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arxiv: 1907.09197 · v1 · pith:L6WQ37GQnew · submitted 2019-07-22 · 🌌 astro-ph.IM

Muon calibration of the ASTRI-Horn telescope: preliminary results

T. Mineo , M. C. Maccarone , A. Compagnino , M. Capalbi , O. Catalano , G. Contino , D. Impiombato , P. Sangiorgi
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S. Garozzo D. Marano V. Conforti
This is my paper

Pith reviewed 2026-05-24 18:16 UTC · model grok-4.3

classification 🌌 astro-ph.IM
keywords muon calibrationASTRI-HornCherenkov telescopeSSTSiPMatmospheric showersCORSIKAtelescope calibration
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The pith

Muon events detected in 2018-2019 data confirm that the ASTRI-Horn telescope can be calibrated using atmospheric muons.

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

The paper tests whether muon-induced atmospheric showers can calibrate the relatively small ASTRI-Horn SST despite its four-meter primary mirror. Simulations with CORSIKA and a dedicated telescope response model predicted that such events should produce detectable Cherenkov signals on the SiPM-covered focal plane. Examination of regular science data from December 2018 and March 2019 identified events whose light distributions and timing properties match the simulated predictions. The match establishes that muon calibration is feasible for this dual-mirror telescope during normal operations.

Core claim

The central claim is that muon events recorded by ASTRI-Horn in December 2018 and March 2019 data match the output of CORSIKA atmospheric-shower simulations combined with a dedicated telescope simulator, thereby validating the simulations and confirming the feasibility of calibrating the ASTRI-Horn SST with muons.

What carries the argument

Muon-induced Cherenkov light flashes recorded on the curved SiPM focal surface of the dual-mirror SST, compared against CORSIKA plus dedicated simulator predictions to test the instrument response model.

If this is right

  • Calibration can be performed continuously using naturally occurring muons without external light sources or dedicated runs.
  • The telescope's optical alignment, mirror reflectivity, and front-end electronics response can be monitored during regular gamma-ray observations.
  • The same muon-based method becomes available for other small-sized telescopes planned for the Cherenkov Telescope Array.
  • Energy-scale and point-spread-function uncertainties in gamma-ray analyses can be cross-checked against an independent muon-derived reference.

Where Pith is reading between the lines

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

  • Muon calibration may allow direct comparison of response across telescopes of different mirror sizes within the same array.
  • Long-term accumulation of muon events could track slow degradation of SiPM quantum efficiency or mirror coatings.
  • If the method proves stable, it could reduce reliance on nightly laser or LED calibration runs for small telescopes.

Load-bearing premise

The selected events are produced by genuine muon showers rather than by other particles or instrumental artifacts.

What would settle it

A quantitative comparison in which the observed distributions of total light yield, pixel hit patterns, or arrival-time spreads differ significantly from the simulated distributions at the level of the reported uncertainties.

Figures

Figures reproduced from arXiv: 1907.09197 by A. Compagnino, D. Impiombato, D. Marano, G. Contino, M. Capalbi, M. C. Maccarone, O. Catalano, P. Sangiorgi, S. Garozzo, T. Mineo, V. Conforti.

Figure 1
Figure 1. Figure 1: Example of ring image in p.e., after the cleaning and a Gaussian smoothing over 3 pixels. The best fit circle is indicated with the white circle. Radial profile: Since Cherenkov signal from muons is intrinsically narrow [1], the width of the detected rings are then determined only by the optics PSF. Each radial profile, accumulated with a step of 0.5 pixel, was fitted with a Gaussian whose centre is the ri… view at source ↗
Figure 2
Figure 2. Figure 2: Best fit value of the ring width fitted with a Gaussian. The vertical blue line indicates the measured optics PSF. The distribution of telescope efficiency, computed as the ratio between the detected p.e. and the photons hitting the primary mirror, was obtained selecting high-quality events (ξ ≤ 2 and χ 2 ≤ 1 in the fit of the light along the ring) for a robust result. We found that the efficiency peaks at… view at source ↗
Figure 3
Figure 3. Figure 3: Telescope efficiency measured with the muon analysis in December 2018 and in March 2019. 5. Conclusion We presented a preliminary analysis of muons events detected by ASTRI-Horn during the tele￾scope verification phase. We confirmed the significant detection of the mirror reflectivity degrada￾tion in the March 2019 observation after a strong Etna eruption. The analysis is expected to improve using all data… view at source ↗
read the original abstract

Astri-Horn is a Small-Sized Telescope (SST) for very-high energy gamma-ray astronomy installed in Italy at the INAF "M.C. Fracastoro" observing station (Mt. Etna, Sicily). The ASTRI-Horn telescope is characterized by a dual-mirror optical system and a curved focal surface covered by SiPM sensors managed by a innovative fast front-end electronics. Dedicated studies were performed to verify the feasibility of the calibration through muons on the relatively small size of the primary mirror (~4 m diameter), as in the case of larger Cherenkov telescopes. A number of tests were performed using simulations of the atmospheric showers with the CORSIKA package and of the telescope response with a dedicated simulator. In this contribution we present a preliminary analysis of muon events detected by ASTRI-Horn during the regular scientific data taking performed in December 2018 and March 2019. These muon events validate the results obtained with the simulations and definitively confirm the feasibility of calibrating the ASTRI-Horn SST telescope with muons.

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 describes the ASTRI-Horn dual-mirror SST and reports a preliminary analysis of muon events recorded during scientific data taking in December 2018 and March 2019. Simulations of atmospheric showers are performed with CORSIKA and the telescope response is modeled with a dedicated simulator; the observed muon events are stated to validate the simulation results and to confirm the feasibility of muon-based calibration for this ~4 m telescope.

Significance. Demonstrating a practical muon-calibration path for small Cherenkov telescopes would be useful for the CTA SST array. The manuscript correctly identifies the size-related challenge and adopts the standard simulation-plus-data comparison strategy; however, the absence of quantitative agreement metrics limits the immediate impact of the result.

major comments (2)
  1. [Data analysis] Data-analysis section: no event-selection cuts, ring-parameter definitions, or background-rejection criteria are supplied for the December 2018/March 2019 data sets, preventing evaluation of whether the selected events are genuine muon showers and whether the claimed validation is robust.
  2. [Results] Results section: the comparison between data and CORSIKA+dedicated-simulator output is presented without any quantitative measures (e.g., Kolmogorov-Smirnov statistics, residual distributions, or light-yield ratios), so the strength of the validation statement cannot be assessed.
minor comments (1)
  1. [Abstract] Abstract: 'a innovative fast front-end electronics' should read 'an innovative fast front-end electronics'.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed and constructive report. The two major comments identify genuine gaps in the current preliminary manuscript. We will revise the text to address both points and strengthen the presentation of the muon-calibration results.

read point-by-point responses

  1. Referee: [Data analysis] Data-analysis section: no event-selection cuts, ring-parameter definitions, or background-rejection criteria are supplied for the December 2018/March 2019 data sets, preventing evaluation of whether the selected events are genuine muon showers and whether the claimed validation is robust.

    Authors: We agree that the absence of explicit selection criteria prevents a full assessment of the muon sample. In the revised manuscript we will add a new subsection under Data Analysis that defines the ring-fitting algorithm, the numerical cuts applied to the ring radius, width, and intensity, and the background-rejection procedure used for both the December 2018 and March 2019 data sets. These additions will allow readers to judge the purity of the selected muon events. revision: yes

  2. Referee: [Results] Results section: the comparison between data and CORSIKA+dedicated-simulator output is presented without any quantitative measures (e.g., Kolmogorov-Smirnov statistics, residual distributions, or light-yield ratios), so the strength of the validation statement cannot be assessed.

    Authors: We concur that quantitative metrics are required to substantiate the validation claim. The revised Results section will include Kolmogorov-Smirnov tests on the distributions of reconstructed ring radius and width, residual plots between data and simulation, and the measured light-yield ratio (data/simulation) with its uncertainty. These statistics will be computed from the same event samples already shown in the figures. revision: yes

Circularity Check

0 steps flagged

No circularity: validation is independent data-simulation comparison

full rationale

The paper reports preliminary detection of muon events in December 2018 and March 2019 data, compares their properties to CORSIKA atmospheric-shower simulations plus a dedicated telescope-response simulator, and concludes that the match validates muon calibration feasibility for the ASTRI-Horn SST. No equations, fitted parameters, or definitions are presented that reduce the target result to the inputs by construction. The comparison uses external observational data against simulation outputs whose assumptions are stated independently of the present dataset. Self-citations, if present for prior feasibility studies, are not load-bearing for the central claim, which remains externally falsifiable. This is a standard empirical validation workflow with no reduction to self-definition or renaming.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review; no explicit free parameters, axioms, or invented entities are stated in the provided text. Full manuscript would be required to identify any simulation tuning constants or modeling assumptions.

pith-pipeline@v0.9.0 · 5766 in / 1009 out tokens · 23210 ms · 2026-05-24T18:16:42.628875+00:00 · methodology

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Reference graph

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