for a change in the evolution of the mass composition. Independently, the observed decrease of the Xmax fluctuations with energy indicates a transition toward a heavier and less diverse primary mass composition. No statistically significant declination dependence of the Xmax distributions is observed within the exposure of the Observatory, indicating an isotropic mass composition. The mean and standard deviation of the Xmax distributions, interpreted with air-shower simulations, yield the energy dependence of the average and variance of the logarithmic mass of cosmic rays arriving at Earth. Furthermore, energy-dependent fractional abundances of four representative primary-mass groups (p, He, CNO, Fe) are obtained by fitting the observed Xmax distributions in each energy bin with a weighted sum of elemental templates. These results provide strong evidence against a long-standing assumption that ultra-high-energy cosmic rays are predominantly protons: above ~10^18.4 eV, the average cosmic-ray mass increases, accompanied by a steadily decreasing diversity in the elemental composition. △ Less

Submitted 12 May, 2026; originally announced May 2026.

Comments: 28 pages, 23 figures, submitted to PRD

CORSIKA 8: A General Framework for Particle Cascade Simulations

Authors: J. M. Alameddine, J. Albrecht, A. A Alves Jr., J. Ammerman-Yebra, L. Arrabito, D. Baack, A. Coleman, C. Deaconu, H. Dembinski, D. Elsässer, R. Engel, A. Faure, A. Ferrari, C. Gaudu, C. Glaser, M. Gottowik, D. Heck, T. Huege, K. H. Kampert, N. Karastathis, J. Lazar, L. Nellen, D. Parello, T Pierog, R. Prechelt , et al. (12 additional authors not shown)

Abstract: The simulation of extensive air showers and particle cascades in general is a cornerstone of modern astroparticle physics. For more than two decades, CORSIKA, currently in version 7, has been one of the most widely used tools for this purpose. However, its architecture reflects design constraints of an earlier computing era, as well as increasingly limiting extensibility, maintainability, and adap… ▽ More The simulation of extensive air showers and particle cascades in general is a cornerstone of modern astroparticle physics. For more than two decades, CORSIKA, currently in version 7, has been one of the most widely used tools for this purpose. However, its architecture reflects design constraints of an earlier computing era, as well as increasingly limiting extensibility, maintainability, and adaptability to modern experimental requirements. CORSIKA 8 is a complete redesign of the original CORSIKA code, implemented in modern C++ and based on contemporary software engineering principles. It introduces a modular and extensible simulation framework with explicit handling of units, flexible geometry, and environment descriptions. In this paper, we present the design philosophy and core architecture of CORSIKA 8, describe the implementation of electromagnetic and hadronic shower physics, and validate air shower simulations against CORSIKA 7. The results demonstrate good agreement at the few-percent level for key observables, confirming the physics fidelity of CORSIKA 8. We also showcase new use cases that were beyond the capabilities of version 7, such as the simulation of cross-media showers and particle cascades in ice, including radio-signal propagation △ Less

Submitted 8 July, 2026; v1 submitted 2 April, 2026; originally announced April 2026.

Comments: 29 pages, 21 figures

Journal ref: Astroparticle Physics 182 (2026) 103265

A Particle Detector Array deployed to the Murchison Widefield Array in the Murchison Radio-astronomy Observatory

Authors: J. E. Dickinson, J. D. Bray, D. Kenney, T. Booler, J. Edgley, D. Emrich, A. Forouzan, T. Gould, A. McPhail, P. Roberts, R. E. Spencer, L. Verduyn, R. Watson, A. Williams, K. Grainge, A. Haungs, T. Huege, C. W. James, S. J. Tingay

Abstract: We report the design and functionality of the Murchison Widefield Array Particle Detector Array (MWA PDA), an array of eight particle scintillation detectors deployed to Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory (MRO). The purpose of the instrument is to identify cosmic ray extensive air showers (EAS) occurring over the core of the MWA radio telescope, and generate a t… ▽ More We report the design and functionality of the Murchison Widefield Array Particle Detector Array (MWA PDA), an array of eight particle scintillation detectors deployed to Inyarrimanha Ilgari Bundara, the Murchison Radio-astronomy Observatory (MRO). The purpose of the instrument is to identify cosmic ray extensive air showers (EAS) occurring over the core of the MWA radio telescope, and generate a trigger to allow radio data on the event to be captured and analysed. The system also acts as a pathfinder for a much larger instrument to be deployed in the core of the low-frequency component of the Square Kilometre Array, SKA-Low, by the SKA's ultra-high-energy particles science working group. Here, we describe the instrument and associated infrastructure, which has been verified to comply with the strict radio-frequency emissions requirements of the MRO, and was deployed in November 2024. We present calibration data, which demonstrates the ability of each detector to identify individual atmospheric muons at the expected rate, and we characterise the temperature dependence of the system. We describe a sample of 35,500 EAS identified using multi-detector coincidence over a 13-day period, and show how the detector data can be used to reconstruct the arrival directions and approximate energies of these events. We conclude that the PDA can reliably trigger on and reconstruct EAS contained within the $\sim 103 \times 90$ m$^2$ core region, arriving within 20$^{\circ}$ of zenith, at primary cosmic ray energies above $\sim 4$ PeV. We have also verified that the detector array can generate triggers, allowing the capture of radio data from the MWA correlator for offline analysis. △ Less

Submitted 27 February, 2026; originally announced March 2026.

Comments: 16 pages, 21 figures, 1 table

A Bayesian Method for Air-Shower Reconstruction using Information Field Theory

Authors: Karen Terveer, Sjoerd Bouma, Stijn Buitink, Arthur Corstanje, Vital De Henau, Vincent Eberle, Torsten A. Enßlin, Philipp Frank, Tim Huege, Philipp Laub, Katharine Mulrey, Anna Nelles, Simon Strähnz, Satyendra Thoudam, Keito Watanabe

Abstract: The radio detection of extensive air showers provides a powerful method for studying the origin of high-energy cosmic rays. The Low-Frequency Array (LOFAR) offers unprecedentedly detailed measurements of the radio emission footprint. However, fully exploiting this information requires advanced reconstruction techniques. In this paper, we introduce a novel framework for air shower reconstruction ba… ▽ More The radio detection of extensive air showers provides a powerful method for studying the origin of high-energy cosmic rays. The Low-Frequency Array (LOFAR) offers unprecedentedly detailed measurements of the radio emission footprint. However, fully exploiting this information requires advanced reconstruction techniques. In this paper, we introduce a novel framework for air shower reconstruction based on Bayesian inference and Information Field Theory (IFT). Our method is built on a fully differentiable forward model of the radio signal, which incorporates a physical emission parameterization and a precise wavefront model. Additionally, we augment this physical model with Gaussian processes to account for systematic uncertainties in both the signal fluence and arrival timing. By leveraging gradient information, our approach enables efficient (three orders of magnitude acceleration w.r.t.\ the legacy method) and robust inference of the underlying physical shower parameters, such as primary energy and the depth of shower maximum, $X_\text{max}$. This work provides not only point estimates but also a rigorous quantification of uncertainties. We achieve a resolution in $X_\text{max}$ of $25\,\mathrm{g/cm^2}$ and a radiation energy resolution of $12\%$ on simulations for LOFAR. △ Less

Submitted 2 April, 2026; v1 submitted 23 February, 2026; originally announced February 2026.

Comments: 19 pages, 11 figures

Journal ref: Astroparticle Physics 179 (2026), 103241

Bounds on Lorentz invariance violation from muon fluctuations at the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (335 additional authors not shown)

Abstract: Quantum gravity theories often modify spacetime symmetries. In particular, Lorentz invariance may be violated when approaching the Planck scale. Although the scales at which interactions occur in extensive air showers induced by ultra-high-energy cosmic rays in the atmosphere are many orders of magnitude below the Planck scale, these violations might still be observable. In this work, the fluctuat… ▽ More Quantum gravity theories often modify spacetime symmetries. In particular, Lorentz invariance may be violated when approaching the Planck scale. Although the scales at which interactions occur in extensive air showers induced by ultra-high-energy cosmic rays in the atmosphere are many orders of magnitude below the Planck scale, these violations might still be observable. In this work, the fluctuations in the number of muons in the extensive air showers measured at the Pierre Auger Observatory are exploited, for the first time, to constrain Lorentz invariance violations. The bounds derived in the hadronic sector are the strongest ever obtained, and do not rely on assumptions about the mass composition of ultra-high-energy cosmic rays. The fluctuations in the number of muons constitute a new and powerful observable to further explore Lorentz invariance in a region of the parameter space not accessible to other observables. △ Less

Submitted 4 June, 2026; v1 submitted 16 February, 2026; originally announced February 2026.

Comments: 15 pages, 9 figures Accepted for publication on PRL

Search for ultra-high energy neutrons from Galactic sources with the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (335 additional authors not shown)

Abstract: Deflections in the propagation of charged ultra-high-energy cosmic rays (UHECRs) caused by magnetic fields make the identification of their sources challenging. On the other hand, the arrival directions at Earth of neutrons point directly to their origin. The emission of UHECRs from a source is expected to be accompanied by the production of neutrons in its vicinity through interactions with ambie… ▽ More Deflections in the propagation of charged ultra-high-energy cosmic rays (UHECRs) caused by magnetic fields make the identification of their sources challenging. On the other hand, the arrival directions at Earth of neutrons point directly to their origin. The emission of UHECRs from a source is expected to be accompanied by the production of neutrons in its vicinity through interactions with ambient matter and radiation. Since free neutrons travel a mean distance $d/\text{kpc}=9.2(E/\text{EeV})$ before decaying, a neutron flux in the EeV range could be detected on Earth from sources of UHECRs in our Galaxy. Using cosmic-ray data from the Phase\,I of the Surface Detector of the Pierre Auger Observatory, we search for neutron fluxes from Galactic candidate sources. We select more than 1000 objects of astrophysical interest, stacking them into target sets. The targets all have declinations within the exposure of the Observatory, ranging from $-90^\circ$ up to $+45^\circ$ for energies above 1 EeV (and up to $+20^\circ$ for energies down to 0.1 EeV). Given that a neutron air shower is indistinguishable from a proton one, there is a significant background due to cosmic rays. A neutron flux from the direction of a candidate source would be identified by a celestial density of events that significantly exceeds the expected density of cosmic rays for that direction. No significant excess is found at any tested target direction, and an upper limit on the neutron flux is calculated for each candidate source. △ Less

Submitted 2 February, 2026; originally announced February 2026.

Comments: 13 pages, 6 tables, 1 figure

Neural Network for Simulating Radio Emission from Extensive Air Showers

Authors: Pranav Sampathkumar, Tim Huege, Andreas Haungs, Ralph Engel

Abstract: Cosmic ray shower detection using large radio arrays has gained significant traction in recent years. With massive improvements in signal modelling and microscopic simulations, the analysis of incoming events is still severely limited by the simulation cost of radio emission to interpret the data. In this work, we show that a neural network can be used for simulating such radio pulses. This work s… ▽ More Cosmic ray shower detection using large radio arrays has gained significant traction in recent years. With massive improvements in signal modelling and microscopic simulations, the analysis of incoming events is still severely limited by the simulation cost of radio emission to interpret the data. In this work, we show that a neural network can be used for simulating such radio pulses. This work serves as a proof of concept that simple neural networks can be used for emergent deterministic macroscopic phenomena of microscopic simulations. We also demonstrate how such a neural network can be used for the physics use case of $X_\mathrm{max}$ reconstruction, while retaining comparable resolution to using full Monte-Carlo simulations for radio emission. Code available at https://anonymous.4open.science/r/radio_nn-21BF/. △ Less

Submitted 24 December, 2025; originally announced December 2025.

Comments: Thirty-Ninth Annual Conference on Neural Information Processing Systems (NeurIPS 2025). arXiv admin note: substantial text overlap with arXiv:2507.07713

Long-term calibration and validation of stability of the Auger Engineering Radio Array using the diffuse Galactic radio emission

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, Y. Balibrea, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (334 additional authors not shown)

Abstract: The Auger Engineering Radio Array (AERA) measures radio emission from high-energy extensive air showers. Consisting of 153 autonomous radio-detector stations spread over $17$\,km$^2$, it detects radio waves in the frequency range of $30$ to $80$\,MHz. Accurate characterization of the detector response is crucial for proper interpretation of the collected data. Previously, this was achieved through… ▽ More The Auger Engineering Radio Array (AERA) measures radio emission from high-energy extensive air showers. Consisting of 153 autonomous radio-detector stations spread over $17$\,km$^2$, it detects radio waves in the frequency range of $30$ to $80$\,MHz. Accurate characterization of the detector response is crucial for proper interpretation of the collected data. Previously, this was achieved through laboratory measurements of the analog chain and simulations and measurements of the antenna's directional response. In this paper, we perform an absolute calibration using the continuously monitored sidereal modulation of the diffuse Galactic radio emission. Calibration is done by comparing the average frequency spectra recorded by the stations with predictions from seven different models of the full radio sky, accounting for the system response, which includes the antenna, filters, and amplifiers. The analysis of the calibration constants over a period of seven years shows no relevant and no significant ageing effect in the AERA antennas. This result confirms the long-term stability of the detector stations and demonstrates the possibility for a radio detector to effectively monitor ageing effects of other detectors operating over extended periods. △ Less

Submitted 3 December, 2025; originally announced December 2025.

Comments: 20 pages, 9 figures, 2 tables

Quasi-constant time gap in multiple rings of elves

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, G. A. Anastasi, L. Anchordoqui, B. Andrada, L. Andrade Dourado, S. Andringa, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato , et al. (337 additional authors not shown)

Abstract: We present evidence that the time delay between the multiple rings of elves is not caused by the ground reflection of the electromagnetic pulse produced by intracloud lightning. To investigate temporal differences of multi-elves, we analyzed data from four storms occurring at various times and distances from the Pierre Auger Observatory in Malargüe, Argentina. The Auger fluorescence detector's hig… ▽ More We present evidence that the time delay between the multiple rings of elves is not caused by the ground reflection of the electromagnetic pulse produced by intracloud lightning. To investigate temporal differences of multi-elves, we analyzed data from four storms occurring at various times and distances from the Pierre Auger Observatory in Malargüe, Argentina. The Auger fluorescence detector's high temporal resolution of 100 ns enabled the frequent observation of multi-elves, accounting for approximately 23% of the events. By examining the traces of 70 double and 24 triple elves, we demonstrate that the time delay between the rings remains relatively constant regardless of the arc distance to the lightning. These results deviate from the trend expected from the electromagnetic pulse (EMP) ground reflection model, which predicts a decreasing time delay with increasing arc distance from an intracloud lightning at a given height. The first emission ring is due to a direct path of the EMP to the ionosphere, with the reflected EMP creating the second ring. Simulations conducted with this model demonstrate that short energetic in-cloud pulses can generate four-peak elves, and a temporal resolution of at least 25 $μ$s is required to separate them. Therefore, temporal resolution is crucial in the study of multi-elves. Our observations in the Córdoba province, central Argentina, indicate that the current understanding of the mechanism generating these phenomena may be incomplete, and further studies are needed to assess whether multi-elves are more likely related to the waveform shape of the lightning than to its altitude. △ Less

Submitted 7 November, 2025; originally announced November 2025.

Journal ref: Published in Earth and Space Science 12 (2025) e2025EA004321

Investigating double bump air showers with the SKA-Low

Authors: V. De Henau, S. Bouma, J. Bray, S. Buitink, A. Corstanje, M. Desmet, E. Dickinson, L. van Dongen, B. Hare, H. He, J. R. Hörandel, T. Huege, C. W. James, M. Jetti, P. Laub, H. -J. Mathes, K. Mulrey, A. Nelles, O. Scholten, C. Sterpka, S. ter Veen, K. Terveer, P. Turekova, T. N. G. Trinh, S. Saha , et al. (8 additional authors not shown)

Abstract: Double-bump showers are a rare class of extensive air showers (EAS) predicted by Monte Carlo simulations. They occur when a high-energy secondary particle, the leading particle, travels significantly farther than the rest, creating a distinct double-peaked longitudinal profile. So far, no experiment has been able to directly detect these showers. The unique radio footprint of double-bump showers,… ▽ More Double-bump showers are a rare class of extensive air showers (EAS) predicted by Monte Carlo simulations. They occur when a high-energy secondary particle, the leading particle, travels significantly farther than the rest, creating a distinct double-peaked longitudinal profile. So far, no experiment has been able to directly detect these showers. The unique radio footprint of double-bump showers, characterized by multiple Cherenkov rings, provides a way to reconstruct longitudinal profiles from radio observations. With its dense antenna array and broad frequency range, the Square Kilometer Array Observatory (SKAO) will be the first experiment capable of detecting these features, offering a new opportunity to probe hadronic interactions and constrain particle cross sections at high energies. In our analysis, we simulate the EAS using CORSIKA with the CoREAS plugin for radio. We developed a new method based on the Akaike information criterion to identify double bump showers in simulations by analyzing their longitudinal profiles. Then we investigate the prevalence of these double bump showers across different cosmic ray primary particles and various hadronic interaction models. We create a skeleton of the EAS which consists of all the particles with at least $1\%$ of the primary energy, allowing us to confirm the leading particle hypothesis and track shower development following these particles. This will enable us to relate the attributes of the leading particle to measurable parameters. Depending on the exact shower properties, the radio footprint of a double bump shower can create a complex interference pattern, consisting of multiple rings. From this information, the longitudinal profiles can be extracted. SKA due to its dense antenna array and frequency range will be the first experiment able to observe these double bump showers in detail. △ Less

Submitted 15 October, 2025; originally announced October 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025). 9 pages, 6 figures

Journal ref: PoS(ICRC2025)236

Towards the Giant Radio Array for Neutrino Detection (GRAND): the GRANDProto300 and GRAND@Auger prototypes

Authors: GRAND Collaboration, Jaime Álvarez-Muniz, Rafael Alves Batista, Aurélien Benoit-Lévy, Teresa Bister, Martina Bohacova, Mauricio Bustamante, Washington Carvalho, Yiren Chen, LingMei Cheng, Simon Chiche, Jean-Marc Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zigao Dai, Rogerio M. de Almeida, Beatriz de Errico, João R. T. de Mello Neto, Krijn D. de Vries, Valentin Decoene, Peter B. Denton, Bohao Duan, Kaikai Duan, Ralph Engel, William Erba , et al. (96 additional authors not shown)

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of Ultra-High-Energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interactions like gamma rays and neutrinos. The GRAND Collaboration plans to achieve this using large a… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of Ultra-High-Energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interactions like gamma rays and neutrinos. The GRAND Collaboration plans to achieve this using large arrays of radio antennas that look for the radio signals emitted by the air showers initiated by the interactions of the UHE particles in the atmosphere. Since 2023, three small-scale prototype GRAND arrays have been in operation: GRAND@Nançay in France, GRAND@Auger in Argentina, and GRANDProto300 in China. Together, their goal is to validate the detection principle of GRAND under prolonged field conditions, achieving efficient, autonomous radio-detection of air showers. We describe the hardware, software, layout, and operation of the GRAND prototypes. Using their data, we show a first characterization of the local electromagnetic environment of each site and a measurement of the Galactic synchrotron emission. Despite challenges, the successful operation of the prototypes confirms that the GRAND instrumentation is apt to address the goals of the experiment and lays the groundwork for its ensuing stages. △ Less

Submitted 24 February, 2026; v1 submitted 25 September, 2025; originally announced September 2025.

Comments: 30 pages, 16 figures, 2 tables

Journal ref: IOP Publishing, 21 (2026) 02

Measuring the locations and properties of VHF sources emitted from an aircraft flying through high clouds

Authors: Olaf Scholten, Marten Lourens, Stijn Buitink, Steve Cummer, Joe Dwyer, Brian M. Hare, Tim Huege, Ningyu Liu, Katie Mulrey, Anna Nelles, Chris Sterpka, T. N. Gia Trinh, Paulina Turekova, Sander ter Veen

Abstract: We show that it is possible to locate the few places on the body of an airplane, while it is flying through high clouds, from which broad-band, pulsed, radiation is emitted at Very High Frequency (VHF) radio frequencies. This serendipitous discovery was made whilst imaging a lightning flash using the Low-Frequency Array (LOFAR). This observation provides insights into the way the airplane sheds th… ▽ More We show that it is possible to locate the few places on the body of an airplane, while it is flying through high clouds, from which broad-band, pulsed, radiation is emitted at Very High Frequency (VHF) radio frequencies. This serendipitous discovery was made whilst imaging a lightning flash using the Low-Frequency Array (LOFAR). This observation provides insights into the way the airplane sheds the electrical charge it acquires when flying through clouds. Furthermore, this observation allowed us to test and improve the precision and accuracy for our lightning observation techniques. Our new results indicate that with the improved procedure the location precision for strong pulses is better than 50~cm, with the orientation of linear polarization being accurate to within 25$^\circ$. For the present case of a Boeing 777-300ER, VHF emissions were observed exclusively associated with the two engines, as well as a specific spot on the tail. Despite the aircraft flying through clouds at an altitude of 8~km, we did not detect any emissions from electrostatic wicks. △ Less

Submitted 20 September, 2025; originally announced September 2025.

Comments: Under review with Nature Communications

Journal ref: Nat Commun 16, 10572 (2025)

Road map for the tuning of hadronic interaction models with accelerator-based and astroparticle data

Authors: Johannes Albrecht, Julia Becker Tjus, Noah Behling, Jiří Blažek, Marcus Bleicher, Julian Boelhauve, Lorenzo Cazon, Ruben Conceição, Hans Dembinski, Luca Dietrich, Jan Ebr, Jan Ellbracht, Ralph Engel, Anatoli Fedynitch, Max Fieg, Maria Garzelli, Chloé Gaudu, Giacomo Graziani, Pascal Gutjahr, Andreas Haungs, Tim Huege, Karolin Hymon, Mirco Hünnefeld, Karl-Heinz Kampert, Leonora Kardum , et al. (30 additional authors not shown)

Abstract: In high-energy and astroparticle physics, event generators play an essential role, even in the simplest data analyses. As analysis techniques become more sophisticated, e.g. based on deep neural networks, their correct description of the observed event characteristics becomes even more important. Physical processes occurring in hadronic collisions are simulated within a Monte Carlo framework. A ma… ▽ More In high-energy and astroparticle physics, event generators play an essential role, even in the simplest data analyses. As analysis techniques become more sophisticated, e.g. based on deep neural networks, their correct description of the observed event characteristics becomes even more important. Physical processes occurring in hadronic collisions are simulated within a Monte Carlo framework. A major challenge is the modeling of hadron dynamics at low momentum transfer, which includes the initial and final phases of every hadronic collision. QCD-inspired phenomenological models used for these phases cannot guarantee completeness or correctness over the full phase space. These models usually include parameters which must be tuned to suitable experimental data. Until now, event generators have been developed and tuned mainly on the basis of data from high-energy physics experiments at accelerators. The wealth of data available from the latest generation of astroparticle experiments has not yet been fully exploited, and in many cases is not satisfactorily described. Both kinds of data sets are complementary as astroparticle experiments provide sensitivity especially to hadrons produced nearly parallel to the collision axis and cover center-of-mass energies up to several hundred TeV, well beyond those reached at colliders so far. In this report, we provide an overview of state-of-the-art event generators and their tuning, including the most relevant inputs from high-energy accelerator and astroparticle experiments. We present a road map that shows, for the first time, how the unified tuning of event generators with accelerator-based and astroparticle data can be performed. △ Less

Submitted 25 September, 2025; v1 submitted 29 August, 2025; originally announced August 2025.

Comments: 64 pages, 6 figures, 6 tables, submitted for publication in Nature Reviews Physics

Cosmic ray energy spectra derived from KASCADE-Grande data using post-LHC hadronic interaction models

Authors: D. Kang, J. C. Arteaga-Velázquez, M. Bertaina, A. Chiavassa, A. L. Colmenero-César, K. Daumiller, V. de Souza, R. Engel, A. Gherghel-Lascu, C. Grupen, A. Haungs, J. R. Hörandel, T. Huege, K. -H. Kampert, K. Link, H. J. Mathes, S. Ostapchenko, T. Pierog, D. Rivera-Rangel, M. Roth, H. Schieler, F. G. Schröder, O. Sima, A. Weindl, J. Wochele , et al. (1 additional authors not shown)

Abstract: KASCADE-Grande was dedicated to measuring the energy spectrum and mass composition of cosmic rays in the energy range of 10 PeV to 1 EeV. We observed a knee-like structure in the heavy mass component at around 100 PeV and an ankle-like structure in the light component. In this contribution, we present updated energy spectra based on shower size measurements, using the post-LHC hadronic models QGSJ… ▽ More KASCADE-Grande was dedicated to measuring the energy spectrum and mass composition of cosmic rays in the energy range of 10 PeV to 1 EeV. We observed a knee-like structure in the heavy mass component at around 100 PeV and an ankle-like structure in the light component. In this contribution, we present updated energy spectra based on shower size measurements, using the post-LHC hadronic models QGSJet-II-04, EPOS-LHC, and SIBYLL 2.3d, including accounting for shower-to-shower fluctuations. In addition, the newly released EPOS-LHC-R model is tested for the first time with KASCADE-Grande. We will compare and discuss the results obtained using the different hadronic interaction models. △ Less

Submitted 29 August, 2025; originally announced August 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC2025)

Report number: PoS(ICRC2025)297

A novel approach for air shower profile reconstruction with dense radio antenna arrays using Information Field Theory

Authors: K. Watanabe, S. Bouma, J. D. Bray, S. Buitink, A. Corstanje, V. De Henau, M. Desmet, E. Dickinson, L. van Dongen, T. A. Enßlin, B. Hare, H. He, J. R. Hörandel, T. Huege, C. W. James, M. Jetti, P. Laub, H. J. Mathes, K. Mulrey, A. Nelles, S. Saha, O. Scholten, S. Sharma, R. E. Spencer, C. Sterpka , et al. (10 additional authors not shown)

Abstract: Reconstructing the longitudinal profile of extensive air showers, generated from the interaction of cosmic rays in the Earth's atmosphere, is crucial to understanding their mass composition, which in turn provides valuable insight on their possible sources of origin. Dense radio antenna arrays such as the LOw Frequency ARray (LOFAR) telescope as well as the upcoming Square Kilometre Array Observat… ▽ More Reconstructing the longitudinal profile of extensive air showers, generated from the interaction of cosmic rays in the Earth's atmosphere, is crucial to understanding their mass composition, which in turn provides valuable insight on their possible sources of origin. Dense radio antenna arrays such as the LOw Frequency ARray (LOFAR) telescope as well as the upcoming Square Kilometre Array Observatory (SKAO) are ideal instruments to explore the potential of air shower profile reconstruction, as their high antenna density allows cosmic ray observations with unprecedented accuracy. However, current analysis approaches can only recover $X_\mathrm{max}$, the atmospheric depth at shower maximum, and heavily rely on computationally expensive simulations. As such, it is ever more crucial to develop new analysis approaches that can perform a full air shower profile reconstruction efficiently. In this work, we develop a novel framework to reconstruct the longitudinal profile of air showers using measurements from radio detectors with Information Field Theory (IFT), a state-of-the-art reconstruction framework based on Bayesian inference. Through IFT, we are able to exploit all available information in the signal (amplitude, phase, and pulse shape) at each antenna position simultaneously and explicitly utilise models that are motivated through our current understanding of air shower physics. We verify our framework on simulated datasets prepared for LOFAR, showcasing that we can not only reconstruct the air shower profile with uncertainties in each atmospheric depth bin but also recover the reconstructed trace at each antenna position. Our framework demonstrates that radio measurements with dense antenna layouts such as LOFAR and SKAO have the capability to go beyond reconstruction of $X_\mathrm{max}$ and will thus aid in our understanding of the mass composition of cosmic rays. △ Less

Submitted 6 August, 2025; originally announced August 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025). 9 pages, 4 figures

Journal ref: PoS(ICRC2025)436

The Pierre Auger Observatory: Contributions to the 39th International Cosmic Ray Conference (ICRC 2025)

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, L. Anchordoqui, B. Andrada, L. Andrade Dourado, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, A. Baluta, F. Barbato, A. Bartz Mocellin , et al. (330 additional authors not shown)

Abstract: The Pierre Auger Observatory, located in La Pampa Amarilla, Argentina, has been continuously acquiring data since 2004. It comprises a surface detector array covering 3,000 km$^2$ and 27 fluorescence telescopes, designed to detect extensive air showers initiated by ultra-high-energy cosmic rays. An upgrade to the Observatory was commissioned in 2024, enhancing the existing water-Cherenkov detector… ▽ More The Pierre Auger Observatory, located in La Pampa Amarilla, Argentina, has been continuously acquiring data since 2004. It comprises a surface detector array covering 3,000 km$^2$ and 27 fluorescence telescopes, designed to detect extensive air showers initiated by ultra-high-energy cosmic rays. An upgrade to the Observatory was commissioned in 2024, enhancing the existing water-Cherenkov detectors with additional radio antennas, surface scintillator detectors, and a buried scintillator array. This compilation of contributions to the 39th International Cosmic Ray Conference, held in Geneva, Switzerland (July 15-24, 2025), presents recent results from the Pierre Auger Collaboration, addressing a wide range of fundamental questions in astroparticle physics. The included papers cover measurements of the energy spectrum, mass composition, and arrival directions of ultra-high-energy cosmic rays, investigations of hadronic interactions in extensive air showers, and searches for ultra-high-energy photons and neutrinos. Additional topics include radio detection techniques, solar-related phenomena, and atmospheric events such as ELVES and TGFs. The list also contains first results and performance evaluations of the upgraded detectors, AugerPrime, along with reports on outreach and social engagement initiatives conducted by the Collaboration. △ Less

Submitted 23 October, 2025; v1 submitted 18 July, 2025; originally announced July 2025.

Information Field Theory based Event Reconstruction for Cosmic Ray Radio Detectors

Authors: Simon Strähnz, Tim Huege, Torsten Enßlin, Karen Terveer, Anna Nelles

Abstract: Detection of extensive air showers with radio antennas is an appealing technique in cosmic ray physics. However, because of the high level of measurement noise, current reconstruction methods still leave room for improvement. Furthermore, reconstruction efforts typically focus only on a single aspect of the signal, such as the energy fluence or arrival time. Bayesian inference is then a natural ch… ▽ More Detection of extensive air showers with radio antennas is an appealing technique in cosmic ray physics. However, because of the high level of measurement noise, current reconstruction methods still leave room for improvement. Furthermore, reconstruction efforts typically focus only on a single aspect of the signal, such as the energy fluence or arrival time. Bayesian inference is then a natural choice for a holistic approach to reconstruction, yet, this problem would be ill-posed, since the electric field is a continuous quantity. Information Field Theory provides the solution for this by providing a statistical framework to deal with discretised fields in the continuum limit. We are currently developing models for this novel approach to reconstructing extensive air showers. The model described here is based on the best current understanding of the emission mechanisms: It uses parametrisations of the lateral signal strength distribution, charge-excess contribution and spectral shape. Shower-to-shower fluctuations and narrowband RFI are modelled using Gaussian processes. Combined with a detailed detector description, this model can infer not only the electric field, but also the shower geometry, electromagnetic energy and position of shower maximum. Another big achievement of this approach is its ability to naturally provide uncertainties for the reconstruction, which has been shown to be difficult in more traditional methods. With such an open framework and robust computational methods based in Information Field Theory, it will also be easy to incorporate new insights and additional data, such as timing distributions or particle detector data, in the future. This approach has a high potential to exploit the full information content of a complex detector with rigorous statistical methods, in a way that directly includes domain knowledge. △ Less

Submitted 14 July, 2025; originally announced July 2025.

The Giant Radio Array for Neutrino Detection (GRAND) Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC 2025)

Authors: Jaime Álvarez-Muñiz, Rafael Alves Batista, Aurélien Benoit-Lévy, Teresa Bister, Martina Bohacova, Mauricio Bustamante, Washington Carvalho Jr., Yiren Chen, LingMei Cheng, Simon Chiche, Jean-Marc Colley, Pablo Correa, Nicoleta Cucu Laurenciu, Zigao Dai, Rogerio M. de Almeida, Beatriz de Errico, João R. T. de Mello Neto, Krijn D. de Vries, Valentin Decoene, Peter B. Denton, Bohao Duan, Kaikai Duan, Ralph Engel, William Erba, Yizhong Fan , et al. (113 additional authors not shown)

Abstract: The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned observatory of ultra-high-energy particles of cosmic origin, with energies in excess of 100 PeV. GRAND uses large surface arrays of antennas to look for the radio emission from extensive air showers that are triggered by the interaction of ultra-high-energy cosmic rays, gamma rays, and neutrinos in the atmosphere or underground.… ▽ More The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned observatory of ultra-high-energy particles of cosmic origin, with energies in excess of 100 PeV. GRAND uses large surface arrays of antennas to look for the radio emission from extensive air showers that are triggered by the interaction of ultra-high-energy cosmic rays, gamma rays, and neutrinos in the atmosphere or underground. In particular, for ultra-high-energy neutrinos, the future final phase of GRAND aims to be sensitive enough to detect them in spite of their plausibly tiny flux. Three prototype GRAND radio arrays have been in operation since 2023: GRANDProto300, in China, GRAND@Auger, in Argentina, and GRAND@Nançay, in France. Their goals are to field-test the GRAND detection units, understand the radio background to which they are exposed, and develop tools for diagnostic, data gathering, and data analysis. This list of contributions to the 39th International Cosmic Ray Conference (ICRC 2025) presents an overview of GRAND, in its present and future incarnations, and a first look at data collected by GRANDProto300 and GRAND@Auger, including the first cosmic-ray candidates detected by them. △ Less

Submitted 13 July, 2025; originally announced July 2025.

Comments: Note: To access the list of contributions, please follow the "HTML" link that can be found on the arXiv page

The IceCube-Gen2 Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC2025)

Authors: R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, G. Anton, C. Argüelles, Y. Ashida, S. Athanasiadou, J. Audehm, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., M. Baricevic, S. W. Barwick, V. Basu, R. Bay, J. Becker Tjus, P. Behrens , et al. (443 additional authors not shown)

Abstract: IceCube-Gen2 is a planned next-generation neutrino observatory at the South Pole that builds upon the successful design of IceCube. Integrating two complementary detection technologies for neutrinos, optical and radio Cherenkov emission, in combination with a surface array for cosmic-ray air shower detection, IceCube-Gen2 will cover a broad neutrino energy range from MeV to EeV. This index of cont… ▽ More IceCube-Gen2 is a planned next-generation neutrino observatory at the South Pole that builds upon the successful design of IceCube. Integrating two complementary detection technologies for neutrinos, optical and radio Cherenkov emission, in combination with a surface array for cosmic-ray air shower detection, IceCube-Gen2 will cover a broad neutrino energy range from MeV to EeV. This index of contributions to the 39th International Cosmic Ray Conference in Geneva, Switzerland (July 15-24, 2025) describes research and development efforts for IceCube-Gen2. Included are summaries of the design, status, and sensitivity of the IceCube-Gen2 optical, surface, and radio components; performance studies of next-generation surface detectors and in-ice optical sensors; advanced reconstruction techniques of cosmic-ray air showers and neutrino events; sustainability and environmental impact; and sensitivity studies of astrophysical neutrino fluxes and cosmic-ray physics. Contributions related to IceCube and the scheduled IceCube Upgrade are available in a separate collection. △ Less

Submitted 21 July, 2025; v1 submitted 11 July, 2025; originally announced July 2025.

Comments: To access the list of contributions, please follow the "HTML" link. Links to individual contributions will fill in as authors upload their material. See arXiv:2507.08666 for all IceCube contributions

Determination of the energy scale of cosmic ray measurements using the Auger Engineering Radio Array

Authors: Tim Huege

Abstract: The accurate determination of the absolute energy scale in cosmic ray measurements is both a challenging and fundamentally important task. We present how measurements of radio pulses from extensive air showers with the Auger Engineering Radio Array, combined with per-event simulations of radio emission using the CoREAS extension of CORSIKA, allow us to determine the energy scale of cosmic rays bet… ▽ More The accurate determination of the absolute energy scale in cosmic ray measurements is both a challenging and fundamentally important task. We present how measurements of radio pulses from extensive air showers with the Auger Engineering Radio Array, combined with per-event simulations of radio emission using the CoREAS extension of CORSIKA, allow us to determine the energy scale of cosmic rays between $3\cdot 10^{17}$\,eV and several $10^{18}$\,eV. Our analysis accounts for many factors, each of which is controlled on the 5\% level or better. The absolute calibration of the antennas and the entire analog signal chain builds on a Galactic calibration in combination with a detailed understanding of the antenna-gain patterns. Additional key elements include compensation for temperature-dependent signal amplification, continuous detector health monitoring, an active veto for thunderstorm conditions, an unbiased event reconstruction, and per-event atmospheric modeling in the simulations. The analysis benefits from a high-statistics dataset of over 800 measured cosmic ray showers. We describe our analysis method, perform multiple cross-checks, and evaluate systematic uncertainties. We find that absolute energies determined with AERA are 12\% higher than those established with the Auger Fluorescence Detector, a result well in agreement within systematic uncertainties and thus a strong independent confirmation of the absolute energy scale of the Pierre Auger Observatory. △ Less

Submitted 19 September, 2025; v1 submitted 11 July, 2025; originally announced July 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025). 8 pages, 8 figures; v2 with very minor fixes

Report number: PoS-ICRC2025-292

Generative Neural Network for Simulating Radio Emission from Extensive Air Showers

Authors: Pranav Sampathkumar, Tim Huege, Andreas Haungs, Ralph Engel

Abstract: Cosmic ray shower detection using large radio arrays has gained significant traction in recent years. With massive improvements in signal modelling and microscopic simulations, the analysis of incoming events is still severely limited by the simulation cost of radio emission to interpret the data. In this work, we show that a neural network can be used for simulating such radio pulses. We also dem… ▽ More Cosmic ray shower detection using large radio arrays has gained significant traction in recent years. With massive improvements in signal modelling and microscopic simulations, the analysis of incoming events is still severely limited by the simulation cost of radio emission to interpret the data. In this work, we show that a neural network can be used for simulating such radio pulses. We also demonstrate how such a neural network can be used for $X_\mathrm{max}$ reconstruction, while retaining comparable resolution to using full Monte-Carlo CORSIKA/CoREAS simulations for radio emission. △ Less

Submitted 10 July, 2025; originally announced July 2025.

Comments: 39th International Cosmic Ray Conference (ICRC2025) Proceeding

Electric-Field Reconstruction for Radio Detection of Inclined Air Showers in Three Polarizations

Authors: Kewen Zhang, Lukas Gülzow, Tim Huege, Ramesh Koirala, Pengxiong Ma, Matías Tueros, Xin Xu, Chao Zhang, Pengfei Zhang, Yi Zhang

Abstract: Accurate reconstruction of the electric field produced by extensive air showers is essential for the radio-detection technique, as the key parameters of interest of the primary particles that generated the showers are the amplitude, polarization, frequency spectrum, and energy fluence carried by the electric field at each receiving radio antenna. Conventional electric-field reconstruction methods… ▽ More Accurate reconstruction of the electric field produced by extensive air showers is essential for the radio-detection technique, as the key parameters of interest of the primary particles that generated the showers are the amplitude, polarization, frequency spectrum, and energy fluence carried by the electric field at each receiving radio antenna. Conventional electric-field reconstruction methods primarily focus on antennas with two horizontal polarizations. In this work, we introduce an analytic $χ^2$ minimization method that is applicable to both two and three polarizations. This solution has been verified for simple and realistic antenna responses, with a particular focus on inclined air showers. Our method achieves standard deviations better than 4\% and 6\% for the estimation of the Hilbert peak envelope amplitude of the electric field and the energy fluence, respectively, with an antenna-response-dependent bias. Additionally, we have studied the dependence of the method with arrival direction showing that it has a good performance in the zenith range from 63$^\circ$ up to 80$^\circ$. This work also demonstrates that incorporating vertically polarized antennas enhances the precision of the reconstruction, leading to a more accurate and reliable electric-field estimation for inclined air showers. △ Less

Submitted 10 July, 2025; v1 submitted 9 July, 2025; originally announced July 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2023). 10 pages, 4 figures

Report number: PoS(ICRC2025)447

Signal Model and Energy Reconstruction for the Radio Detection of Inclined Air Showers in the 50-200 MHz Frequency Band

Authors: Lukas Gülzow, Ralph Engel, Tim Huege, Markus Roth, Felix Schlüter

Abstract: The radio emission of cosmic-ray air-showers changes significantly depending on parameters like signal frequency, magnetic field configuration and observing altitude. We use CoREAS simulations to adapt an existing signal model for the radio emission of inclined showers in the 30-80 MHz frequency band to the wide 50-200 MHz band. Our model uses a parametrisation of the charge excess fraction to iso… ▽ More The radio emission of cosmic-ray air-showers changes significantly depending on parameters like signal frequency, magnetic field configuration and observing altitude. We use CoREAS simulations to adapt an existing signal model for the radio emission of inclined showers in the 30-80 MHz frequency band to the wide 50-200 MHz band. Our model uses a parametrisation of the charge excess fraction to isolate the geomagnetic emission component. We reconstruct the geomagnetic radiation energy by fitting a lateral distribution function, provided by the model, to the geomagnetic energy fluence distribution of the shower. After we correct for the shower geometry and air density, we correlate the radiation energy with the electromagnetic energy of the shower. We show that the method intrinsic energy resolutions < 5% for the sites of the Pierre Auger Observatory and GRANDProto300. For GRANDProto300, we test the reconstruction with simulations of a realistic, sparse antenna grid and with added noise, and find an energy resolution of < 10% with negligible bias. We do a similar study for a much larger array of 10, 000 km2 with 1 km antenna spacing. We find an intrinsic energy resolution of < 10%. △ Less

Submitted 9 July, 2025; originally announced July 2025.

Comments: Presented at the 39th International Cosmic Ray Conference (ICRC 2025). 9 pages, 5 figures

Report number: PoS(ICRC2025)283

Measuring the muon content of inclined air showers using AERA and the water-Cherenkov detectors of the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, G. A. Anastasi, L. Anchordoqui, B. Andrada, L. Andrade Dourado, S. Andringa, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato , et al. (338 additional authors not shown)

Abstract: We present a novel approach for assessing the muon content of air showers with large zenith angles on a combined analysis of their radio emission and particle footprint. We use the radiation energy reconstructed by the Auger Engineering Radio Array (AERA) as an energy estimator and determine the muon number independently with the water-Cherenkov detector array of the Pierre Auger Observatory, depl… ▽ More We present a novel approach for assessing the muon content of air showers with large zenith angles on a combined analysis of their radio emission and particle footprint. We use the radiation energy reconstructed by the Auger Engineering Radio Array (AERA) as an energy estimator and determine the muon number independently with the water-Cherenkov detector array of the Pierre Auger Observatory, deployed on a 1500 m grid. We focus our analysis on air showers with primary energy above 4 EeV to ensure full detection efficiency. Over approximately ten years of accumulated data, we identify a set of 40 high-quality events that are used in the analysis. The estimated muon contents in data are compatible with those for iron primaries as predicted by current-generation hadronic interaction models. This result can be interpreted as a deficit of muons in simulations as a lighter mass composition has been established from Xmax measurements. This muon deficit was already observed in previous analyses of the Auger Collaboration and is confirmed using hybrid events that include radio measurements for the first time. △ Less

Submitted 7 January, 2026; v1 submitted 3 July, 2025; originally announced July 2025.

Comments: 10 pages, 6 figures

Journal ref: Phys. Rev. D 112, 123042 (2025)

The Energy Spectrum of Ultra-High Energy Cosmic Rays across Declinations $-90^\circ$ to $+44.8^\circ$ as measured at the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, G. A. Anastasi, L. Anchordoqui, B. Andrada, L. Andrade Dourado, S. Andringa, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato , et al. (338 additional authors not shown)

Abstract: The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range $-90^\circ \leqδ\leq +44.8^\circ$ using data from $\sim 310{,}000$ events accrued at the Pierre Auger Observatory from an exposure of $(104{,}900\pm 3{,}100)$ km$^2\,$sr$\,$yr. No significant variations of energy spectra with declination are observed, after allowing or not for non-uniformities across th… ▽ More The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range $-90^\circ \leqδ\leq +44.8^\circ$ using data from $\sim 310{,}000$ events accrued at the Pierre Auger Observatory from an exposure of $(104{,}900\pm 3{,}100)$ km$^2\,$sr$\,$yr. No significant variations of energy spectra with declination are observed, after allowing or not for non-uniformities across the sky arising from the well-established dipolar anisotropies in the arrival directions of ultra-high energy cosmic rays. Additionally, the instep feature in the spectrum at $\simeq$ 10 EeV reported previously is now established at a significance above $5\,σ$. The quasi-uniformity of the energy spectrum across declinations disfavors an origin for the instep from a few distinctive sources. △ Less

Submitted 28 October, 2025; v1 submitted 13 June, 2025; originally announced June 2025.

Comments: 17 pages, 4 figures, version accepted for publication in Physical Review Letters

Journal ref: Phys.Rev.Lett. 135 (2025) 24, 241002

SMIET: Fast and accurate synthesis of radio pulses from extensive air shower using simulated templates

Authors: Mitja Desmet, Keito Watanabe, Tim Huege, Stijn Buitink

Abstract: Interpreting the data from radio detectors for extensive air showers typically relies on Monte-Carlo based simulation codes, which, despite their accuracy are computationally expensive and present bottlenecks for analyses. To address this issue we developed a novel method called template synthesis, which synthesises the radio emission from cosmic ray air showers in seconds. This hybrid approach us… ▽ More Interpreting the data from radio detectors for extensive air showers typically relies on Monte-Carlo based simulation codes, which, despite their accuracy are computationally expensive and present bottlenecks for analyses. To address this issue we developed a novel method called template synthesis, which synthesises the radio emission from cosmic ray air showers in seconds. This hybrid approach uses a microscopically simulated, sliced shower (the origin) as an input. It rescales the emission from each slice individually to synthesise the emission from a shower with different properties (the target). In order to be able to change the arrival direction during synthesis, we adjust the phases based on the expected geometrical delays. We benchmark the method by comparing synthesised traces to CoREAS simulations over a wide frequency range of [30, 500] MHz . The synthesis quality is primarily influenced by the difference in $X_{max}$ between the origin and target shower. When $ΔX_{max} \leq 100 g/cm^2$ , the scatter on the maximum amplitudes of the geomagnetic traces is at most 4%. For the traces from the charge-excess component this scatter is smaller than 6%. We also observe a bias with $ΔX_{max}$ up to 5% for both components, which appears to depend on the antenna position. Since the bias is symmetrical around $ΔX_{max} = 0 g/cm^2$, we can use an interpolation approach to correct for it. We have implemented the template synthesis algorithm in a Python package called \texttt{SMIET}, which includes all the necessary parameters. This package has been successfully tested with air showers with zenith angles up to $50^{\circ}$ and can be used with any atmosphere, observation level and magnetic field. We demonstrate that the synthesis quality remains comparable to our main benchmarks across various scenarios and discuss use cases, including machine-learning-based analyses. △ Less

Submitted 15 May, 2025; originally announced May 2025.

Comments: 38 pages, 15 figures. Submitted to Astroparticle Physics

A LOFAR-style reconstruction of cosmic-ray air showers with SKA-Low

Authors: A. Corstanje, S. Buitink, S. Bouma, M. Desmet, J. R. Hörandel, T. Huege, P. Laub, K. Mulrey, A. Nelles, O. Scholten, K. Terveer, S. Thoudam, K. Watanabe

Abstract: Cosmic-ray air shower detection with the low-frequency part of the Square Kilometre Array (SKA) radio telescope is envisioned to yield very high precision measurements of the particle composition of cosmic rays between $10^{16}$ and $10^{18}$ eV. This is made possible by the extreme antenna density of the core of SKA-Low, surpassing the current most dense radio air shower observatory LOFAR by over… ▽ More Cosmic-ray air shower detection with the low-frequency part of the Square Kilometre Array (SKA) radio telescope is envisioned to yield very high precision measurements of the particle composition of cosmic rays between $10^{16}$ and $10^{18}$ eV. This is made possible by the extreme antenna density of the core of SKA-Low, surpassing the current most dense radio air shower observatory LOFAR by over an order of magnitude. In order to make these measurements, the technical implementation of this observation mode and the development of reconstruction methods have to happen hand-in-hand. As a first lower limit of what is obtainable, we apply the current most precise reconstruction methods as used at LOFAR to a first complete simulation of air shower signals for the SKA-Low array. We describe this simulation setup and discuss the obtainable accuracy and resolution. A special focus is put on effects of the dynamic range of the system, beamforming methods to lower the energy threshold, as well as the limits to the mass composition accuracy given by statistical and systematic uncertainties. △ Less

Submitted 22 June, 2025; v1 submitted 23 April, 2025; originally announced April 2025.

Comments: 14 pages, 10 figures. Accepted for publication in Phys. Rev. D

Ideas and Requirements for the Global Cosmic-Ray Observatory (GCOS)

Authors: Markus Ahlers, Ingo Allekotte, Jaime Alvarez-Muniz, Gioacchino Alex Anastasi, Luis Anchordoqui, Rita de Cassia Dos Anjos, Hari Haran Balakrishnan, Rafael Alves Batista, Jose Bellido, Mario Bertaina, Sonali Bhatnagar, Pierre Billoir, Kathrin Bismark, Teresa Bister, Martina Bohacova, Carla Bonifazi, Fraser Bradfield, Antonella Castellina, Lorenzo Cazon, Kevin Almeida Cheminant, Alan Coleman, Fabio Convenga, Darko Veberič, Paramita Dasgupta, Kai Daumiller , et al. (114 additional authors not shown)

Abstract: After a successful kick-off meeting in 2021. two workshops in 2022 and 2023 on the future Global Cosmic-Ray Observatory (GCOS) focused mainly on a straw man design of the detector and science possibilities for astro- and particle physics. About 100 participants gathered for in-person and hybrid panel discussions. In this report, we summarize these discussions, present a preliminary straw-man desig… ▽ More After a successful kick-off meeting in 2021. two workshops in 2022 and 2023 on the future Global Cosmic-Ray Observatory (GCOS) focused mainly on a straw man design of the detector and science possibilities for astro- and particle physics. About 100 participants gathered for in-person and hybrid panel discussions. In this report, we summarize these discussions, present a preliminary straw-man design for GCOS and collect short write-ups of the flash talks given during the focus sessions. △ Less

Submitted 8 February, 2025; originally announced February 2025.

Comments: 48 pages, 27 figures

A search for the anomalous events detected by ANITA using the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, J. Ammerman Yebra, G. A. Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, L. Apollonio, C. Aramo, P. R. Araújo Ferreira, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato, A. Bartz Mocellin , et al. (352 additional authors not shown)

Abstract: A dedicated search for upward-going air showers at zenith angles exceeding $110^\circ$ and energies $E>0.1$ EeV has been performed using the Fluorescence Detector of the Pierre Auger Observatory. The search is motivated by two "anomalous" radio pulses observed by the ANITA flights I and III which appear inconsistent with the Standard Model of particle physics. Using simulations of both regular cos… ▽ More A dedicated search for upward-going air showers at zenith angles exceeding $110^\circ$ and energies $E>0.1$ EeV has been performed using the Fluorescence Detector of the Pierre Auger Observatory. The search is motivated by two "anomalous" radio pulses observed by the ANITA flights I and III which appear inconsistent with the Standard Model of particle physics. Using simulations of both regular cosmic ray showers and upward-going events, a selection procedure has been defined to separate potential upward-going candidate events and the corresponding exposure has been calculated in the energy range [0.1-33] EeV. One event has been found in the search period between 1 Jan 2004 and 31 Dec 2018, consistent with an expected background of $0.27 \pm 0.12$ events from mis-reconstructed cosmic ray showers. This translates to an upper bound on the integral flux of $(7.2 \pm 0.2) \times 10^{-21}$ cm$^{-2}$ sr$^{-1}$ y$^{-1}$ and $(3.6 \pm 0.2) \times 10^{-20}$ cm$^{-2}$ sr$^{-1}$ y$^{-1}$ for an $E^{-1}$ and $E^{-2}$ spectrum, respectively. An upward-going flux of showers normalized to the ANITA observations is shown to predict over 34 events for an $E^{-3}$ spectrum and over 8.1 events for a conservative $E^{-5}$ spectrum, in strong disagreement with the interpretation of the anomalous events as upward-going showers. △ Less

Submitted 6 February, 2025; originally announced February 2025.

Comments: 10+5 Pages of Manuscript plus Supplemental Material, 3+8 figures, Accepted for publication in Physical Review Letters

Journal ref: Phys. Rev. Lett. 134 (2025) 121003

Search for a diffuse flux of photons with energies above tens of PeV at the Pierre Auger Observatory

Authors: The Pierre Auger Collaboration, A. Abdul Halim, P. Abreu, M. Aglietta, I. Allekotte, K. Almeida Cheminant, A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, G. A. Anastasi, L. Anchordoqui, B. Andrada, L. Andrade Dourado, S. Andringa, L. Apollonio, C. Aramo, E. Arnone, J. C. Arteaga Velázquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato , et al. (337 additional authors not shown)

Abstract: Diffuse photons of energy above 0.1 PeV, produced through the interactions between cosmic rays and either interstellar matter or background radiation fields, are powerful tracers of the distribution of cosmic rays in the Galaxy. Furthermore, the measurement of a diffuse photon flux would be an important probe to test models of super-heavy dark matter decaying into gamma-rays. In this work, we sear… ▽ More Diffuse photons of energy above 0.1 PeV, produced through the interactions between cosmic rays and either interstellar matter or background radiation fields, are powerful tracers of the distribution of cosmic rays in the Galaxy. Furthermore, the measurement of a diffuse photon flux would be an important probe to test models of super-heavy dark matter decaying into gamma-rays. In this work, we search for a diffuse photon flux in the energy range between 50 PeV and 200 PeV using data from the Pierre Auger Observatory. For the first time, we combine the air-shower measurements from a 2 km$^2$ surface array consisting of 19 water-Cherenkov surface detectors, spaced at 433 m, with the muon measurements from an array of buried scintillators placed in the same area. Using 15 months of data, collected while the array was still under construction, we derive upper limits to the integral photon flux ranging from 13.3 to 13.8 km$^{-2}$ sr$^{-1}$ yr$^{-1}$ above tens of PeV. We extend the Pierre Auger Observatory photon search program towards lower energies, covering more than three decades of cosmic-ray energy. This work lays the foundation for future diffuse photon searches: with the data from the next 10 years of operation of the Observatory, this limit is expected to improve by a factor of $\sim$20. △ Less

Submitted 7 November, 2025; v1 submitted 4 February, 2025; originally announced February 2025.

Comments: Published version in JCAP

Journal ref: JCAP 05 (2025) 061

Electric field reconstruction with three polarizations for the radio detection of ultra-high energy particles

Authors: Kewen Zhang, Tim Huege, Ramesh Koirala, Pengxiong Ma, Matías Tueros, Xin Xu, Chao Zhang, Pengfei Zhang, Yi Zhang

Abstract: Accurate reconstruction of the electric field produced by Extensive Air Showers from the signals recorded by the antennas is essential for the radio detection technique, as the key parameters needed to retrieve information about the primary particle that generated the shower are the amplitude, polarization, frequency spectrum and energy fluence carried by the electric field at each measurement pos… ▽ More Accurate reconstruction of the electric field produced by Extensive Air Showers from the signals recorded by the antennas is essential for the radio detection technique, as the key parameters needed to retrieve information about the primary particle that generated the shower are the amplitude, polarization, frequency spectrum and energy fluence carried by the electric field at each measurement position. Conventional electric field reconstruction methods primarily focus on antennas with two horizontal polarizations. In this paper, we introduce an analytical $χ^2$ minimization method that operates with both two and three polarizations, providing the reconstructed electric field at each antenna. This solution has been verified for simple and realistic antenna responses, with a particular focus on inclined air showers. Our method achieves a standard deviation better than 4\% in determining the peak envelope amplitude of the electric field and better than 6\% in the estimation of the energy fluence, with an antenna response dependent bias. Additionally, we have studied the dependence of the method with arrival direction showing that it has a good performance in almost all of them. This work also demonstrates that incorporating vertically polarized antennas enhances the precision of reconstruction, leading to a more accurate and reliable electric field estimation for inclined air showers. Consequently, the method improves our ability to extract information about cosmic rays from the detected signals in current and future experiments. △ Less

Submitted 31 May, 2025; v1 submitted 21 January, 2025; originally announced January 2025.

Aperture correction for Beamforming in radiometric detection of ultra-high energy cosmic rays

Authors: O. Scholten, T. N. G. Trinh, S. Buitink, A. Corstanje, B. M. Hare, T. Huege, B. V. Jhansi, K. Mulrey, A. Nelles, H. Schoorlemmer, S. Thoudam, P. Turekova, K. de Vries

Abstract: For high-energy cosmic-ray physics, it is imperative to determine the mass and energy of the cosmic ray that initiated the air shower in the atmosphere. This information can be extracted from the longitudinal profile of the air shower. In radio-metric observations, this profile is customarily determined through an extensive fitting procedure where calculated radio intensity is fitted to data. Beam… ▽ More For high-energy cosmic-ray physics, it is imperative to determine the mass and energy of the cosmic ray that initiated the air shower in the atmosphere. This information can be extracted from the longitudinal profile of the air shower. In radio-metric observations, this profile is customarily determined through an extensive fitting procedure where calculated radio intensity is fitted to data. Beamforming the measured signals offers a promising alternative to bypass the cumbersome fitting procedure and to determine the longitudinal profile directly. Finite aperture effects in beamforming hamper the resolution with which this profile can be determined. We present a comprehensive investigation of the beamforming resolution in radiometric observations of air showers. There are two, principally different, approaches possible in air-shower beamforming, one where the total beamforming intensity is determined and an alternative where the beamforming trace is cross-correlated with a known response function. The effects due to a finite aperture (size of antenna array and bandwidth) are large for both approaches. We argue that it is possible to correct for the aperture corrections using an unfolding procedure. We give an explicit expression for the folding function, the kernel. Being able to calculate the folding function allows for unfolding the finite aperture effects from the data. We show that, in a model-to-model comparison, this allows for an accurate reconstruction of the current profile as the shower develops in the atmosphere. We present also an example where we reconstruct the longitudinal current profile of a shower developing under thunderstorm conditions where the atmospheric electric fields greatly alter the orientation of the transverse current in the shower front. △ Less

Submitted 19 November, 2024; originally announced November 2024.

Comments: Accepted for publication in Phys. Rev. D

Journal ref: Phys. Rev. D110 (2024) 103036

Broad-band, high-gain, low-frequency Antennas for Radio Detection of Earth-skimming Tau Neutrinos

Authors: Tim Huege, Oliver Krömer

Abstract: A promising approach to detect high-energy tau neutrinos is through the measurement of impulsive radio emission from horizontal air showers initiated in the Earth's atmosphere. Observations at frequencies between 30 and 80 MHz seem particularly promising -- if high-gain antennas focused at the horizon and blocking out as much as possible of the noisy sky are employed. Due to the large wavelengths,… ▽ More A promising approach to detect high-energy tau neutrinos is through the measurement of impulsive radio emission from horizontal air showers initiated in the Earth's atmosphere. Observations at frequencies between 30 and 80 MHz seem particularly promising -- if high-gain antennas focused at the horizon and blocking out as much as possible of the noisy sky are employed. Due to the large wavelengths, however, designing an antenna with the required properties is highly non-trivial at such low frequencies. In this article, we explore suitable antenna designs that provide the desired high gain, possess a smooth beam, are insensitive to ground conditions, are easily impedance-matched over the wide band, and are mechanically simple for deployment in large numbers in inaccessible terrain. In particular, we consider the "rhombus" antenna design for both horizontally and vertically polarized radiation a very attractive option for tau neutrino detection efforts in the atmosphere with the radio technique. △ Less

Submitted 30 October, 2024; originally announced October 2024.

Comments: 15 pages, to be submitted to JINST

Cosmic ray detection with the LOFAR radio telescope

Authors: K. Terveer, S. Bouma, S. Buitink, A. Corstanje, M. Desmet, H. Falcke, B. M. Hare, J. R. Hörandel, T. Huege, N. Karastathis, P. Laub, K. Mulrey, A. Nelles, O. Scholten, P. Turekova, S. Thoudam, G. Trinh, S. ter Veen

Abstract: The LOw Frequency ARray (LOFAR) has successfully measured cosmic rays for over a decade now. With its dense core of antenna fields in the Netherlands, it is an ideal tool for studying the radio emission from extensive air showers in the $10^{16}$ eV to $10^{18.5}$ eV range. Every air shower is measured with a small particle detector array and hundreds of antennas, which sets LOFAR apart from other… ▽ More The LOw Frequency ARray (LOFAR) has successfully measured cosmic rays for over a decade now. With its dense core of antenna fields in the Netherlands, it is an ideal tool for studying the radio emission from extensive air showers in the $10^{16}$ eV to $10^{18.5}$ eV range. Every air shower is measured with a small particle detector array and hundreds of antennas, which sets LOFAR apart from other air shower arrays. We present our current achievements and progress in reconstruction, interpolation, and software development during the final phases of measurement of LOFAR 1.0, before the LOFAR array gets a significant upgrade, including also plans for the final data release and refined analyses. △ Less

Submitted 10 October, 2024; originally announced October 2024.

Comments: Proceedings of the 10th ARENA Workshop 2024

Simulating radio emission from particle cascades with CORSIKA 8

Authors: J. M. Alameddine, J. Albrecht, J. Ammerman-Yebra, L. Arrabito, A. A. Alves Jr., D. Baack, A. Coleman, H. Dembinski, D. Elsässer, R. Engel, A. Faure, A. Ferrari, C. Gaudu, C. Glaser, M. Gottowik, D. Heck, T. Huege, K. H. Kampert, N. Karastathis, L. Nellen, T. Pierog, R. Prechelt, M. Reininghaus, W. Rhode, F. Riehn , et al. (5 additional authors not shown)

Abstract: CORSIKA 8 is a new framework for simulations of particle cascades in air and dense media implemented in modern C++17, based on past experience with existing codes, in particular CORSIKA 7. The flexible and modular structure of the project allows the development of independent modules that can produce a fully customizable particle shower simulation. The radio module in particular is designed to tre… ▽ More CORSIKA 8 is a new framework for simulations of particle cascades in air and dense media implemented in modern C++17, based on past experience with existing codes, in particular CORSIKA 7. The flexible and modular structure of the project allows the development of independent modules that can produce a fully customizable particle shower simulation. The radio module in particular is designed to treat the electric field calculation and its propagation through complex media to each observer location in an autonomous and flexible way. It already allows for the simultaneous simulation of the radio emission calculated with two independent time-domain formalisms, the "Endpoint formalism" as previously implemented in CoREAS and the "ZHS" algorithm as ported from ZHAireS. The design acts as the baseline interface for current and future development for the simulation of radio emission from particle showers in standard and complex scenarios, such as cross-media showers penetrating from air into ice. In this work, we present the design and implementation of the radio module in CORSIKA 8, along with validation studies and a direct comparison of the radio emission from air showers simulated with CORSIKA 8, CORSIKA 7 and ZHAireS. We also present the impact of simulation details such as the step size of simulated particle tracks on radio-emission simulations and perform a direct comparison of the "Endpoints" and "ZHS" formalisms for the same underlying air showers. Finally, we present an in-depth comparison of CORSIKA 8 and CORSIKA 7 for optimum simulation settings and discuss the relevance of observed differences in light of reconstruction efforts for the energy and mass of cosmic rays. △ Less

Submitted 24 September, 2024; originally announced September 2024.

Comments: 17 pages

Journal ref: Astropart. Phys. 166, 103072 (2025)

Electric Field Reconstruction with Information Field Theory

Authors: Simon Strähnz, Tim Huege, Philipp Frank, Torsten Enßlin

Abstract: Reconstructing the electric field from the measured voltages in an antenna, unfolding the antenna response, comes with several problems. Due to the noisiness of the signal it is often necessary to disregard part of the bandwidth of the antenna. It is also not guaranteed, that this system of equations can be inverted at all. In any case, the noise of the measurement will be converted into noise on… ▽ More Reconstructing the electric field from the measured voltages in an antenna, unfolding the antenna response, comes with several problems. Due to the noisiness of the signal it is often necessary to disregard part of the bandwidth of the antenna. It is also not guaranteed, that this system of equations can be inverted at all. In any case, the noise of the measurement will be converted into noise on the electric field. This could be solved by Bayesian inference, however, the electric field is continuous, which would lead to an infinite-dimensional latent space. Information field theory (IFT) has been developed to deal with this problem and allow for Bayesian reasoning on fields. It provides a theoretical backbone and effective tools to approach the inference as a discrete problem in the continuum limit, taking the continuous nature of fields into account. We will present a first working signal model that can be used with IFT-based inference algorithms, which can successfully reconstruct the electric field. The model is based on the current understanding of air shower emission physics, modelling geomagnetic and charge-excess emission and their respective polarisation and spectra separately. Since Bayesian inference provides the posterior distribution, this method also gives an estimate on the uncertainty of the measured field. The performance of this method will be demonstrated with Monte-Carlo simulations of air shower radio signals. △ Less

Submitted 14 October, 2024; v1 submitted 23 September, 2024; originally announced September 2024.

Comments: PoS(ARENA2024)

Template synthesis approach for radio emission from extensive air showers

Authors: Mitja Desmet, Stijn Buitink, David Butler, Tim Huege, Ralph Engel, Olaf Scholten

Abstract: We present a novel way to synthesise the radio emission from extensive air showers. It is a hybrid approach which uses a single microscopic Monte-Carlo simulation to generate the radio emission from a shower with a different longitudinal evolution, primary particle type and energy. The method employs semi-analytical relations which only depend on the shower parameters to transform the radio signal… ▽ More We present a novel way to synthesise the radio emission from extensive air showers. It is a hybrid approach which uses a single microscopic Monte-Carlo simulation to generate the radio emission from a shower with a different longitudinal evolution, primary particle type and energy. The method employs semi-analytical relations which only depend on the shower parameters to transform the radio signal in the simulated antennas. We apply this method to vertical air showers with energies ranging from $10^{17}$ eV to $10^{19}$ eV and compare the results with CoREAS using two different metrics. In order to gauge the performance over our simulation set, we subsequently use every shower in the set as a template to synthesise the emission from the other showers. Depending on the scoring metric, template synthesis reconstructs the radio emission with an accuracy of 5 to 10%. △ Less

Submitted 19 September, 2024; originally announced September 2024.

Comments: Proceedings of the 9th ARENA Workshop 2022

Generalising template synthesis of EAS radio emission to other geometries

Authors: Mitja Desmet, Stijn Buitink, Tim Huege

Abstract: Over the last few decades, radio detection has become one of the standard techniques to study high-energy cosmic-ray air showers. For the purpose of analysing the data, we heavily rely on Monte Carlo simulations. Upcoming dense radio array experiments such as LOFAR2.0 and SKA will, however, reach the limit of what is computationally feasible with these. Other techniques are available, based on mac… ▽ More Over the last few decades, radio detection has become one of the standard techniques to study high-energy cosmic-ray air showers. For the purpose of analysing the data, we heavily rely on Monte Carlo simulations. Upcoming dense radio array experiments such as LOFAR2.0 and SKA will, however, reach the limit of what is computationally feasible with these. Other techniques are available, based on macroscopic quantities, but their accuracy has thus far not been adequate to use them in precision analyses. In this contribution we present the latest update on the template synthesis approach, a hybrid model using both micro- and macroscopic inputs to synthesise the radio emission for an air shower with an arbitrary longitudinal profile. The method starts from the emission of a given shower and employs semi-analytical relations which only depend on the atmospheric depth at shower maximum and antenna position in order to transform it. Core to the template synthesis approach is the slicing of the atmosphere. By considering the radio emission from each slice separately, we only need to explicitly account for shower age effects. In previous work it was shown this could be done over a wide range of primary energy and across primary types for vertical air showers, with an accuracy of 10%. Here, we generalise the method to other zenith angles. We investigate the potential to synthesise between different geometries using a data set consisting of several hundreds of CORSIKA showers with primary energies ranging from $10^{17}$ eV to $10^{19}$ eV. △ Less

Submitted 19 September, 2024; originally announced September 2024.

Comments: Proceedings of the 38th International Cosmic Ray Conference (ICRC2023)

Applying template synthesis to the radio emission from air showers with generic geometries

Authors: Mitja Desmet, Stijn Buitink, Tim Huege

Abstract: Studying high-energy cosmic-ray air showers through the radio emission produced by their secondary particles is a well-established technique. However, due to the increasing size and density of the radio arrays, analyses are running into computational limits, as these rely on Monte Carlo simulations to model the emission. To address this, we have been developing template synthesis. With this method… ▽ More Studying high-energy cosmic-ray air showers through the radio emission produced by their secondary particles is a well-established technique. However, due to the increasing size and density of the radio arrays, analyses are running into computational limits, as these rely on Monte Carlo simulations to model the emission. To address this, we have been developing template synthesis. With this method, we use semi-analytical expressions to describe how the radio emission from an air shower depends on the shower age and the position of the antenna with respect to the shower. These expressions are extracted from a set of microscopic simulations, thus benefiting from their accuracy. Once obtained, we can use these relations to synthesise the emission from an air shower with any longitudinal profile, by using a single Monte Carlo simulation as an input. Previously we have demonstrated that this hybrid approach can synthesise the radio emission from air showers and agrees with results from microscopic simulations within 10%. The method was however limited to a specific geometry. Here we present our first step towards generalising template synthesis across geometries. We found a set of scaling relations which correct for the shower geometry as well as the viewing angle under which the radiation is observed. This allows us to reformulate the semi-analytical relations in a way that does not longer depend on the geometry, significantly reducing the number of parameters that need to be fitted. We apply these scaling relations to a simulation library of CORSIKA showers with a zenith angle of 50 degrees. We then extract the semi-analytical expressions required for template synthesis, and use them to synthesise the emission from air showers with lower zenith angles. We investigate the accuracy by comparing both to microscopic simulations as well as the single geometry version of template synthesis. △ Less

Submitted 19 September, 2024; originally announced September 2024.

Comments: Proceedings of the 10th ARENA Workshop 2024

Validation of straight-line signal propagation for radio signal of very inclined cosmic ray air showers

Authors: Dieder Van den Broeck, Uzair Abdul Latif, Stijn Buitink, Krijn de Vries, Tim Huege

Abstract: An ongoing challenge for radio-based detectors of high-energy cosmic particles is the accurate description of radio signal propagation in natural nonuniform media. For radio signals originating from extensive air showers, the current state of the art simulations often implicitly assume straight-line signal propagation. The refraction due to a nonuniform atmosphere is however expected to have an ef… ▽ More An ongoing challenge for radio-based detectors of high-energy cosmic particles is the accurate description of radio signal propagation in natural nonuniform media. For radio signals originating from extensive air showers, the current state of the art simulations often implicitly assume straight-line signal propagation. The refraction due to a nonuniform atmosphere is however expected to have an effect on the received signal and associated reconstruction. This effect is currently not completely understood for the most inclined geometries. Here, we present a study regarding the validity of straight-line signal propagation when simulating radio emission associated with very inclined air shower geometries. To this end, the calculation of the electric field based on the end point formalism used in CoREAS was improved by use of tabulated ray tracing data. We find a difference of 2% in radiation energy and a difference of O(0.01°) on direction reconstruction when working at frequencies below 600 MHz. We thus find that, for frequencies up to 600 MHz and zenith angles up to 88°, the current straight-line based simulation approaches are accurate. △ Less

Submitted 7 April, 2025; v1 submitted 10 September, 2024; originally announced September 2024.