{"id":"7f0b15a0-2eb8-470a-868e-3e59c45d5c8b","arxiv_id":"2507.07260","paper_version":1,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"The GRAND prototypes, with 79 combined detection units, are operating and have recorded candidate cosmic-ray events, marking progress toward a 200,000 km² ultra-high-energy neutrino observatory.","lead":"GRAND, a proposed giant radio array for detecting ultra-high-energy neutrinos, reports that its three prototype arrays are operational and have already detected cosmic-ray events. The collaboration is using these prototypes to validate the technology before deploying GRAND10k, a two-hemisphere array of 20,000 antennas.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Stand-alone detection claim rests on an unvalidated candidate sample; no false-positive rate or multi-event external cross-check is presented.","rationale":"I read in good faith. The paper is a transparent status report, and the hardware and commissioning results (noise homogeneity, Galactic modulation, Wi-Fi throughput, timing resolution, beacon trigger test) are credible and independently checkable. The reader's ACCEPT is reasonable for a proceedings. However, the strongest claim singled out by the reader, the first stand-alone radio detection, is exactly where the evidence is thinnest: an unvalidated candidate list. The internal count inconsistency and absence of a false-positive analysis make this a correctness risk in the central claim, not merely an external-consensus disagreement. The proposed blind cross-check on G@A would settle it. This is not grounds for rejection, but it warrants conditional acceptance with wording or evidence revision.","tokens_in":9440,"tokens_out":7269,"duration_ms":86953,"concrete_test":"Using the G@A dataset over a fixed period (e.g., three months of 2025), apply the GP300 candidate identification pipeline [16] to all G@A self-triggered events while blinded to Auger's reconstructed event list; after unblinding, compute the fraction of pipeline-selected events with an Auger air shower in the expected direction/time window, with an explicit estimate of accidental coincidences from time-offset trials. A high matched fraction (e.g., >90% for high-quality events) would validate the stand-alone detection claim; a low fraction would show that the 41 GP300 events are unvalidated candidates and the conclusion should be reworded accordingly.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The conclusion (Sec. 7) states that 'our first stand-alone radio detection of cosmic-ray events was achieved.' The only evidence for GP300 is 41 'candidates' (Sec. 5.2), selected by a pipeline explicitly described as still being optimized [16], with no reported false-positive or background-rejection rate. The 75% trigger efficiency was measured with a beacon generator, not with air-shower signals. The sample is also internally inconsistent: 41 candidates, 29 with valid energy reconstruction, and Fig. 5 shows 26 events, with no single cut chain explaining the reductions. The sole independent cross-check is one G@A event coincident with a 1.3e19 eV Auger cosmic ray (Sec. 5.3); a single coincidence validates radio emission from a known CR but does not validate stand-alone selection at GP300, where no particle detector provides ground truth. Since the paper's central claim is that the detection principle is being validated, the categorical 'first stand-alone radio detection' wording goes beyond what the presented, explicitly preliminary evidence establishes. The science case for the neutrino channel is a separate, clearly stated model-dependent extrapolation.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This ICRC 2025 proceedings paper reports the current status of the GRAND prototype phase. The three prototypes (GRANDProto300 with 65 deployed units, GRAND@Auger with 10 units, and a 4-unit test setup at Nançay) are described in terms of hardware, trigger and DAQ performance, commissioning results, and first cosmic-ray candidate events. The paper also summarizes the GRAND science case, the detection principle, the simulation/reconstruction framework, and the roadmap toward the GRAND10k phase. The stated highlight is the first stand-alone radio detection of cosmic-ray events during commissioning, presented as a step toward validating the GRAND detection principle.","tokens_in":9597,"tokens_out":4009,"duration_ms":42389,"significance":"If the candidate events are confirmed, this paper demonstrates that a sparse self-triggered radio array can identify ultra-high-energy air showers without an external particle-detector trigger, which is the core technological premise of the planned GRAND10k array. The reported hardware performance, such as the sub-5 ns timing resolution, the stable low-noise operation, and the success in reproducing the Galactic-plane sky-noise modulation without adjustable parameters (Fig. 3), is a solid technical achievement. The paper is appropriately transparent that calibration, selection, and energy reconstruction are still being refined, and it openly defers quantitative background-rejection and efficiency measurements to future work. The main limitation is that the small candidate sample and the lack of a demonstrated false-positive rejection rate mean the claim of “stand-alone detection” should be framed as a preliminary candidate-level result rather than a validated detection.","major_comments":[{"comment":"Section 7 states “Our first stand-alone radio detection of cosmic-ray events was achieved,” but Section 5.2 consistently describes the events as “candidates” selected by a procedure that is “still being optimized,” and no false-positive or background-rejection rate is reported anywhere in the paper. The G@A event coincident with a 1.3×10^19 eV Auger cosmic ray (Section 5.3) corroborates that the radio signal from a known cosmic ray can be observed, but it does not demonstrate that the GP300 stand-alone selection rejects backgrounds. The conclusion should be reworded to “candidate cosmic-ray events” and should explicitly note that validation of the stand-alone detection principle requires the background-rejection and efficiency quantification planned for the near future (Section 6).","section":"Section 5.2 and Fig. 5"}],"minor_comments":[{"comment":"There is a typo: “pimarily” should be “primarily”.","section":"Introduction"},{"comment":"The phrase “three independant methods” should be “three independent methods”.","section":"Section 5.2"},{"comment":"The word “modilation” should be “modulation”.","section":"Section 5.3"},{"comment":"The sentence “trigger efficiency of ∼75% for event rates up to 50 Hz” should specify that this was measured with a beacon generator and applies to the first-level trigger response to test pulses, not to the full air-shower selection efficiency, which also depends on the offline identification pipeline.","section":"Section 5.2, trigger efficiency"},{"comment":"The notation “24μс” in the caption should use a standard unit format, e.g., “24 μs.”","section":"Fig. 3 caption"}],"recommendation":"minor_revision","confidential_remarks":"This is a conference proceedings status report, so the bar for technical completeness should be matched to that genre. The central claim is a milestone claim about first candidates, and the paper itself already includes caveats in the figure captions and Section 6. The requested changes (clarifying the event-number progression and tempering the conclusion) are local and do not affect the substantive technical content. I see no grounds for rejection, and the issues do not require a full major revision."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a solid, pleasantly candid status report from GRAND. The real news is straightforward: GP300 now runs 65 antennas, G@A has 10 on the Auger site, and both see Galactic noise modulation and cosmic-ray-like transients; one G@A event lines up with a 1.3e19 eV Auger shower. The paper also shows trigger efficiency measurements and a convincing simulation-vs-data noise comparison, and it points to the open-source GRANDlib. For anyone tracking radio detection of UHE air showers, that is genuinely useful.\n\nThe paper does well by flagging its own limitations: calibration and candidate selection are repeatedly called preliminary, and the analyses live in companion ICRC papers. That is the right way to write a proceedings status report.\n\nThe soft spot is the conclusion. 'Our first stand-alone radio detection of cosmic-ray events was achieved' is stronger than the evidence presented. The GP300 sample is 41 candidates from a still-optimized pipeline, with no false-positive or background-rejection rate reported, and the trigger efficiency was measured with a beacon generator rather than real air showers. The numbers also don't quite line up (41 candidates, 29 with valid energy, 26 in Fig. 5) without a cut chain in the text. The single Auger coincidence is a nice cross-check but only for one event and at a different site. None of this sinks the status report, because the paper itself labels everything preliminary; it just means the conclusion overstates where the analysis currently stands. The neutrino sensitivity projections remain model-dependent, but that's clearly stated and is a science case, not a flaw.\n\nThis paper is for the UHE astroparticle community as a progress snapshot. It deserves a serious referee, mainly because the technical milestones matter and the collaboration has been transparent. For peer review I'd recommend accept after the authors soften the 'first stand-alone detection' wording and add one sentence on the validation status of the candidate sample. It is a proceedings paper, not a discovery claim, and should be read as such.","headline":"GRAND's prototypes are clearly working and the paper is an honest status update, but the 'first stand-alone detection' claim runs ahead of the unvalidated candidate sample.","tokens_in":10148,"tokens_out":2157,"would_cite":true,"duration_ms":23653,"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":"GRAND, a proposed ultra-high-energy neutrino observatory made of self-triggered radio antennas, reports that its prototype arrays have detected cosmic-ray air showers in stand-alone mode during commissioning, validating the detection…","keywords":["ultra-high-energy neutrinos","radio detection of air showers","self-triggered antenna array","GRANDProto300","cosmogenic neutrinos","GRAND10k","extensive air showers"],"falsifier":"If the 41 GRANDProto300 cosmic-ray candidates mostly turn out to be radio-frequency interference, or if the GRAND@Auger event coincident with the Auger cosmic ray is not followed by more coincidences once both arrays run stably, then the claim that GRAND can detect air showers in stand-alone mode is not supported. A concrete check would be to run the candidate-identification pipeline against independently reconstructed shower properties and compare the measured coincidence rate with Auger to the predicted rate.","tokens_in":9217,"feed_emoji":"📡","tokens_out":5149,"duration_ms":52696,"temperature":0.7,"pith_summary":"This status report argues that the GRAND detection principle is being validated. Three prototype arrays are running: 65 units at GRANDProto300 in the Gobi Desert, 10 at GRAND@Auger in Argentina, and 4 test units at Nançay. During commissioning, GRANDProto300 identified 41 cosmic-ray candidates with reconstructed directions and energies, and GRAND@Auger recorded a radio event coincident with a 1.3×$10^{19}$ eV cosmic ray seen by the Auger array. A sympathetic reader would take this as the first stand-alone radio detection of air showers by the GRAND systems, meaning the self-triggered antenna technology works, and as evidence that the larger GRAND10k array can be deployed. The paper's deeper aim is to show the path to detecting ultra-high-energy neutrinos via Earth-skimming tau neutrinos.","feed_headline":"GRAND radio prototypes detect first cosmic-ray showers","feed_subtitle":"Stand-alone antennas at two sites catch air showers, validating the trigger design for a 20,000-antenna neutrino hunter.","key_machinery":"The central mechanism is self-triggered radio detection of extensive air showers: cosmic-ray or neutrino-induced showers produce coherent geomagnetic radio emission in the tens-of-MHz range, and each GRAND detection unit's three orthogonal radiators (east–west, north–south, vertical), sensitive over 30–200 MHz, capture this transient pulse. A front-end board filters 50–200 MHz, digitizes with a 14-bit 500 MSamples/s ADC, and an FPGA runs a first-level trigger; when three to five units register within a causal time window, a second-level trigger records 2 µs waveforms. The prototypes show that this chain works stand-alone, with roughly 75% trigger efficiency at rates up to 50 Hz, better than 5 ns relative timing, and noise levels matching the expected Galactic radio sky.","core_discovery":"GRAND claims to have achieved its first stand-alone radio detection of cosmic-ray events during the commissioning of its prototypes. GRANDProto300, with 65 detection units running since the end of 2024, produced a list of 41 cosmic-ray candidates between December 2024 and March 2025; for 26 of them with at least five triggered units, three independent methods—a lateral distribution function fit, an angular distribution function fit, and a graph neural network—yielded consistent energies, with claimed resolutions better than 0.1° in arrival direction and 15% in energy. GRAND@Auger, 10 units deployed on the Pierre Auger site, detected a radio event coincident with a 1.3×$10^{19}$ eV cosmic ray observed by Auger. These results are presented as validation of the GRAND detection principle: self-triggered radio detection of extensive air showers, in preparation for GRAND10k.","pith_inferences":["The paper reports 'candidates,' not a fully published event sample; whether these survive complete background rejection will decide how firmly the claimed validation holds.","If the cosmic-ray detection rate reaches the expected tens per day, the array could act as a cosmic-ray observatory on its own, producing spectra in the 10^17–10^18 eV range even before any neutrinos are seen.","The same trigger and reconstruction chain could significantly lower the energy threshold if the planned advanced triggers and hybrid phased-array designs are adopted, potentially reducing the number of antennas needed to meet the science goals.","The neutrino-specific detection channel remains untested; a decisive test would require a near-horizontal Earth-skimming tau-neutrino candidate or a limit that rules out the predicted cosmogenic flux."],"forward_implications":["The self-triggered, stand-alone detection mode is validated, so the staged plan to complete GRANDProto300 (289 units, 200 km²) and then deploy GRAND10k from 2030 is technically grounded.","A 20,000-antenna array covering both hemispheres would have about 20 times the collecting area of the Pierre Auger Observatory, enabling ultra-high-energy cosmic-ray studies and searches for transient point sources at roughly 0.1° resolution.","GRAND's sensitivity would reach the cosmogenic neutrino flux predicted by current models, opening a detection window above roughly 100 PeV that IceCube and KM3NeT cannot cover.","The same antenna network can serve as a wide-field instrument for fast radio bursts, solar flares, and lightning studies, as already illustrated by solar-flare observations in GRANDProto300.","The reconstruction chain, integrating deconvolution, cosmic-ray identification, and energy estimators, is ready for stable operation once the prototypes reach their nominal candidate rates."],"supporting_citations":[{"why":"Defines the GRAND design, the Earth-skimming tau-neutrino detection principle, and the end-to-end simulation used for effective-area calculations.","marker":"[3]"},{"why":"Supplies the cosmogenic neutrino flux models that set the sensitivity target GRAND is designed to reach.","marker":"[4]"},{"why":"Demonstrates that antenna arrays can detect air showers in stand-alone mode, providing the precedent GRAND's approach extends.","marker":"[13]"},{"why":"Documents GRANDProto300 commissioning, including noise reduction and the observed daily Galactic modulation.","marker":"[9]"},{"why":"Reports the GRAND@Auger setup and the radio event observed in coincidence with a cosmic ray detected by Auger.","marker":"[21]"},{"why":"Defines the cosmic-ray identification procedure used to produce the list of 41 candidates.","marker":"[16]"},{"why":"Provides the lateral distribution function fit used for energy reconstruction of the candidates.","marker":"[17]"},{"why":"Provides the angular distribution function fit used as an independent reconstruction method.","marker":"[18]"},{"why":"Provides the graph neural network energy reconstruction used as the third independent method.","marker":"[19]"}],"fun_headline_variants":["GRAND prototypes catch first cosmic rays","First air showers seen by GRAND radio prototypes","GRAND prototype arrays validate self-triggered detection","GRAND's first steps to a 20,000-antenna neutrino hunter"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The neutrino science case assumes that the cosmogenic neutrino flux at ultra-high energies is high enough for the planned sensitivity to detect it, and that tau leptons produced by Earth-skimming neutrinos will emerge into the atmosphere and generate detectable radio-emitting air showers; the prototype results validate cosmic-ray air-shower detection, not yet that neutrino channel.","fun_headline_variants_meta":{"raw":{"variants":["GRAND prototypes catch first cosmic rays","First air showers seen by GRAND radio prototypes","GRAND prototype arrays validate self-triggered detection","GRAND's first steps to a 20,000-antenna neutrino hunter"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000188,"raw_usage":{"total_tokens":1343,"prompt_tokens":969,"completion_tokens":374,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":585,"completion_tokens_details":{"reasoning_tokens":308}},"tokens_in":585,"tokens_out":374,"duration_ms":4731,"temperature":1.0,"reasoning_tokens":308,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T18:45:01.984990+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"If the 41 GRANDProto300 cosmic-ray candidates mostly turn out to be radio-frequency interference, or if the GRAND@Auger event coincident with the Auger cosmic ray is not followed by more coincidences once both arrays run stably, then the claim that GRAND can detect air showers in stand-alone mode is not supported. A concrete check would be to run the candidate-identification pipeline against independently reconstructed shower properties and compare the measured coincidence rate with Auger to the predicted rate.","supporting_citations":[{"cited_title":"Álvarez-Muñizet al","cited_arxiv_id":null,"evidence_quote":"Defines the GRAND design, the Earth-skimming tau-neutrino detection principle, and the end-to-end simulation used for effective-area calculations."},{"cited_title":"Alves Batista, R","cited_arxiv_id":null,"evidence_quote":"Supplies the cosmogenic neutrino flux models that set the sensitivity target GRAND is designed to reach."},{"cited_title":"Charrieret al","cited_arxiv_id":null,"evidence_quote":"Demonstrates that antenna arrays can detect air showers in stand-alone mode, providing the precedent GRAND's approach extends."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Documents GRANDProto300 commissioning, including noise reduction and the observed daily Galactic modulation."},{"cited_title":"Torres de Mello NetoPoS ICRC2025(2025) 1024","cited_arxiv_id":null,"evidence_quote":"Reports the GRAND@Auger setup and the radio event observed in coincidence with a cosmic ray detected by Auger."},{"cited_title":"LavoisierPoS ICRC2025(2025) 314","cited_arxiv_id":null,"evidence_quote":"Defines the cosmic-ray identification procedure used to produce the list of 41 candidates."},{"cited_title":"Gulzow and T","cited_arxiv_id":null,"evidence_quote":"Provides the lateral distribution function fit used for energy reconstruction of the candidates."},{"cited_title":"Guelfandet al","cited_arxiv_id":null,"evidence_quote":"Provides the angular distribution function fit used as an independent reconstruction method."},{"cited_title":"Ferrière and A","cited_arxiv_id":null,"evidence_quote":"Provides the graph neural network energy reconstruction used as the third independent method."}],"review_version":1}