{"id":"4535a836-974a-4798-9944-6892184ff6e4","arxiv_id":"1908.04620","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Using full waveform readout with a 9 ns peak-aligned integration window reduces noise and extends reconstructed image lengths for H.E.S.S. I, improving simulated effective area at low energies and promising similar gains at high energies.","lead":"Upgraded H.E.S.S. I cameras can now record full 1 GHz waveforms alongside the standard 16 ns charge integration, and this paper shows how a 9 ns integration around each pixel's peak reduces noise and avoids truncating long Cherenkov images. This could extend H.E.S.S. sensitivity at low and high gamma-ray energies, supporting searches for PeVatron sources.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Headline sensitivity gain rests on retraining the full analysis chain; the presented effective-area-only comparison cannot support the claim yet.","rationale":"The reader's weakest assumption identifies the same load-bearing concern: the projected sensitivity improvement is not a measured end-to-end result but an extrapolation that requires the still-ongoing retraining of the full analysis chain. I considered other potential concerns, such as a bias in pedestal estimation from the next-neighbour peak-finding algorithm, but concluded that the algorithm's design (using the neighbour-sum peak rather than the pixel's own peak) avoids a systematic pedestal bias for noise-only pixels, so that concern does not land. The dominant issue is the gap between the paper's headline claim of improved sensitivity and the presented evidence, which consists of an effective-area comparison with only an amplitude cut, a single illustrative event, and Hillas-length ratios. Because the paper itself repeatedly qualifies the high-energy and sensitivity gains as expected after ongoing optimization, the conditional verdict is appropriate. The proposed concrete test directly closes that gap by running the full analysis chain with retrained BDTs and ImPACT templates on the same simulations, which would either validate the extrapolation or reveal that the effective-area advantage is reduced or reversed after background rejection.","tokens_in":5876,"tokens_out":11435,"duration_ms":116810,"concrete_test":"Reproduce the analysis on the same simulated gamma and proton data sets used for Fig. 7, but with the full SM analysis chain: retrained boosted decision trees for gamma-hadron separation, newly produced ImPACT templates, the rescaled 3/7 p.e. tail cuts, and an analogous amplitude cut. Compare the resulting differential flux sensitivity (or the significance for a Crab-like source spectrum) between CM and SM as a function of energy. If the SM sensitivity is not better than CM at low energies, or if the gain is smaller than the effective-area gain in Fig. 7, then the central claim is not supported.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The abstract and title claim 'sensitivity improvements' from full waveform processing, but the quantitative support is an effective-area comparison (Fig. 7) that applies only a lower-image-amplitude cut (54 vs 60 p.e.) and releases all other cuts. Section 3 explicitly states that the optimization study to define new cuts, new Hillas settings, and new ImPACT templates 'is underway', and the Summary says the low-energy gain is 'shown' while the high-energy gain is only 'expected' once the full set of new analysis cuts and new boosted decision trees have been defined and re-trained for SM. The central claim therefore depends on the untested premise that retraining gamma-hadron separation and ImPACT reconstruction preserves the effective-area advantage. This is not guaranteed: the additional faint images that raise the low-energy effective area are also those most likely to be rejected as background by a BDT, and the 'enhanced reconstruction' at high energies is illustrated by a single simulated event (Fig. 5) and by Hillas-length ratios (Fig. 6) without any energy- or angular-resolution comparison. In short, the paper demonstrates reduced noise integration and increased Hillas length, but the leap from those observables to 'sensitivity' is supported only by expectation, not by an end-to-end analysis.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper reports on the sample mode (SM) of the upgraded H.E.S.S. I cameras, which reads out full 1 GHz-sampled waveforms in parallel to the nominal charge mode (CM). The authors introduce a next-neighbour peak-finding algorithm and extract charges by integrating over a fixed 9 ns window around the peak (SMMax9). They describe the integration of SM into the simulation, calibration, and analysis chains, and compare SM and CM on simulated events. The main quantitative results are: a CM/SM gain ratio of about 0.91; SM images that are generally longer in Hillas length, especially for high-impact-distance and low-energy events; and an effective area comparison (Fig. 7) with only a lower-image-amplitude cut applied, showing a higher effective area for SM at low energies and a similar effective area at high energies. The paper also reports first indications of improved angular resolution for high-offset, high-energy events. The abstract and title claim sensitivity improvements from full waveform processing, with the low-energy gain described as shown and the high-energy gain as expected once the full analysis chain is retrained.","tokens_in":6097,"tokens_out":4728,"duration_ms":48356,"significance":"If the claimed improvements hold, full waveform processing with SMMax9 extraction could lower the energy threshold of H.E.S.S. and improve the reconstruction of multi-TeV gamma-ray events, which is directly relevant to the study of PeVatron candidates. The paper's strengths include a plausible and well-motivated charge-extraction algorithm, its integration into the simulation chain via a gain ratio consistent with the SPE pulse shape, and validation on LED and observation runs. The qualitative claims about reduced noise integration and increased Hillas lengths are supported by the presented simulations. However, the central sensitivity claim is currently supported only by an effective-area comparison with a single amplitude cut, and the paper explicitly states that the optimization of the full analysis chain is underway. Thus the significance of the paper as a demonstration of a sensitivity improvement is not yet established.","major_comments":[{"comment":"The effective area comparison in Fig. 7 applies only a lower-image-amplitude cut (60 p.e. for CM and ~54 p.e. for SM) with all other cuts released, as stated in the text. Section 3 explicitly says that an optimisation study to define new cuts, new Hillas settings, and new ImPACT templates for SM is underway. Because gamma-hadron separation and direction/energy reconstruction are not applied, this comparison alone cannot support the abstract's claim of increased sensitivity. The additional faint images that raise the low-energy effective area are also the ones most likely to be rejected by a boosted decision tree, and the high-energy improvement is not visible in the effective area at all. The paper should either provide an end-to-end sensitivity estimate (including background rejection and reconstruction performance) or explicitly restrict the claim to an expected improvement based on effective area.","section":"Section 4, Fig. 7"},{"comment":"The title and abstract claim 'sensitivity improvements' from full waveform processing, but the body of the paper states that the optimization of the full analysis chain is still underway and that the high-energy gain is 'expected' once new cuts and boosted decision trees are retrained. The Summary states that increased statistics at the lower energy end 'was shown', which is stronger than what Fig. 7 demonstrates, since that figure uses only an amplitude cut and no background rejection. This mismatch between the headline claim and the presented evidence is load-bearing. The authors should either add a sensitivity calculation using the currently available effective area and a background model, or soften the title and abstract to 'expected sensitivity improvements' or 'improved effective area and image reconstruction in sample mode'.","section":"Section 5 (Summary) and title/abstract"},{"comment":"The SM image-cleaning tail cuts are set to 3 and 7 p.e. from the CM values of 5 and 10 p.e. using a scaling of sqrt(16/9) x 0.91, under the assumption that the noise is reduced by the shorter integration window and scaled by the gain ratio. This is a reasonable first estimate, but the paper does not demonstrate that these cut values preserve the same background rejection as the CM cuts. If the 3/7 p.e. cuts accept more night-sky-background or hadronic events, the increase in effective area could be offset by a larger background acceptance after gamma-hadron separation. The authors should validate this tail-cut choice with background simulations or with a comparison of background rates on data, or state explicitly that the final sensitivity depends on a re-optimization that is not yet complete.","section":"Section 4, tail-cut rescaling"}],"minor_comments":[{"comment":"The caption of Figure 5 refers to 'SMMax16' while the rest of the paper uses a 9 ns integration window (SMMax9). If the figure intentionally uses a 16 ns window to illustrate the full signal, this should be stated; otherwise it is an inconsistency that should be corrected.","section":"Figure 5 caption"},{"comment":"The text contains a typo: 'SM data readout is planed to be enabled' should be 'planned'.","section":"Section 2"},{"comment":"The phrase 'mis-identification of an night-sky-background photon' should read 'a night-sky-background photon'.","section":"Section 3"},{"comment":"The Hillas length ratio plots in Fig. 6 are 2D histograms with a color scale, but the text would be clearer if the average ratio and its uncertainty in each bin were given, particularly because the number of events per bin is not shown. This would help quantify the claim that images are 'in general' longer in SM.","section":"Section 4, Fig. 6"},{"comment":"The sentence 'A study about an improvement of energy and angular resolution is on-going' would read better as 'A study of the improvement in energy and angular resolution is ongoing'.","section":"Section 5"}],"recommendation":"major_revision","confidential_remarks":"This is a conference proceedings paper from a major collaboration, and the technical development described is plausible and of interest to the gamma-ray astronomy community. The main obstacle to acceptance in the current form is the mismatch between the title/abstract's claim of 'sensitivity improvements' and the evidence presented, which is limited to effective area with a single amplitude cut and the authors' own statement that the full optimization is underway. A major revision that either adds an end-to-end sensitivity estimate or carefully qualifies the claims as expected rather than demonstrated would resolve this issue. The paper may also benefit from a broader discussion of the systematic uncertainties in the simulation chain, particularly the validation of the simulated SM charge extraction against real data beyond the gain and image examples shown."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know two things about this ICRC proceedings. First, the genuinely new piece is the SMMax9 charge-extraction algorithm: a next-neighbor peak-time finder with a 9 ns integration window, and the authors show, with simulations and a few data cross-checks, that it lowers noise and yields longer Hillas images than the 16 ns fixed-window charge mode. Second, the title says 'sensitivity improvements', but the evidence is an effective-area comparison that applies only an image-amplitude cut; the full analysis chain—tail cuts, Hillas settings, ImPACT templates, boosted decision trees—has not yet been retrained for sample mode. The paper says this optimization 'is underway'.\n\nWhat is done well: the readout scheme and the integration into the calibration and simulation chains are clearly described. The NN peak-finding argument is sensible, and the use of LED flasher and muon-event checks gives some confidence that the algorithm works on real data. The gain ratio between CM and SM is checked against the SPE pulse shape, and the Hillas-length ratio plots show the expected lengthening at high impact distances and at low energies. The effective-area curve at low energy, with only an amplitude cut, is a legitimate first quantitative indication.\n\nThe soft spots are in the gap between what is shown and what the title claims. The high-energy improvement is illustrated with a single simulated event and length ratios; no energy or angular resolution comparison is shown yet, and the authors themselves say 'first results' on angular resolution suggest improvement. More important, the low-energy effective-area gain is exactly the population of faint images that a retrained gamma-hadron separator might reject. So the sensitivity gain is plausible but not yet demonstrated. That is not a circularity problem—the comparison is an internal simulation study, no result is fed back into the inputs—but it is a load-bearing premise.\n\nThis is a solid, honest status report, and the algorithmic details will be useful to anyone analyzing H.E.S.S. sample-mode data. For a journal submission, I would ask that the title and abstract match the demonstrated scope, and that the end-to-end optimization be completed before claiming sensitivity gains. As a proceedings, it deserves a serious referee and a conditional accept, with the wording softened to 'expected' where that is all the evidence supports.","headline":"Honest and useful technical write-up of H.E.S.S. sample-mode charge extraction; the simulated effective-area and Hillas-length results are solid, but the title overclaims — the sensitivity gain still depends on an analysis re-optimization that is explicitly underway.","tokens_in":6628,"tokens_out":2501,"would_cite":true,"duration_ms":27031,"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":"Reading full 1 GHz camera waveforms instead of a fixed 16 ns window improves H.E.S.S.'s detection sensitivity at low and high gamma-ray energies, by cutting night-sky noise and preventing truncation of long Cherenkov images.","keywords":["H.E.S.S.","imaging atmospheric Cherenkov telescope","waveform analysis","sample mode","charge extraction","effective area","gamma-ray astronomy","Cherenkov image truncation"],"falsifier":"Compare the retrained sample-mode analysis with charge mode on the existing Crab Nebula data: if the low-energy gamma-ray rate or effective area is not higher, or if high-impact-distance TeV images do not show longer Hillas lengths, the central sensitivity claim is contradicted.","tokens_in":5656,"feed_emoji":"🔭","tokens_out":11537,"duration_ms":101470,"temperature":0.7,"pith_summary":"The paper argues that switching H.E.S.S.'s upgraded cameras from a fixed 16 ns signal integration to a 9 ns integration placed around each pixel's signal peak improves gamma-ray detection in two ways: it admits less night-sky background, raising signal-to-noise at low energies, and it stops the clipping of Cherenkov images that last longer than 16 ns, exactly the situation for high-energy showers far from the telescope. Using simulated events, the paper shows longer recovered shower images and higher effective area at low energies when this sample mode is used. These gains matter because the affected events include the rare multi-TeV gamma rays that could reveal whether a source like Westerlund I is a PeVatron with a spectral cutoff. The paper expects additional high-energy gains once the analysis cuts and reconstruction templates are retrained for the new readout.","feed_headline":"Full waveform readout boosts H.E.S.S. sensitivity at both energy ends","feed_subtitle":"A 9 ns peak-window integration cuts night-sky noise and stops truncation of long TeV Cherenkov images.","key_machinery":"The mechanism is the parallel full-waveform readout of the upgraded H.E.S.S. I cameras, which stores up to 40 samples at 1 GHz per pixel alongside the old 16 ns integrated charge. The charge extraction that carries the argument is the next-neighbour peak-finding algorithm: for each pixel it sums the waveforms of adjacent pixels, takes the time of that sum's maximum as the pixel's peak time, and integrates the signal in a 9 ns window placed 3 ns before the peak, a quantity the paper calls SMMax9. This extraction feeds the same calibration, simulation, and analysis chains as before, so the readout and the integration window are the only new ingredients. The algorithm does two jobs at once: summing neighbours suppresses uncorrelated night-sky photons, and the 9 ns window keeps long Cherenkov pulses from being truncated.","core_discovery":"The central claim is that the new sample mode, in which full 1 GHz waveforms are stored for all pixels and charge is extracted by integrating 9 ns around a peak time found with a next-neighbour algorithm, captures the Cherenkov signal more faithfully than the legacy 16 ns window. In simulations, the recovered Hillas length, the length of the ellipse fitted to the shower image, is systematically larger in sample mode for high-impact-distance events, and the same waveform can look truncated in charge mode but complete in sample mode, as illustrated for a 223 TeV gamma ray at 925 m impact distance. Because the integration window is shorter, the noise contribution drops by a factor $\\sqrt{16/9}$, and the tail-cut thresholds can be lowered from 5/10 to 3/7 photoelectrons after accounting for the 0.91 gain ratio. With only an image-amplitude cut applied, the simulated effective area is higher in sample mode at low energies, and the paper argues that retraining the full analysis will extend the gain to high energies. These results are presented as performance expectations, since the full cut optimisation, boosted decision trees, and new ImPACT templates are still being produced.","pith_inferences":["If the retrained analysis preserves the simulated gains, the same peak-window waveform processing could be applied to future imaging atmospheric Cherenkov arrays, where full-waveform readout is already available.","The $\\sqrt{16/9}$ noise-reduction factor suggests a quantitative check: the low-energy effective-area gain should track the ratio of integrated noise, a prediction that can be tested on the Crab dataset once the final cuts are in place.","Going beyond the fixed 9 ns window, integrating each pixel's charge along the local time gradient of the image, which the paper names as motivation but does not implement, could push the sensitivity gain further by tracking the shower image as it sweeps across the camera."],"forward_implications":["Low-energy gamma-ray events should be detected at a higher rate because the shorter 9 ns window integrates less night-sky background than the old 16 ns window.","High-energy events with large impact distances should reconstruct with longer, less truncated shower images, improving direction and energy reconstruction.","Angular resolution is expected to improve for gamma rays above about 10 TeV at offset angles near $2^\\circ$, where sample-mode images can be roughly twice as long as charge-mode images.","Once boosted decision trees and ImPACT templates are retrained for sample mode, sensitivity gains are expected at the high-energy end as well, supporting searches for spectral cutoffs in PeVatron candidates such as Westerlund I.","Sample mode can become the default readout without giving up standard charge-mode data, because the two readouts run in parallel and remain backwards-compatible."],"supporting_citations":[{"why":"supplies the Crab Nebula as the standard gamma-ray source whose observations are used for technical verification of sample-mode data taking.","marker":"[1]"},{"why":"establishes the performance baseline of the pre-upgrade H.E.S.S. I cameras that the new readout must match or improve.","marker":"[2]"},{"why":"describes the electronics upgrade of the H.E.S.S. I cameras that makes the parallel full-waveform readout possible.","marker":"[3]"},{"why":"provides the Monte Carlo extensive-air-shower generator used to simulate the Cherenkov events in the performance studies.","marker":"[5]"},{"why":"provides the telescope simulation chain used to model camera response and produce the charge-mode versus sample-mode comparisons.","marker":"[6]"},{"why":"supplies the template-based reconstruction whose new sample-mode templates must be produced before the high-energy sensitivity gain can be realised.","marker":"[7]"}],"fun_headline_variants":["Waveform readout sharpens H.E.S.S gamma-ray view","H.E.S.S upgrade: full waveforms boost sensitivity","New H.E.S.S mode cuts noise, keeps long showers","Peak-window integration enhances H.E.S.S at all energies","H.E.S.S camera upgrade: sample mode wins at both ends"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The predicted sensitivity gain assumes the simulation chain faithfully models the upgraded cameras and that the analysis cuts, boosted decision trees, and ImPACT templates can all be retrained for sample mode without eroding the advantage seen with only a single image-amplitude cut.","fun_headline_variants_meta":{"raw":{"variants":["Waveform readout sharpens H.E.S.S gamma-ray view","H.E.S.S upgrade: full waveforms boost sensitivity","New H.E.S.S mode cuts noise, keeps long showers","Peak-window integration enhances H.E.S.S at all energies","H.E.S.S camera upgrade: sample mode wins at both ends"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000929,"raw_usage":{"total_tokens":4038,"prompt_tokens":1067,"completion_tokens":2971,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":683,"completion_tokens_details":{"reasoning_tokens":2884}},"tokens_in":683,"tokens_out":2971,"duration_ms":21462,"temperature":1.0,"reasoning_tokens":2884,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T13:36:14.439464+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Compare the retrained sample-mode analysis with charge mode on the existing Crab Nebula data: if the low-energy gamma-ray rate or effective area is not higher, or if high-impact-distance TeV images do not show longer Hillas lengths, the central sensitivity claim is contradicted.","supporting_citations":[{"cited_title":"Aharonian, et al., Observations of the Crab Nebula with H.E.S.S., A","cited_arxiv_id":null,"evidence_quote":"supplies the Crab Nebula as the standard gamma-ray source whose observations are used for technical verification of sample-mode data taking."},{"cited_title":"Vincent, et al., Performance of the H.E.S.S","cited_arxiv_id":null,"evidence_quote":"establishes the performance baseline of the pre-upgrade H.E.S.S. I cameras that the new readout must match or improve."},{"cited_title":"Giavitto, et al., The upgrade of the H.E.S.S","cited_arxiv_id":null,"evidence_quote":"describes the electronics upgrade of the H.E.S.S. I cameras that makes the parallel full-waveform readout possible."},{"cited_title":"Brun and F","cited_arxiv_id":null,"evidence_quote":"provides the Monte Carlo extensive-air-shower generator used to simulate the Cherenkov events in the performance studies."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"provides the telescope simulation chain used to model camera response and produce the charge-mode versus sample-mode comparisons."},{"cited_title":"Bernl\\\"ohr, Simulation of Imaging Atmospheric Cherenkov Telescopes with CORSIKA and sim\\_telarray, Astropart","cited_arxiv_id":null,"evidence_quote":"supplies the template-based reconstruction whose new sample-mode templates must be produced before the high-energy sensitivity gain can be realised."}],"review_version":1}