{"id":"b7476cd1-5565-4ee1-88f1-852f25d0059b","arxiv_id":"2412.15154","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"low","formal_verification":"none","parameter_count":0,"one_line_summary":"ProtoDUNE-HD's X-Arapuca photon detection system ran stably, and its measured scintillation timing and light yield agree with expectations.","lead":"This paper reports the first performance results of the photon detection system of ProtoDUNE-HD, a 750-ton liquid argon prototype for DUNE. It shows the detector ran stably for months and that light yield scales with beam energy, supporting the DUNE far detector design.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The central linearity claim rests on an uncorrected raw light-vs-beam-energy plot (Sec. 2.3), so the apparent proportionality could be produced by momentum-dependent beam composition, trigger acceptance, or backgrounds; the stability and tau_slow claims are not affected.","rationale":"I agree with the reader's weakest_assumption. Section 2.3's explicit no-cuts caveat is the key limitation, and the linearity figure is the only quantitative performance result tied to physics expectations. The abstract and conclusions repeat the linearity expectation, so the paper's central claim depends on it. However, the stable-operation and tau_slow measurements are independent and credible as preliminary system performance: VBR weekly monitoring, LED gain calibration, and a two-exponential fit are standard, and the field-on reduction from about 1.5 to about 1.3 microseconds is consistent with previous measurements. Thus I would not reject or downgrade beyond CONDITIONAL; the necessary condition is a corrected analysis. My concern is the same as the reader's, and no additional load-bearing issue emerged. The lack of error bars and the minimal text around the figures make the report hard to fully audit, but that is a presentation limitation, not an internal inconsistency.","tokens_in":3542,"tokens_out":2989,"duration_ms":34247,"concrete_test":"Use the ProtoDUNE-HD 2024 beam dataset, select beam-triggered events with one reconstructed TPC track fully contained in the fiducial volume, identify each event's particle species via dE/dx and calorimetry, correct each momentum bin for trigger efficiency and subtract cosmic/out-of-time backgrounds, and recompute the mean integrated PDS charge versus beam energy. If the corrected points remain on a straight line through the origin, the raw linearity claim is confirmed; if the slope changes across the 0.5-7 GeV/c range, the original no-cut plot was masking an instrumental correlation and the paper's linearity statement must be qualified.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The paper's performance claim includes 'linearity of the detected light with the particle energy is in agreement with the expectations.' Section 2.3 states explicitly 'At this stage, no cuts have been applied' for the left panel of Figure 3. The x-axis is the beam momentum set by the beamline, and the y-axis is the integrated PDS signal summed over all triggered events. Without event selection, the sample mixes electrons, protons, pions, kaons, and muons, whose proportions vary with momentum. Different particle species deposit energy in very different ways: electrons shower, pions and protons can interact inelastically, and muons are minimum-ionizing. The integrated light per beam particle is therefore not simply proportional to beam energy unless the beam composition and detector acceptance are momentum-independent or corrected. Trigger efficiency and out-of-time cosmic/beam backgrounds can also vary with momentum and would add an instrumental trend. Thus the agreement with expectations for linearity is not yet evidence for calorimetric linearity. The tau_slow and VBR stability measurements are more robust because they rely on per-channel calibration and monitoring, although no systematic uncertainties are reported. This is explicitly a preliminary report, so the lack of corrections is not a soundness error, but it makes the linearity conclusion load-bearing and currently undemonstrated.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This proceedings paper reports the preliminary performance of the ProtoDUNE-HD Photon Detection System (PDS) during the 2024 run. The PDS, based on 160 X-Arapuca modules read out by SiPMs and DAPHNE electronics, was operated from April to November 2024. The paper presents three main results: weekly SiPM breakdown-voltage monitoring showing stable operation, a measurement of the slow scintillation decay time tau_slow (about 1.5 microseconds without drift field and about 1.3 microseconds at 0.5 kV/cm), and a preliminary plot of integrated PDS light versus beam energy that is described as showing good linearity. The paper concludes that the PDS operated stably and that the tau_slow and linearity measurements are in agreement with expectations.","tokens_in":3801,"tokens_out":2610,"duration_ms":24571,"significance":"If the results hold, this paper provides an important large-scale validation of the X-Arapuca-based photon detection approach for the DUNE Far Detector. Its strengths are direct operational data from a 750-ton prototype over several months, a concrete per-channel calibration procedure for breakdown voltage and gain, and explicit comparison of tau_slow and drift-field dependence with previously published measurements. The paper is honest in labeling all results as preliminary. However, the significance is limited by the absence of quantitative uncertainties and by the fact that the linearity claim rests on an uncorrected raw-data plot.","major_comments":[{"comment":"The central linearity claim is not yet supported by the presented data. The left panel of Figure 3 plots the integrated PDS signal as a function of beam momentum for a mixed beam (electrons, protons, pions, kaons, muons) with no event selection, background subtraction, or trigger-efficiency correction, as the paper itself states: 'At this stage, no cuts have been applied.' Because the beam composition and the probability of inelastic interactions vary with momentum, the observed linear trend could be produced by momentum-dependent acceptance and backgrounds rather than by calorimetric linearity of the PDS. The conclusion in Section 3 that 'the linearity of the detected light with the particle energy is in agreement with the expectations' is therefore premature. I recommend either applying appropriate particle-identification and fiducial cuts, correcting for trigger efficiency, or explicitly rephrasing the claim as a raw-signal trend that is not yet a measurement of energy linearity.","section":"Section 2.3 / Figure 3 left"},{"comment":"The tau_slow measurement is presented without fit uncertainties or systematic checks. The text quotes values of about 1.5 microseconds and 1.3 microseconds and claims agreement with expectations and with previous measurements, but no errors are given for the extracted decay times, and the dependence on the choice of the two-exponential convolution model, the fit range, or the selected channels is not discussed. Since the agreement with expectations is one of the paper's two headline physics results, I would like to see at least a statistical uncertainty on the quoted tau_slow values and a brief statement of the dominant systematic effects, or the claim should be explicitly labeled as a qualitative preliminary observation.","section":"Section 2.2 / Figure 2"}],"minor_comments":[{"comment":"The abbreviation 'SiPM' is written as 'SIPM' in at least one place; please use a consistent capitalization throughout (e.g., 'SiPM' as in the abstract).","section":"Section 2"},{"comment":"The phrase 'LAr-TPCS' should be 'LAr-TPCs' for correct pluralization.","section":"Section 1"},{"comment":"The phrase 'under the presence of the drift field' is awkward; consider 'in the presence of the drift field' or 'with the drift field applied.'","section":"Section 2.2"},{"comment":"The caption states that the spike at the end of July 'corresponds to a drift-field scan'; please specify the range of drift fields used during that scan, as this is relevant for interpreting the observed tau_slow variation.","section":"Figure 2 caption"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a short conference proceedings, so the level of detail is appropriate for a preliminary report. The main concern is that the linearity claim, which appears in the abstract and conclusions, is based on an uncorrected mixed-beam plot. This is fixable either by adding basic corrections or by softening the claim, and I would not require a full analysis in this venue. The tau_slow and stability measurements are more robust, though quantitative uncertainties would strengthen the paper."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a genuine first public look at the ProtoDUNE-HD PDS from the 2024 run, and it does what a good prototype report should: it shows stable operation, careful SiPM calibration, and a tau_slow measurement consistent with high-purity LAr. The paper is honest about being preliminary, and the figures back the qualitative claims.\n\nThe new things here are the 2024 data: weekly VBR monitoring across the run, the tau_slow evolution from ~1.5 us to ~1.3 us when the drift field is turned on, and the raw light-vs-beam-energy trend from 0.5 to 7 GeV/c. None of these individually break new physics, but as a validation of the X-Arapuca PDS at 750-ton scale they matter for DUNE. The lab characterizations in refs [5,6] are cited properly, and the observed drift-field reduction is compared to earlier DUNE and WA105 results [8,9]. I see no circularity.\n\nThe soft spot is exactly where the stress-test note points: Section 2.3 claims linearity from a plot with no event selection, no background subtraction, and no trigger-efficiency correction. The beam mixes electrons, pions, protons, kaons, and muons with momentum-dependent fractions, so the integrated light per beam particle is not a clean calorimetric estimator. The agreement with 'expectations' could be accidental to the mix. That said, the paper explicitly labels these results preliminary and the stability and tau_slow parts do not rely on that plot. The tau_slow extraction uses a two-exponential convolution; I would have liked a systematic check on the fit range or the SPE response, but the values are consistent with external measurements and the trend with field is physical.\n\nThe main limitation is that this is a four-page proceedings note, so no uncertainties are quoted on the linearity slope, no efficiency corrections, and no event classes. That is normal for a conference contribution, but a reader should not take the linearity claim as a measured result until a full analysis appears.\n\nWho is this for? DUNE collaborators, LArTPC detector folks, and anyone tracking PDS performance. It deserves a serious referee if submitted as a proceedings paper; the data are real and the presentation is honest. I would not cite it in a physics paper yet because the results are preliminary and unquantified, but I would point people to it as the status of the PDS validation.\n\nRecommendation: engage with it, send to review as it is a legitimate detector performance note. Just keep the linearity claim in perspective.","headline":"A straight, honest preliminary report from ProtoDUNE-HD that validates stable PDS operation and purity monitoring; the linearity claim is real but currently rests on an uncorrected raw plot.","tokens_in":4300,"tokens_out":2240,"would_cite":false,"duration_ms":20098,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"ProtoDUNE-HD's X-Arapuca photon detection system ran stably through the 2024 run, and preliminary light-yield versus beam energy is linear as expected.","keywords":["ProtoDUNE-HD","Photon Detection System","X-Arapuca","liquid argon TPC","silicon photomultiplier","scintillation light","tau_slow","DUNE"],"falsifier":"Recompute the light-yield versus beam-energy relation after applying event selection, background subtraction, and trigger-efficiency corrections, and check whether the slope is stable across beam momentum bins; if the relation becomes non-linear or moves with beam composition, the linearity claim fails. For the purity claim, verify that the reported $\\tau_{\\mathrm{slow}}$ values at 0 and 0.5 kV/cm reproduce the literature drift-field dependence when the nitrogen equivalent is held fixed.","tokens_in":3367,"feed_emoji":"💡","tokens_out":9403,"duration_ms":75126,"temperature":0.7,"pith_summary":"This paper reports on the first large-scale deployment of the X-Arapuca photon detection system in ProtoDUNE-HD, and claims that the system operated stably during the 2024 data-taking run from April to November. Two preliminary physics results are presented: the slow scintillation decay time is measured as about 1.5 $\\mu$s without the drift field and 1.3 $\\mu$s with the 0.5 kV/cm field, corresponding to roughly 0.48 ppm nitrogen contamination, and the integrated detected light is proportional to beam energy between 0.5 and 7 GeV/c. The author states that both results are in agreement with expectations and that no cuts have been applied to the light-yield sample. The stakes are that this is the validation step for the X-Arapuca-based photon detection design chosen for the DUNE far detector.","feed_headline":"ProtoDUNE photon detector stayed stable through 2024 run","feed_subtitle":"Preliminary light-vs-energy linearity and argon purity match expectations, backing the X-Arapuca design for DUNE.","key_machinery":"The load-bearing object is the X-Arapuca, a photon trap that combines wavelength-shifting materials and dichroic filters to capture 127 nm vacuum-ultraviolet scintillation light from liquid argon, re-emit it in the visible range, and concentrate it onto silicon photomultipliers. ProtoDUNE-HD carries 160 such modules in four configurations (two wavelength-shifter manufacturers and two SiPM models). The stability and performance claims are carried by three tools: periodic current-voltage scans that locate the SiPM breakdown voltage, an LED pulsing system that monitors gain and signal-to-noise, and fits of averaged waveforms to two exponentials convolved with the single-photon response to extract $\\tau_{\\mathrm{slow}}$.","core_discovery":"On its own terms, the paper establishes that the ProtoDUNE-HD Photon Detection System -- 160 X-Arapuca modules placed behind four anode planes, each module reading out 48 ganged SiPMs -- ran stably for the entire 2024 run, with weekly current-voltage scans of breakdown voltage and LED-based gain calibrations staying under control. For physics performance, it reports two preliminary measurements: a fit of the average scintillation waveform to the sum of two exponentials convolved with the single-photon response gives $\\tau_{\\mathrm{slow}} \\approx 1.5\\,\\mu\\mathrm{s}$ without drift field and $\\approx 1.3\\,\\mu\\mathrm{s}$ at 0.5 kV/cm, and the integrated PDS signal versus beam energy shows good linearity over the full momentum range. The paper notes explicitly that no cuts have been applied in that comparison, and concludes both results are in agreement with expectations.","pith_inferences":["Beyond the paper's text: the no-cuts linearity plot could be shaped by momentum-dependent trigger efficiency or beam composition changes, so the definitive statement about light-energy proportionality awaits the analysis with full event selection.","Because the detector exposes four X-Arapuca variants (Eljen vs G2P wavelength shifters, HPK vs FBK SiPMs) under identical beam conditions, an in situ efficiency ranking is a natural next step for choosing far-detector modules.","The drop of $\\tau_{\\mathrm{slow}}$ when the drift field is turned on implies that purity monitoring at fixed field is the correct operational mode; future runs could use the PDS to look for time or field-dependent changes in the recombination response."],"forward_implications":["If the stability persists over the full dataset, the X-Arapuca plus DAPHNE readout chain is a workable basis for the DUNE far detector PDS.","If the $\\tau_{\\mathrm{slow}}$ values survive refinement, the PDS can act as an online argon-purity monitor, with the measured 0.48 ppm nitrogen equivalent sitting where expected.","If the light-yield linearity holds after event selection and background subtraction, the PDS provides an independent calorimetric energy estimate for beam and cosmic interactions.","The observed decrease of detected light with drift field, consistent with the recombination picture, gives a calibration handle for photon production in the far detector."],"supporting_citations":[{"why":"Introduces the X-Arapuca concept that the entire ProtoDUNE-HD PDS is based on.","marker":"[4]"},{"why":"Provides laboratory photon detection efficiency measurements for the four X-Arapuca configurations, including the G2P+HPK combination reported as best.","marker":"[5]"},{"why":"Documents the extensive SiPM laboratory characterization used to select and monitor the modules.","marker":"[6]"},{"why":"Describes the DAPHNE readout electronics that digitize and trigger the SiPM channels.","marker":"[7]"},{"why":"Supplies the earlier measurement of tau_slow reduction under drift field that the new values are compared with.","marker":"[8]"},{"why":"Also reports the drift-field dependence of tau_slow in liquid argon, providing the expectation the paper matches.","marker":"[9]"}],"fun_headline_variants":["ProtoDUNE photon detector stable all 2024 run","Light-energy linearity holds in ProtoDUNE PDS","ProtoDUNE PDS: stable, linear, matches expectations"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The linearity result rests on the assumption that the uncut data sample is representative, since the paper states that no event selection, background subtraction, or trigger-efficiency correction has been applied at this stage.","fun_headline_variants_meta":{"raw":{"variants":["ProtoDUNE photon detector stable all 2024 run","Light-energy linearity holds in ProtoDUNE PDS","ProtoDUNE PDS: stable, linear, matches expectations"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000207,"raw_usage":{"total_tokens":1392,"prompt_tokens":928,"completion_tokens":464,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":544,"completion_tokens_details":{"reasoning_tokens":410}},"tokens_in":544,"tokens_out":464,"duration_ms":4142,"temperature":1.0,"reasoning_tokens":410,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T11:33:37.181214+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Recompute the light-yield versus beam-energy relation after applying event selection, background subtraction, and trigger-efficiency corrections, and check whether the slope is stable across beam momentum bins; if the relation becomes non-linear or moves with beam composition, the linearity claim fails. For the purity claim, verify that the reported $\\tau_{\\mathrm{slow}}$ values at 0 and 0.5 kV/cm reproduce the literature drift-field dependence when the nitrogen equivalent is held fixed.","supporting_citations":[{"cited_title":"Measurement of the absolute efficiency of the X-ARAPUCA photon detector for the DUNE Far Detector 1","cited_arxiv_id":"2405.12014","evidence_quote":"Supplies the earlier measurement of tau_slow reduction under drift field that the new values are compared with."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Also reports the drift-field dependence of tau_slow in liquid argon, providing the expectation the paper matches."}],"review_version":1}