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arxiv: 2512.10790 · v3 · submitted 2025-12-11 · ✦ hep-ex · physics.ins-det

Modeling Light Signals Using Data from the First Pulsed Neutron Source Program at the DUNE Vertical Drift ColdBox Test Facility at CERN Neutrino Platform

A. Paudel , W. Shi , P. Sala , F. Cavanna , W. Johnson , J. Wang , W. Ketchum , F. Resnati
show 31 more authors
A. Heindel A. Ashkenazi E. Bertholet E. Bertolini D. A. Martinez Caicedo E. Calvo A. Canto S. Manthey Corchado C. Cuesta Z. Djurcic M. Fani A. Feld S. Fogarty F. Galizzi S. Gollapinni Y. Kerma\"idic A. Kish F. Marinho D. Torres Mu\~noz A. Verdugo de Osa L. Paulucci W. Pellico V. Popov J. Rodriguez Rondon D. Leon Silverio S. Sacerdoti H. Souza R. C Svoboda D. Totani V. Trabattoni L. Zambelli
This is my paper

Pith reviewed 2026-05-16 23:04 UTC · model grok-4.3

classification ✦ hep-ex physics.ins-det
keywords LArTPCpulsed neutron sourcelight signalsFluka simulationX-ARAPUCAphotoelectronsvertical driftCERN neutrino platform
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The pith

Neutron beam data from a small vertical-drift LArTPC at CERN matches Fluka simulations of detected light signals, with photoelectron counts below 650 in both and consistent time constants.

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

The paper tests a Fluka-based model of light production and detection by running a pulsed neutron source inside a vertical-drift liquid-argon time-projection chamber at the CERN neutrino platform ColdBox facility. The entire setup—cryostat, neutron sources, particle interactions, and four X-ARAPUCA photodetectors mounted on the cathode—is simulated, then compared directly to the measured light signals. Data and simulation both record fewer than 650 photoelectrons per event, and a fitted time constant extracted from the neutron-beam-off spectrum agrees between measurement and Monte Carlo. Several systematic effects are identified that will affect scaling to larger detectors.

Core claim

Simulations using Fluka of the ColdBox cryostat, detectors, neutron sources, and particle interactions reproduce the detected light signals from a pulsed neutron source in a vertical drift LArTPC, with the number of photoelectrons in data and simulation both remaining below 650 for all four X-ARAPUCA photodetectors on the cathode, and with the fitted time constant from the neutron-beam-off spectrum consistent between measurement and Monte Carlo.

What carries the argument

Fluka Monte Carlo model of neutron-induced scintillation light production, transport, and detection in the LArTPC geometry with X-ARAPUCA photodetectors.

If this is right

  • Neutron-induced light signals in this LArTPC scale remain below 650 photoelectrons and are predictable by the simulation.
  • The time structure of light signals without the neutron beam can be extracted consistently from both data and Monte Carlo.
  • Identified systematic effects provide concrete guidance for modeling light in future larger vertical-drift LArTPCs.
  • The same simulation framework can be applied to predict light backgrounds and signal efficiencies in scaled-up detectors.

Where Pith is reading between the lines

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

  • If the agreement holds at larger scales, similar neutron calibration runs could become a standard validation tool for light models in full-size DUNE modules.
  • The work suggests that beam-off time constants may serve as a useful diagnostic for scintillation properties independent of the neutron source.
  • Extending the same geometry modeling to include additional photodetector placements could test whether cathode-mounted sensors remain optimal at larger drift distances.
  • The identified systematics point to a need for dedicated runs that vary neutron energy or beam timing to isolate individual uncertainty sources.

Load-bearing premise

The Fluka modeling of neutron sources, particle interactions, light production, and detector geometry accurately captures the physical processes occurring inside the LArTPC.

What would settle it

A data set in which the measured photoelectron yield per event deviates by more than a few tens of percent from the simulated yield below 650, or in which the fitted beam-off time constant differs significantly from the Monte Carlo value, would falsify the reported agreement.

read the original abstract

In this paper, we present a first quantitative test of detected light signals produced in a pulsed neutron source run in a small vertical drift LArTPC at the CERN neutrino platform ColdBox test facility. The ColdBox cryostat, detectors, neutron sources, and particle interactions are modeled and simulated using Fluka. A good agreement is found in the detected number of photoelectrons, with values below 650 photoelectrons in both data and simulation, for all four X-ARAPUCA photodetectors on the cathode in the LArTPC. A time constant is also fitted from the neutron-beam-off light signal spectrum and found consistent between data and MC. Several important systematic effects are discussed and serve as guides for future runs at larger LArTPCs.

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 / 2 minor

Summary. The manuscript reports a first quantitative comparison of detected light signals from a pulsed neutron source in a small vertical-drift LArTPC at the CERN Neutrino Platform ColdBox facility. Using Fluka to model the cryostat, detectors, neutron sources, particle interactions, scintillation, and photon detection, the authors find that both data and simulation yield fewer than 650 photoelectrons in each of the four X-ARAPUCA photodetectors on the cathode, and that a time constant fitted to the neutron-beam-off light spectrum is consistent between data and Monte Carlo.

Significance. If the reported agreement survives detailed scrutiny of the modeling chain and uncertainties, the work supplies a valuable benchmark for neutron-induced scintillation and light collection in LArTPCs. It is the first such test in the DUNE vertical-drift geometry and explicitly flags systematic effects that will matter for larger detectors, thereby strengthening the physics case for light-based calorimetry and triggering in DUNE.

major comments (2)
  1. [Modeling and Simulation] The quantitative agreement (photoelectron yield <650 PE and consistent time constant) rests on the accuracy of the full Fluka chain—neutron transport, hadronic interactions, LAr scintillation yield and quenching, photon propagation, and X-ARAPUCA PDE—yet the manuscript provides no independent cross-checks of intermediate steps such as energy-deposition spectra or light-yield normalization in this geometry. Compensating errors could produce the observed match without validating the underlying physics.
  2. [Results] The abstract and results section state that systematic effects are discussed, but the manuscript does not supply the quantitative breakdown of uncertainties, data-selection cuts, or error-propagation procedure used to establish the claimed agreement on photoelectron yield and the fitted time constant. Without these, the strength of the central claim cannot be assessed.
minor comments (2)
  1. [Abstract] The fitted time-constant value itself is not quoted numerically in the abstract or summary; including the central value and uncertainty would allow readers to judge the degree of consistency immediately.
  2. [Figures] Figure captions and axis labels should explicitly state whether the plotted photoelectron spectra are normalized or absolute, and whether the beam-off spectrum used for the time-constant fit includes any background subtraction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive evaluation of the work's significance and for the detailed comments on the simulation chain and uncertainty quantification. We address each major comment below and have revised the manuscript to strengthen the presentation of the modeling validation and the quantitative treatment of systematics.

read point-by-point responses

  1. Referee: [Modeling and Simulation] The quantitative agreement (photoelectron yield <650 PE and consistent time constant) rests on the accuracy of the full Fluka chain—neutron transport, hadronic interactions, LAr scintillation yield and quenching, photon propagation, and X-ARAPUCA PDE—yet the manuscript provides no independent cross-checks of intermediate steps such as energy-deposition spectra or light-yield normalization in this geometry. Compensating errors could produce the observed match without validating the underlying physics.

    Authors: We agree that explicit cross-checks of intermediate steps would strengthen the claim. The revised manuscript now includes a new subsection describing the validation of the Fluka neutron transport and hadronic models against published LAr data, together with a figure comparing the simulated energy-deposition spectrum in the active volume to the expected distribution from the pulsed source. We also add a brief discussion of the LAr scintillation yield and quenching parameters adopted from the literature and note that this measurement constitutes the first direct benchmark in the vertical-drift geometry. While full independent experimental cross-checks for every sub-process were not feasible in this small-scale test, the added material reduces the possibility of undetected compensating errors. revision: partial

  2. Referee: [Results] The abstract and results section state that systematic effects are discussed, but the manuscript does not supply the quantitative breakdown of uncertainties, data-selection cuts, or error-propagation procedure used to establish the claimed agreement on photoelectron yield and the fitted time constant. Without these, the strength of the central claim cannot be assessed.

    Authors: We accept this criticism. The revised results section now contains an expanded table that quantifies the dominant systematic uncertainties (neutron source intensity, LAr purity variations, X-ARAPUCA PDE calibration, and optical property uncertainties), lists the explicit data-selection cuts applied to the light waveforms, and describes the error-propagation procedure used for both the photoelectron yield and the fitted time constant. These additions allow a direct assessment of the robustness of the reported agreement. revision: yes

Circularity Check

0 steps flagged

No significant circularity; direct data-simulation comparison with independent fit

full rationale

The paper models the ColdBox, neutron sources, and LArTPC with Fluka, then compares simulated photoelectron counts directly to measured data (both <650 pe for the four X-ARAPUCA detectors). A time constant is fitted from the neutron-beam-off spectrum in data and checked for consistency in MC without being imposed by the simulation. No equation or claim reduces by construction to its own inputs, no fitted parameter is relabeled as a prediction, and no load-bearing step relies on self-citation chains. The derivation is self-contained against external experimental benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The claim rests on the accuracy of the Fluka Monte Carlo package for neutron-argon interactions and scintillation light production, plus the geometric model of the ColdBox cryostat and X-ARAPUCA sensors. No new free parameters are introduced beyond the fitted time constant extracted from data.

free parameters (1)
  • fitted time constant
    Extracted from the neutron-beam-off light signal spectrum in both data and MC; used to quantify consistency rather than to tune the central prediction.
axioms (1)
  • domain assumption Fluka accurately models neutron-induced scintillation and light propagation in liquid argon
    Invoked when the simulation is compared directly to data without additional tuning parameters.

pith-pipeline@v0.9.0 · 5642 in / 1251 out tokens · 40079 ms · 2026-05-16T23:04:47.267448+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Enhanced Reconstruction of Sub-GeV Neutrinos Charged Current Interactions in LArTPC

    hep-ex 2026-04 unverdicted novelty 5.0

    Combining charge and light signals in LArTPCs yields better sub-GeV energy reconstruction, 70% electron neutrino-antineutrino separation efficiency, and about 20-degree direction improvement for antineutrinos via neut...

Reference graph

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