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arxiv: 2606.28068 · v1 · pith:FUNL7QLRnew · submitted 2026-06-26 · 🌌 astro-ph.HE · astro-ph.IM

Measuring High-Energy Cosmic Particles with the SKA

Tim Huege , Katharine Mulrey , Sjoerd Bouma , Justin Bray , Stijn Buitink , Arthur Corstanje , Vital De Henau , Edwin Dickinson
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Brian Hare Haoning He J\"org H\"orandel Clancy James Philipp Laub Xingyu Li Marten Lourens Hermann-Josef Mathes Anna Nelles Subhadip Saha Felix Schl\"uter Olaf Scholten Ralph Spencer Christopher Sterpka Karen Terveer Satyendra Thoudam Gia Trinh Paulina Turekova Darko Veberic Keito Watanabe Chao Zhang Pengfei Zhang Yi Zhang
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Pith reviewed 2026-06-29 02:45 UTC · model grok-4.3

classification 🌌 astro-ph.HE astro-ph.IM
keywords cosmic raysair showersSKA-Lowradio detectionshower maximumPeV-EeV energieshadronic interactionsgamma-ray separation
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The pith

SKA-Low will reconstruct the depth of cosmic-ray air showers to better than 8 g/cm² using its dense core and broad bandwidth.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper claims that SKA-Low can measure air showers from cosmic rays in the PeV to EeV range with detail unmatched by current or planned instruments. This precision targets the depth of shower maximum, a key mass-sensitive observable, at a resolution better than 8 g/cm². The measurements would cover the transition between Galactic and extragalactic cosmic-ray sources and open new channels for studying hadronic interactions and possible PeV gamma rays. A dedicated particle detector array enables these observations to run alongside regular telescope operations. The combination is presented as a way to investigate cosmic-ray origins through radio detection of individual showers.

Core claim

SKA-Low's densely instrumented core and broad bandwidth enable measurements of individual air showers with unmatched detail, including depth of shower maximum reconstruction to better than 8 g/cm², full shower reconstruction down to PeV energies, photon-hadron separation, and studies of anomalous showers from high-energy hadronic interactions.

What carries the argument

SKA-Low's densely instrumented core and broad bandwidth for radio detection of air showers.

If this is right

  • Composition measurements become possible across the Galactic-to-extragalactic transition region.
  • New interferometric techniques allow full air-shower reconstruction over a wide energy range.
  • Anomalous air showers provide a channel to study high-energy hadronic interactions.
  • PeV gamma-ray air showers from Galactic sources may be detectable via photon-hadron separation.
  • Lightning imaging becomes feasible as a related application.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the resolution holds, SKA-Low data could directly test models of cosmic-ray acceleration sites by linking shower mass to arrival direction and energy spectra.
  • The commensal operation with regular observations implies that cosmic-ray science requires no dedicated telescope time beyond the particle array trigger.
  • Success at PeV energies would create overlap with ground-based gamma-ray telescopes, allowing cross-checks on hadronic versus electromagnetic shower discrimination.

Load-bearing premise

SKA-Low will reach its design sensitivity, bandwidth, and calibration accuracy, and the reconstruction methods will deliver the stated resolution on real data rather than only in simulations.

What would settle it

Actual observations with the completed SKA-Low showing a depth of shower maximum resolution no better than existing detectors would falsify the central performance claim.

Figures

Figures reproduced from arXiv: 2606.28068 by Anna Nelles, Arthur Corstanje, Brian Hare, Chao Zhang, Christopher Sterpka, Clancy James, Darko Veberic, Edwin Dickinson, Felix Schl\"uter, Gia Trinh, Haoning He, Hermann-Josef Mathes, J\"org H\"orandel, Justin Bray, Karen Terveer, Katharine Mulrey, Keito Watanabe, Marten Lourens, Olaf Scholten, Paulina Turekova, Pengfei Zhang, Philipp Laub, Ralph Spencer, Satyendra Thoudam, Sjoerd Bouma, Stijn Buitink, Subhadip Saha, Tim Huege, Vital De Henau, Xingyu Li, Yi Zhang.

Figure 1
Figure 1. Figure 1: The cosmic-ray energy spectrum, adapted from Evoli (2018). Also shown are the gamma-ray and neutrino fluxes, together with the LHC center-of-mass energy. The arrow indicates the energy range accessible to the SKA. higher energies, around 3 × 1018 eV, the spectrum flattens again in the so-called ankle. This feature is widely interpreted as the point where extragalactic sources begin to dominate the flux, ov… view at source ↗
Figure 2
Figure 2. Figure 2: Left: The radio-emission footprint of a typical air shower, filtered to a frequency band of 30 − 350 MHz, indicative of the SKA-Low frequency band of 50 − 350 MHz. Right: Simulated radio pulse for a position inside the Cherenkov cone in the time domain (top) and frequency domain (bottom). Figure adapted from Corstanje et al. (2023). densest array with which air-showers have been measured so far, antenna de… view at source ↗
Figure 3
Figure 3. Figure 3: Left: Potential layout of the triggering particle detector array for cosmic ray detection. Right: Radio-emission footprint as it would be measured with SKA-Low. Figure adapted from Corstanje et al. (2025). the SKA-Low system. This observing mode will allow fully commensal observations of air showers during “regular” astronomical observations, which is a necessary requirement as cosmic-ray studies require t… view at source ↗
Figure 4
Figure 4. Figure 4: Schematic of cosmic-ray observations at SKA-Low. The red box indicates dedicated electronics to form a cosmic-ray trigger. An external cosmic-ray trigger will be generated by installing a particle detector array at the SKA￾Low site. As described in the previous section, cosmic-ray air showers produce a particle front that reaches the ground at the same time as the radio signal. The signal from the particle… view at source ↗
read the original 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 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript presents a science case for cosmic-ray air-shower observations with SKA-Low in the PeV–EeV range. It claims that the telescope’s dense core and bandwidth will enable unmatched detail on individual showers, including Xmax reconstruction to better than 8 g/cm², full shower reconstruction down to PeV energies, efficient photon/hadron separation, and studies of hadronic interactions via anomalous showers. The text outlines the observational strategy, signal properties, detector design, and summarizes accompanying book chapters on composition, interferometric methods, and related topics.

Significance. If the stated performance is achieved, the work would open a distinctive window on the Galactic-to-extragalactic transition with mass-sensitive observables at a precision not available to existing or planned arrays, while also providing new channels for hadronic-interaction tests and PeV gamma-ray searches.

major comments (2)
  1. [Abstract] Abstract: The headline claim that Xmax will be reconstructed with resolution better than 8 g/cm² is presented without any derivation, simulation results, error budget, or reference to the specific reconstruction algorithm or calibration requirements inside this manuscript. Because this number is load-bearing for the central assertion of “unmatched” precision, its basis must be supplied or explicitly cited.
  2. [Abstract] Abstract and § on detector design: The statements that “new reconstruction methods are expected to enable full air shower reconstruction across a wide energy range, down to PeV levels” and that “efficient photon/hadron separation may offer an opportunity” rest on design specifications and untested assumptions about real-data performance; no propagation of RFI, calibration, or bandwidth uncertainties is shown to support these expectations.
minor comments (1)
  1. [Abstract] The manuscript repeatedly uses future-tense phrasing (“will be able,” “will allow”) for performance claims; a short paragraph distinguishing design goals from demonstrated simulation results would improve clarity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments, which help clarify the presentation of our science case. This manuscript is an overview that summarizes results from accompanying book chapters; we address the points below by adding explicit references and clarifications.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The headline claim that Xmax will be reconstructed with resolution better than 8 g/cm² is presented without any derivation, simulation results, error budget, or reference to the specific reconstruction algorithm or calibration requirements inside this manuscript. Because this number is load-bearing for the central assertion of “unmatched” precision, its basis must be supplied or explicitly cited.

    Authors: We agree the basis must be supplied. The <8 g/cm² Xmax resolution is obtained from detailed Monte Carlo simulations and interferometric reconstruction algorithms described in the accompanying book chapters on composition measurements and next-generation interferometric reconstruction techniques. We will revise the abstract and introduction to include explicit citations to those chapters together with a short statement of the simulation framework and assumed calibration precision. revision: yes

  2. Referee: [Abstract] Abstract and § on detector design: The statements that “new reconstruction methods are expected to enable full air shower reconstruction across a wide energy range, down to PeV levels” and that “efficient photon/hadron separation may offer an opportunity” rest on design specifications and untested assumptions about real-data performance; no propagation of RFI, calibration, or bandwidth uncertainties is shown to support these expectations.

    Authors: These statements are prospective and rest on SKA-Low design specifications and preliminary simulations presented in the chapters on interferometric methods and PeV gamma-ray prospects. A complete propagation of RFI, calibration and bandwidth uncertainties is ongoing work and lies outside the scope of this overview paper. We will add a clarifying sentence noting the assumptions and directing readers to the detailed chapters for the underlying simulation studies. revision: partial

Circularity Check

0 steps flagged

No circularity: forward-looking science case with no derivations or self-referential fits

full rationale

The manuscript is a prospective science case paper. It states expected performance figures (e.g., Xmax resolution <8 g/cm²) as design goals based on SKA-Low specifications and external reconstruction techniques, without presenting equations, parameter fits, or derivations that could reduce to the paper's own inputs. No load-bearing steps invoke self-citations as uniqueness theorems or rename fitted quantities as predictions. The text is self-contained against external benchmarks and contains no internal derivation chain to inspect.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The central projections rest on the unverified assumption that SKA-Low will meet its design specifications and that existing radio-reconstruction techniques will scale as simulated. No free parameters or new entities are introduced in the abstract.

axioms (1)
  • domain assumption SKA-Low will achieve its specified sensitivity, bandwidth, and calibration performance in the relevant frequency range.
    All resolution and reconstruction claims depend on this instrument-level premise.

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Reference graph

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