REVIEW 4 major objections 4 minor 14 references
Giant Atmospheric Showers Detected by the Yakutsk Extensive Air Shower Array
T0 review · 4 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash
Pith's one-line read Over 50 years of Yakutsk operation, the two most powerful air showers on record show about 1.25 times more muons at 600 meters than the QGSJet-II.04 model predicts even for iron primaries, implying an anomalous muon content in…
desk verdict Real data, shaky normalization: the Arian event's muon fraction exceeds unity, so the claimed excess is not yet credible. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the ratio of two lateral distribution functions (LDFs): the all-particle surface-detector density $S(r,\theta)$, normalized at 600 m to $S_{600}(\theta)$, and the underground muon density $S_\mu(r,\theta)$, normalized to $S_{\mu,600}(\theta)$, with muon threshold energy $E_\mu = 1.0 \times \cos\theta$ GeV. The paper's observable is $S_{\mu,600}/S_{600}$, the muon fraction at 600 m from the shower axis. QGSJet-II.04 model simulations supply the reference $S_{\mu,600}$ values for proton and iron primaries at the same energy and zenith angle; because the measured ratio sits about 1.25 times above the iron prediction, the machinery localizes the discrepancy to muon production in the shower cascade.
What would settle it
Measure the energy of a similar giant shower with a method independent of the surface-detector calibration, then compare its $S_{\mu,600}/S_{600}$ ratio with the QGSJet-II.04 iron prediction; a ratio near 0.82 would refute the claimed excess, while a ratio near 1 would confirm it.
Extended reading notes
Core claim
The discovery claim is that the two giant events—Arian from 07/05/1989 and the shower from 02/04/2024—have muon fractions $S_{\mu,600}/S_{600}$ of $10^{1.81-1.74}=1.17$ and $10^{1.48-1.58}=0.8$ at $r=600$ m, averaging approximately 1. The same ratio predicted by QGSJet-II.04 for iron primaries at the same energies and zenith angles is $10^{1.66-1.74}=0.83$ and $10^{1.37-1.58}=0.62$, averaging approximately 0.82. The measured muon content is therefore higher than the most muon-rich standard primary by a factor of about 1.25, which the paper interprets as beyond current model predictions and possibly a sign of exotic primary particles.
Load-bearing premise
The anomaly lives in the comparison between measured muon densities and QGSJet-II.04 predictions, so if the energy assigned to these showers is wrong or the hadronic model is not representative, the muon excess could shrink or disappear.
Editorial extensions
If this is right
- Muon production in extreme-energy air showers is underestimated by a factor of about 1.25 even when the primary is assumed to be iron, so current hadronic interaction models need additional muon-production channels or modified shower development.
- The consistency of the muon fraction between the two events, registered decades apart with different detector configurations, argues that the excess is a systematic feature of the highest-energy showers rather than a single measurement artifact.
- If standard nuclei cannot account for the muon content, exotic primary particles become a plausible explanation, as the authors state.
- At 600 m from the axis, the surface detectors in these events appear to be recording essentially the same muon population as the underground detectors, so all-particle signals at that distance are muon-dominated.
- A third giant event with an independent energy measurement would settle whether the anomaly is real or tied to the Yakutsk energy calibration.
Reading between the lines
- A test the paper does not run: compute the ratio using only relative detector responses rather than absolute energies, which would separate a genuine muon anomaly from an energy-scale error.
- If the muon excess is physical, hybrid observatories with an independent energy scale should see the muon fraction rise toward the highest energies in their own event samples before another $10^{20}$ eV shower is captured.
- The authors' plan to search lower energies implies a sharp prediction: the excess should appear gradually with energy if it comes from hadronic physics, and its absence at lower energies would complicate the exotic-primary explanation.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports two ultra-high-energy extensive air showers detected at the Yakutsk array, with energies near 10^20 eV, and presents their lateral distributions of charged particles and muons. The central claim is that the muon fraction at 600 m, S_mu,600/S600, is abnormally high (about 1 on average) compared with QGSJet-II.04 predictions for proton and iron primaries (about 0.82 for iron), which the authors interpret as evidence of a breakdown of hadronic interaction models or of exotic primary particles. The paper gives the fitted parameters in Table 1, LDF plots in Figs. 2 and 4, and raw muon-counter readings for the 2024 event in Table 2.
Significance. If substantiated, the claimed muon excess would have strong implications for ultra-high-energy hadronic interactions and cosmic-ray composition. The paper is valuable for reporting two exceptionally rare giant events with full detector footprints and raw muon readings. However, the central claim rests on only two selected events, a single hadronic model, and a model-dependent energy scale. More importantly, the paper's own numbers for the Arian event imply S_mu,600/S600 > 1, which is unphysical if both quantities are in the same units; this internal inconsistency is not acknowledged. The manuscript is transparent about the data but lacks the cross-calibration and systematic-error treatment needed to support its conclusion.
major comments (4)
- [Table 1 and Discussion] The Arian event's quoted values, log S600(θ) = 1.74 ± 0.02 and log S_mu,600(θ) = 1.81 ± 0.04, give S_mu,600/S600 = 10^{0.07} = 1.17. Since S600 is the total charged-particle density and S_mu,600 is the muon density at the same 600 m distance, a ratio exceeding unity has no physical interpretation if both quantities have the same units. This indicates a relative normalization offset between the surface and underground muon detector systems. The paper's statement that both detectors 'registered virtually the same particles' papers over this inconsistency. The authors must provide a cross-calibration of the two detector responses and re-evaluate the muon excess after correcting any normalization offset; without this, the central claim is unsupported.
- [Sections 'Event from 07/05/1989' and 'Event from 02/04/2024'] The primary energies are inferred from S600 using a calibration (reference [13]) based on the same class of hadronic models, QGSJet-II.04, that is then used to compute the expected muon densities. This creates a circularity: the muon excess is measured relative to predictions of the very model class that sets the energy scale. The paper does not quantify the systematic uncertainty in the energy scale, the muon-density predictions, or the detector calibrations. The authors should show how the ratio S_mu,600/S600 changes under e.g. a ±20% variation of the energy scale and under different hadronic models, and demonstrate that the claimed excess survives.
- [Discussion and Conclusion] The 'average' muon fraction is based on only two events, selected a posteriori because they were the most powerful and triggered all detectors. No selection criteria or trials factor is given. With two events, the statistical significance of a 1.25-fold enhancement over the iron prediction is not established. The authors should report the statistical uncertainty on the average ratio and discuss the probability of observing such a deviation from expectations given the selection procedure.
- [Figs. 2 and 4] The model predictions are shown only for QGSJet-II.04. The conclusion 'beyond current model predictions' requires comparison with other contemporary hadronic models such as EPOS-LHC and Sibyll 2.3d, which differ in muon production. Without such a comparison, the claim that the muon excess is beyond all current models is not robust.
minor comments (4)
- [Table 1] The column headers 'LG' and 'BG' are not defined in the text; they should be specified in the caption or a note.
- [Fig. 2 caption] The caption contains a Cyrillic 'и' ('protons with energy 1020 eV и θ = 59°') that should be replaced with 'and'.
- [Section 'Event from 07/05/1989'] The notation log10[S_mu,600^exp(E,59°)] = 1.81 ± 0.04 is confusing because the energy E is not defined in that expression; it would be clearer to state the ratio explicitly in the text.
- [Throughout] The threshold energy for muon detectors is stated inconsistently: Table 1 uses E_mu = 1.0 × cosθ GeV, while the text mentions E_mu ≥ 1.92 GeV and E_mu ≥ 1.83 GeV; these should be defined consistently.
Circularity Check
No significant circularity: the muon excess is a direct comparison of measured muon densities with external QGSJet-II.04 simulations; no fitted parameter is renamed as a prediction.
full rationale
The paper's central claim is that two giant showers have abnormally high muon content. The experimental quantities log S_mu,600 = 1.81 ± 0.04 and 1.48 ± 0.02 are obtained by fitting approximation (2) to underground muon detector readings (Table 1, Figs. 2 and 4). The QGSJet-II.04 values (1.51, 1.66, 1.30, 1.37) are explicitly introduced as model simulations ('Corresponding muon densities were calculated with the use of QGSjet-II.04 model'), not as fits to the same data. The SD LDF comparison to the model is a consistency check, and the energy estimates are quoted from prior publications (including [13]); even if that energy scale is model-dependent, the muon densities themselves are independently measured and are not defined in terms of the model. The unphysical Arian ratio S_mu,600/S600 = 1.17 indicates a possible detector-normalization inconsistency, but that is a calibration/correctness issue rather than a circular derivation. No equation in the paper defines a predicted quantity in terms of the measured quantity, and no load-bearing argument reduces to a self-citation. Hence no significant circularity is found.
Assumptions & free parameters
free parameters (6)
- S600 for Arian event =
10^1.74 m^-2 (log10)
- S600 for 2024 event =
10^1.58 m^-2 (log10)
- beta(theta) for each event =
not reported numerically
- S_mu,600 for Arian event =
10^1.81 m^-2 (log10)
- S_mu,600 for 2024 event =
10^1.48 m^-2 (log10)
- Primary energy estimates =
10^20.05 eV and 10^19.81 eV
assumptions (4)
- domain assumption QGSJet-II.04 accurately predicts muon production in ultra-high-energy air showers.
- domain assumption The Yakutsk energy reconstruction from S600 is valid at energies near 10^20 eV.
- domain assumption The lateral distribution functions in Eqs. (1) and (2) adequately describe the measured showers.
- domain assumption Comparing only proton and iron primaries covers the plausible standard composition range.
invented entities (1)
-
Unspecified exotic primary particles
Cite this review
Pith. "Pith review of Giant Atmospheric Showers Detected by the Yakutsk Extensive Air Shower Array." pith.science (2026). https://pith.science/paper/LDGBMGWA
@misc{pith2026250600517,
author = {Pith},
title = {Pith review of: Giant Atmospheric Showers Detected by the Yakutsk Extensive Air Shower Array},
year = {2026},
howpublished = {\url{https://pith.science/paper/LDGBMGWA}},
note = {Machine review of arXiv:2506.00517}
}
abstract
The two most powerful extensive air showers (EAS) with energies of about $10^{20}$ eV, registered at the Yakutsk EAS array during the entire observation period of 1974-2024, are considered. Both showers hit the array near the center and triggered all surface detectors and underground muon detectors with a threshold energy of $E_{\mu} = 1.0 \times \cos \theta$ GeV. These events have an abnormally high fraction of muons, which is beyond current model predictions. This may change our understanding of hadron interactions at ultra-high energy, but there is also a possibility that these showers were initiated by some exotic primary particles.
Reference graph
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Reviewed August 7, 2026 · model on record in the stance chip above.
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