arxiv: 2605.00232 · v1 · submitted 2026-04-30 · ✦ hep-ex · hep-ph

Recognition: unknown

Cosmic Ray Physics with the KM3NeT Telescopes

Br\'ian \'O Fearraigh (on behalf of the KM3NeT Collaboration)

Authors on Pith no claims yet

Pith reviewed 2026-05-09 19:35 UTC · model grok-4.3

classification ✦ hep-ex hep-ph

keywords KM3NeTatmospheric muonsMuon PuzzleDaemonfluxcosmic ray physicsneutrino telescopesCherenkov detection

0 comments

The pith

KM3NeT telescopes use Daemonflux model to match atmospheric muon data to simulations.

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

The KM3NeT/ARCA and KM3NeT/ORCA detectors measure atmospheric muons penetrating the Mediterranean Sea at different depths, providing wide energy coverage. Incorporating the Daemonflux atmospheric lepton model into the Monte Carlo simulations has resolved the previous discrepancy with observed muon data, addressing the Muon Puzzle common in cosmic ray experiments. This allows for a comprehensive description of the atmospheric muon flux. The muons are also used to calibrate the detectors and constrain uncertainties in seawater optical properties. An early measurement of the atmospheric muon neutrino flux from ORCA data is included.

Core claim

Incorporation of the recent atmospheric lepton model Daemonflux into the KM3NeT Monte Carlo event generator for atmospheric muon bundles has resulted in a stark alleviation of the atmospheric muon data-Monte Carlo simulation discrepancy and a comprehensive description of the atmospheric muon data in KM3NeT.

What carries the argument

The Daemonflux model for atmospheric lepton production and propagation, integrated into simulations of muon bundles detected via Cherenkov radiation in seawater.

If this is right

Atmospheric muons enable calibration of the KM3NeT detectors.
Systematic uncertainties related to the optical properties of the instrumented seawater can be constrained.
The combined ARCA and ORCA setups cover a broad energy range for cosmic ray physics studies.
The atmospheric muon neutrino flux can be measured with increasing precision as more detection units are deployed.

Where Pith is reading between the lines

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

If the Daemonflux model holds, other cosmic ray and neutrino experiments may adopt it to reduce similar background discrepancies.
Improved muon modeling could enhance the sensitivity of KM3NeT to astrophysical neutrinos by better subtracting atmospheric backgrounds.
Full deployment of KM3NeT could provide tests of the model at energies beyond current reach.

Load-bearing premise

The Daemonflux model accurately describes atmospheric lepton production and propagation independently of KM3NeT-specific detector effects.

What would settle it

A significant mismatch between KM3NeT atmospheric muon data and Daemonflux-based Monte Carlo predictions in a high-statistics energy bin would falsify the claim of comprehensive description.

read the original abstract

The KM3NeT research infrastructure instruments a large volume of seawater using photomultiplier tubes, which are sensitive to the Cherenkov radiation stimulated by the products of neutrino interactions in the water, as well as that stimulated by atmospheric muons which penetrate the sea depths. The KM3NeT/ARCA and KM3NeT/ORCA detectors are situated at different depths in the Mediterranean Sea, with different extension and densities of the photo-detection elements. Although operating independently, taken as a whole the two detectors provide a wide energy coverage for the atmospheric muons flux. Through the detection and analysis of these atmospheric muons, a variety of physics studies are possible with the KM3NeT telescope. A measurement of the atmospheric muon neutrino flux has been carried out with data from the initial six detection units of the KM3NeT/ORCA detector. Relatedly to the atmospheric muon flux, the recent atmospheric lepton model `Daemonflux' has been incorporated into the KM3NeT Monte Carlo event generator for atmospheric muon bundles. This has resulted in a stark alleviation of the atmospheric muon data-Monte Carlo simulation discrepancy - a systemic issue in cosmic ray experiments referred to as the `Muon Puzzle' - and a comprehensive description of the atmospheric muon data in KM3NeT. These atmospheric muons are also used in the calibration of the detectors, as well as constraining systematic uncertainties in the detectors such as the optical properties of the instrumented seawater. An overview of these topics, and other cosmic ray analyses, is presented.

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.

Desk Editor's Note private letter to a colleague

KM3NeT's early ORCA muon measurement and Daemonflux update address the Muon Puzzle in a useful but still qualitative way.

read the letter

Hi, this paper is an overview of cosmic-ray work at KM3NeT, built around atmospheric muons seen in their seawater arrays. The concrete new pieces are a flux measurement using the first six ORCA units and the report that swapping in the Daemonflux atmospheric-lepton model largely removes the long-standing data-Monte Carlo mismatch for muon bundles. That mismatch is the so-called Muon Puzzle, and the abstract presents the improvement as a clear win for background modeling in neutrino astronomy. The authors also note that the same muons are already being used for detector calibration and for constraining water optical properties, which is standard but still worth documenting for a new instrument. The wide depth coverage between ARCA and ORCA is a practical advantage they highlight correctly. The main limitation is that the abstract gives no numbers: no multiplicity spectra, no depth-intensity curves, no before-and-after chi-squared or pull values, and no statement on whether Daemonflux parameters were taken exactly as published or adjusted to fit KM3NeT data. Without those details the claim of “stark alleviation” and “comprehensive description” stays hard to weigh. If the full text shows the model was used unchanged and still matches, the result is more convincing; if any tuning occurred, the circularity concern in the stress-test note is real. The paper does not appear to invent new physics or over-claim, just reports what the collaboration has done so far. It is aimed at people already following underwater neutrino telescopes or the cosmic-ray muon problem. A reader who wants a status update on KM3NeT muon analyses will find it helpful, but it is incremental rather than field-redefining. I would send it to peer review because it contains real data from a major experiment and engages an open systematic issue; reviewers can ask for the missing quantitative comparisons and a clearer statement on parameter handling.

Referee Report

2 major / 1 minor

Summary. The manuscript provides an overview of cosmic ray physics with the KM3NeT/ARCA and KM3NeT/ORCA detectors. It reports a measurement of the atmospheric muon neutrino flux using initial data from six ORCA detection units, the incorporation of the Daemonflux atmospheric lepton model into the Monte Carlo simulation for atmospheric muon bundles, which is stated to have produced a stark alleviation of the data-MC discrepancy known as the Muon Puzzle along with a comprehensive description of the atmospheric muon data, and the use of these muons for detector calibration and constraining systematics including seawater optical properties. The differing depths and densities of the two detectors are noted to enable wide energy coverage for the atmospheric muon flux.

Significance. If the claimed improvement in atmospheric muon data-MC agreement is supported by quantitative evidence, the work would contribute to addressing the Muon Puzzle in cosmic ray physics by validating an external lepton production model and demonstrating KM3NeT's utility for such studies. The complementary detector configurations for broad energy coverage and the practical application to calibration and systematics are positive aspects.

major comments (2)

Abstract: the assertion of 'stark alleviation' of the Muon Puzzle and 'comprehensive description' of the atmospheric muon data following Daemonflux incorporation is presented without any quantitative metrics (e.g., chi-squared values, discrepancy reduction factors, or before/after comparisons), error bars, or references to specific figures or tables showing muon-bundle multiplicity or depth-intensity distributions. This absence prevents evaluation of the strength of the central claim.
Section describing Daemonflux incorporation into the Monte Carlo: it is not stated whether the model parameters were taken unchanged from the original Daemonflux publication or adjusted to match KM3NeT data. Without this information, it is impossible to determine if the reported agreement constitutes an independent test or involves post-hoc tuning.

minor comments (1)

Abstract: the specific energy ranges covered by ARCA versus ORCA and the exact number of photo-detection elements could be stated more precisely to support the claim of wide energy coverage.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thorough review and constructive comments on our manuscript. We address each major comment below and describe the revisions that will be made to strengthen the presentation.

read point-by-point responses

Referee: Abstract: the assertion of 'stark alleviation' of the Muon Puzzle and 'comprehensive description' of the atmospheric muon data following Daemonflux incorporation is presented without any quantitative metrics (e.g., chi-squared values, discrepancy reduction factors, or before/after comparisons), error bars, or references to specific figures or tables showing muon-bundle multiplicity or depth-intensity distributions. This absence prevents evaluation of the strength of the central claim.

Authors: We agree that the abstract would benefit from explicit quantitative support and figure references to allow readers to assess the improvement immediately. The body of the manuscript presents the data-MC comparisons for muon-bundle multiplicity and depth-intensity distributions that demonstrate the alleviation of the discrepancy. We will revise the abstract to include a concise quantitative statement on the improvement (e.g., reduction in discrepancy) together with references to the relevant figures and tables. We will also verify that chi-squared or equivalent metrics are clearly reported in the main text section on the atmospheric muon results. revision: yes
Referee: Section describing Daemonflux incorporation into the Monte Carlo: it is not stated whether the model parameters were taken unchanged from the original Daemonflux publication or adjusted to match KM3NeT data. Without this information, it is impossible to determine if the reported agreement constitutes an independent test or involves post-hoc tuning.

Authors: We appreciate this clarification request. The Daemonflux model parameters were taken directly from the original publication without any adjustment or tuning to the KM3NeT data. The observed improvement therefore represents an independent test of the model. We will add an explicit statement to this effect in the Monte Carlo simulation section to eliminate ambiguity. revision: yes

Circularity Check

0 steps flagged

No circularity: external model incorporated as independent input

full rationale

The paper describes incorporating the external Daemonflux atmospheric lepton model into the KM3NeT Monte Carlo generator, which then produces better agreement with observed atmospheric muon data. No derivation chain, equations, or parameter fitting is presented in the abstract or described steps that would reduce the reported alleviation to a self-fit or self-citation. The central claim treats Daemonflux as an a priori input whose use resolves the Muon Puzzle discrepancy, with no evidence of post-hoc tuning or renaming of results as predictions. This is the expected non-finding for an experimental overview paper that reports an external model application.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available; no explicit free parameters, axioms, or invented entities are identifiable. The Daemonflux model is referenced as an external input but its internal assumptions are not detailed.

pith-pipeline@v0.9.0 · 5581 in / 1193 out tokens · 69080 ms · 2026-05-09T19:35:25.072387+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

14 extracted references

[1]

Adrian-Martinez et al.J

S. Adrian-Martinez et al.J. Phys. G, 43:084001, 2016

2016
[2]

Aiello et al.JINST, 17:P07038, 2022

S. Aiello et al.JINST, 17:P07038, 2022

2022
[3]

D. Heck, J. Knapp, J. N. Capdevielle, G. Schatz, and T. Thouw. 2 1998

1998
[4]

Aiello et al.Eur

S. Aiello et al.Eur. Phys. J. C, 84:696, 2024

2024
[5]

Aiello et al.Eur

S. Aiello et al.Eur. Phys. J. C, 85:871, 2025

2025
[6]

Juan Pablo Ya˜ nez and Anatoli Fedynitch.Phys. Rev. D, 107:123037, 2023

2023
[7]

Becherini, A

Y. Becherini, A. Margiotta, M. Sioli, and M. Spurio.Astropart. Phys., 25:1–13, 2006

2006
[8]

Carminati, A

G. Carminati, A. Margiotta, and M. Spurio.Comput. Phys. Commun., 179:915–923, 2008

2008
[9]

PoS, ICRC2025:459, 2025

Br´ ıan´O Fearraigh, Venugopal Ellajosyula, Andrey Romanov, and Vladimir Kulikovskiy. PoS, ICRC2025:459, 2025

2025
[10]

Contribution 306, 20th TeVPa International Conference, 2025

Venugopal Ellajosyula et al. Contribution 306, 20th TeVPa International Conference, 2025

2025
[11]

Andrey Romanov and Valentin Pestel.PoS, ICRC2025:1158, 2025

2025
[12]

Amani Bemsa Bouasla and Reda Attallah.PoS, ICRC2025:202, 2025

2025
[13]

Piotr Kalaczy´ nski and Br´ ıan´O Fearraigh.PoS, ICRC2025:1071, 2025

2025
[14]

Aiello et al.Eur

S. Aiello et al.Eur. Phys. J. C, 83(4):344, 2023

2023