{"id":"4f9b94c8-457a-4529-8a84-9196eac3b928","arxiv_id":"2507.04324","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"Applying the ADF radio-amplitude model directly to voltage traces reconstructs inclined cosmic-ray directions to about 0.09 degrees and gives first-order energies, validated with simulations and GRANDProto300 candidates.","lead":"This paper shows that a radio pulse shape model built for electric fields can be applied directly to raw voltage traces from the GRANDProto300 prototype, giving shower directions accurate to about 0.09 degrees and a first-order energy estimate. The approach could simplify event selection and reconstruction for next-generation radio arrays hunting ultra-high-energy neutrinos.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The voltage-field proportionality asserted in §3.1 is the load-bearing bridge; flat gain alone does not guarantee it, and the claimed check is not shown—this needs a direct per-antenna ratio test.","rationale":"The reader's weakest assumption correctly identifies the voltage-electric-field linearity as the load-bearing bridge of the paper. Without it, the ADF model—originally derived for E-field amplitudes—cannot be applied to raw voltages, and the three headline results (event selection, 0.09° direction, energy proxy) all inherit a systematic error. The paper's flat-gain argument is plausible but incomplete: the ADF fit uses the Hilbert-envelope peak of the vector magnitude of three polarization channels, so the total power gain flatness over zenith is not sufficient to guarantee proportionality of the vector envelope peak. The antenna phase response, per-channel gains, and frequency-dependent filtering could all distort the envelope. The claimed simulation check is not presented numerically, and the subsequent validation (angular resolution, A/sin(α) correlation) uses the same simulated voltage chain, so it cannot independently demonstrate that the voltage envelope peak tracks the E-field envelope peak. The experimental cross-check between voltage and E-field energies (Fig. 5, top right) is a consistency check between two reconstructions that share the same ADF model and the same simulation-based calibration; it does not validate the proportionality against an external truth. A direct per-antenna ratio test in the simulation set is the most direct and least ambiguous way to settle whether the assumption holds; if it fails, the entire voltage-ADF approach would need an antenna-response correction or a different amplitude definition.","tokens_in":9022,"tokens_out":7729,"duration_ms":81622,"concrete_test":"From the 13,000 simulated events, compute for each triggered antenna the ratio R_i = V_peak_i / E_peak_i between the peak amplitude of the ADC voltage trace and the peak amplitude of the simulated E-field trace (before reconstruction). For each event, evaluate the scatter of R_i across the triggered array and its dependence on the antenna's angular coordinates (ω, η) in the shower plane and on the polarization channel. If the relative scatter of R_i exceeds the quoted 7.5% amplitude uncertainty (or if R_i shows a trend with ω or η), then the linear-scaling assumption is violated by a magnitude that would bias the ADF fit, and the 0.09° resolution and voltage-based energy proxy would need to be re-derived with an antenna-response correction. A null result—R_i constant within a few percent across all triggered events—would directly validate the assumption and settle the concern.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim depends on the proportionality between voltage and electric-field amplitudes asserted in §3.1. The paper's justification—flat antenna gain at 70–85° zenith—is insufficient because the ADF fit uses the peak of the Hilbert envelope of the vector sum of three polarization channels. A flat total gain does not guarantee that the per-channel amplitude and phase responses are identical across antennas or uniform with direction over the 50–200 MHz band; differences would distort the voltage envelope peak relative to the E-field envelope peak, biasing the ADF parameters (direction, A, δω) and hence the 0.09° median resolution and the A/sin(α) energy proxy. The claimed check ('comparing amplitudes of electric field traces with those of ADC traces') is not shown quantitatively in §3.2, so the proportionality is validated only indirectly: the similar angular resolution and energy correlation could arise even with a systematic voltage distortion if the same simulation chain is used to define both 'truth' and 'measurement'. No experimental ground truth is available for the 41 candidates, and the voltage-vs-E-field direction comparison is not shown.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript presents a reconstruction method for highly inclined cosmic-ray air showers detected by GRANDProto300 (GP300), based on fitting the phenomenological Angular Distribution Function (ADF) directly to raw voltage traces rather than to reconstructed electric fields. The pipeline combines a plane-wave timing fit, a spherical-wavefront emission-point fit, and an ADF amplitude-profile fit, followed by a voltage-based energy proxy A/sin(alpha). The method is validated on 13,000 simulated ZHAireS showers (0.1-3.98 EeV, 60-88 degrees zenith) with realistic electronics, noise, and timing jitter, yielding a median angular resolution of 0.09 degrees and a linear correlation between the corrected amplitude and electromagnetic energy. The approach is then applied to 41 cosmic-ray candidate events from GP300 commissioning data, with a cross-check between voltage-based and electric-field-based energy estimates showing about 32% relative spread. The paper concludes that the ADF method works directly on voltages, enabling event selection, direction reconstruction, and first-order energy estimation without antenna-response deconvolution.","tokens_in":9305,"tokens_out":3540,"duration_ms":42411,"significance":"If the voltage-based ADF approach is validated, it would be practically valuable for large sparse arrays like GRAND: it bypasses electric-field reconstruction, reduces processing complexity, and enables quick event identification and preliminary energy estimation. The simulation study is a clear strength: large statistics, realistic electronics and noise modeling, and a direct, machine-checked comparison against true shower directions. The reported 0.09-degree median angular resolution on simulated data is an explicit, falsifiable quantity. The experimental demonstration on 41 candidates, while preliminary, indicates the method works on real detector outputs. However, the central voltage-field proportionality assumption is only qualitatively motivated and the energy calibration is simulation-based and not independently anchored, so the quantitative claims (especially the energy proxy) are not yet fully established.","major_comments":[{"comment":"The load-bearing assumption that voltage traces scale approximately linearly with the electric field across the array is asserted but not quantitatively demonstrated. The text says this was 'checked with simulations presented in the following section, by comparing the amplitudes of electric field traces with those of ADC traces,' but Section 3.2 contains no such comparison figure, table, or numerical spread. A flat antenna gain at 70-85 degrees is not sufficient, because the ADF fit uses the peak of the Hilbert envelope of the vector sum of three polarization channels; flat total power gain does not guarantee uniform per-channel amplitude and phase response with direction or frequency over 50-200 MHz. Please add a direct per-antenna test on the simulated events: for each event, compute the ratio of the peak Hilbert-envelope amplitude of the ADC trace to that of the corresponding electric-field trace, and show its RMS variation across antennas, events, zenith angles, and frequency sub-bands. Without this, the median 0.09-degree resolution and the A/sin(alpha) energy proxy could be biased by an unmodeled voltage distortion, even if the simulation chain is internally consistent.","section":"Section 3.1, Eq. (1)"},{"comment":"The cross-check between voltage-based and electric-field-based energies is not an independent validation: both estimates use the same ADF model, the same simulation-derived correction factor f(rho, sin alpha), and the same underlying voltage traces through the same electronics model. The observed 32% relative spread therefore measures internal consistency, not absolute accuracy, and a common systematic bias would not appear in this comparison. Please state this explicitly and, if possible, validate the absolute energy scale with an external reference (e.g., a measured energy spectrum, coincidence with another detector, or a calibrated test source). The sentence in Section 4.4 noting that amplitude calibration has not yet been applied is important and should be moved to the main claims rather than only a closing caveat.","section":"Section 4.4, Figure 5 (Top Right)"},{"comment":"The event-selection claim is based on the fraction of events passing chi2_nu <= 25 in simulated cosmic rays (86%) versus random CD events (16%), but the 41 candidates were not drawn from a pure background sample: they were pre-selected by an independent analysis [10] whose criteria are not described here. The statement that the ADF fit 'refines the initial selection' is therefore not a controlled test of the ADF's background-rejection power. Please provide at least the selection criteria used in [10], or state explicitly that the 85% passing fraction is conditional on an already high-quality candidate set. A simple false-positive estimate for the combined cut would also strengthen the 'efficient event selection' claim.","section":"Sections 4.2-4.3"}],"minor_comments":[{"comment":"The abstract and introduction state that the method is 'applicable as well to upward-going trajectories,' but no upward-going showers are simulated, reconstructed, or tested in this work. This is an overclaim; either add a sentence explaining how the method extends trivially to upward-going geometries, or move this remark to the outlook section.","section":"Abstract and Section 1"},{"comment":"The choice of the chi2_nu <= 25 selection threshold is arbitrary and is justified only by the observed separation between signal and background. Please specify how this value was chosen (e.g., optimization on simulations or signal efficiency) and how the median angular resolution changes if the threshold is varied.","section":"Section 3.2.2"},{"comment":"The error bars on measured amplitudes are said to represent 'estimated 7.5% uncertainties,' but no derivation or reference for this value is given. Please state how the 7.5% was estimated (e.g., from noise covariance, calibration residuals, or simulation).","section":"Section 4.3 and Figure 2"},{"comment":"There are several typographical errors: 'istropic' should be 'isotropic' in Section 4.2; 'quiet distinct trends' should be 'quite distinct trends' in Section 4.2; 'Bij' and 'Ceopenhagen' appear in the author affiliations. A careful proofread is recommended.","section":"Throughout"},{"comment":"The caption states that the reconstructed footprint is 'derived from the Cherenkov angle (from the toy model), the core position, and the shower axis,' but the text does not define this toy model or how the footprint is drawn. Please add a brief definition or reference.","section":"Figure 3"},{"comment":"The statement that the reconstructed energy distribution spans 10^17 eV to 5x10^18 eV and 'matches expectations based on our exposure calculations' is not quantified; a plot of the reconstructed energy distribution compared with the expected distribution would be more convincing.","section":"Section 4.4"}],"recommendation":"major_revision","confidential_remarks":"This is a preliminary ICRC proceedings paper, so the bar for completeness is lower than a full journal article, but the central methodological claim--that the ADF can be applied directly to voltages--rests on a proportionality assumption that is not quantitatively demonstrated. The simulation validation is solid but self-contained; the experimental cross-check is not independent. I recommend major revision rather than rejection because the direction-reconstruction result is well supported by independent simulation, and the missing voltage-field comparison is straightforward to add with existing data. I also note that the paper's energy claims are explicitly preliminary, but the distinction between 'first-order estimator' and 'calibrated energy' should be made more prominent in the text."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a solid, practical methods paper for GRANDProto300, and the reader's CONDITIONAL verdict is the right one. The genuinely new thing is applying the ADF model directly to raw voltage traces, skipping electric-field deconvolution. The simulation work is the strongest part: 13,000 ZHAireS showers with realistic on-site noise and GPS jitter, median angular resolution 0.09 degrees, and a clean first-order correlation between the voltage-derived ADF amplitude and electromagnetic energy. The first 41 experimental candidates and the cross-check between voltage-based and E-field-based energies (32% relative spread) are useful initial evidence, and the paper is honest that amplitude calibration is not yet applied.\n\nThe soft spots are real but not fatal. The main one is the voltage-field proportionality asserted in Section 3.1. The flat gain argument is not enough to guarantee that per-channel amplitude and phase responses are uniform across antennas and over the 50-200 MHz band, since the ADF fit uses the Hilbert envelope of the vector sum of three channels. The paper says the proportionality was checked by comparing E-field and ADC amplitudes, but that comparison is not shown. A direct per-antenna ratio test, or at least a scatter plot of ADC vs E-field peak amplitudes across the triggered array, would settle it. The energy calibration is simulation-based, so the voltage vs E-field energy comparison in Section 4.4 is a consistency check between two uses of the same underlying model, not an independent validation. The experimental candidates have no external ground truth, so the real-data claims are demonstrations of self-consistency rather than proof. These are the normal limitations of a commissioning methods paper, and the authors do not overclaim.\n\nThe citation pattern looks fine: the ADF model is self-cited but it is their own prior work, and the direction-reconstruction claim is tested against independent simulation truth. The paper is well-scoped and the writing is clear.\n\nBottom line: this deserves a serious referee. The referee should ask for the voltage-E-field proportionality plot and a brief discussion of per-channel response variations. That is a revision, not a rejection. I would bring it to a reading group if anyone is working on radio arrays, and I would cite it if I were doing GRAND reconstruction.","headline":"A solid commissioning-stage methods paper: direct voltage-based ADF reconstruction is genuinely new and the simulation validation is strong, but the voltage-field proportionality is asserted rather than shown.","tokens_in":9787,"tokens_out":2223,"would_cite":true,"duration_ms":23929,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Fitting the ADF radio-emission model directly to raw antenna voltages—skipping electric-field reconstruction—recovers inclined cosmic-ray directions to a median 0.09 degrees and first-order energies.","keywords":["ultra-high-energy cosmic rays","radio detection","extensive air showers","angular distribution function","GRANDProto300","direction reconstruction","energy estimation","voltage traces"],"falsifier":"Take a set of triggered air-shower events with known simulated or well-reconstructed directions and compare the ADF fit on raw voltages with the fit on fully deconvolved electric fields; if the median direction difference grows well beyond 0.09 degrees, or if voltage-based energies scatter by much more than 32% against field-based energies, the linear voltage-to-field scaling is violated. A direct laboratory measurement of the 50–200 MHz gain spread across deployed GP300 antennas would also settle whether the antenna response is uniform enough.","tokens_in":8880,"feed_emoji":"📡","tokens_out":10220,"duration_ms":104196,"temperature":0.7,"pith_summary":"The paper claims that the Angular Distribution Function (ADF), a phenomenological model of radio emission from inclined air showers, can be fitted directly to the raw voltage traces recorded by GRANDProto300 antennas, without first reconstructing the electric field. On 13,000 simulated showers with zenith angles above 60 degrees, this voltage-level fit reaches a median angular resolution of 0.09 degrees and yields a scaling factor that tracks the shower's electromagnetic energy to first order. Applied to commissioning data, the same fit separates 41 cosmic-ray candidates from background and gives energy estimates that agree with electric-field-based estimates to within about 32%. If correct, the result means large radio arrays can do event selection, direction reconstruction, and first-order energy estimation straight from the detector's raw output.","feed_headline":"Voltage-only fits find cosmic-ray directions to 0.09 degrees","feed_subtitle":"GRANDProto300 skips electric-field deconvolution and fits raw antenna voltages to reconstruct inclined air showers.","key_machinery":"The central object is the Angular Distribution Function (ADF), a phenomenological model of the angular pattern of radio amplitudes in the 50–200 MHz band, parametrized by a global amplitude $A$, the shower direction $\\theta,\\phi$, and a profile width $\\delta\\omega$, evaluated at each antenna's angular coordinates $\\omega$ and $\\eta$ in the shower plane. It encodes the Cherenkov-ring enhancement through $\\tan\\omega/\\tan\\omega_c$, the geomagnetic asymmetry through $G_A \\cos\\eta/\\sin\\alpha$, and the early-late effect through the source distance $l$. The load-bearing step is fitting this model to raw voltage peaks rather than to deconvolved electric-field peaks, relying on the flat GRAND Horizon antenna gain over 70–85 degrees zenith to make voltages proportional to fields; the fitted $A$ then feeds the first-order energy estimator $E^*_{\\rm em}=A/[\\sin\\alpha \\, f(\\rho,\\sin\\alpha)]$, and the fit's $\\chi^2_\\nu$ acts as an event-selection and background-rejection statistic.","core_discovery":"The central claim is that the ADF—a model originally built for electric-field amplitudes—remains valid on raw voltages, so the electric-field reconstruction step can be bypassed. Because the GRAND Horizon antennas have a wide, flat gain for zenith angles between 70 and 85 degrees, the viewing angles across the array are nearly uniform, and the voltage recorded by each antenna is expected to scale approximately linearly with the electric field. With this assumption, the paper shows on simulations that the fitted amplitude parameter $A$, corrected as $A/\\sin(\\alpha)$, correlates linearly with the electromagnetic energy of the shower, and that the reconstructed directions have a median error of about 0.09 degrees. On the 41 experimental candidates, a reduced $\\chi^2_\\nu$ cut around 25 removes events with poor fits, the measured amplitudes show the predicted enhancement at the Cherenkov angle, and voltage-based energies agree with the deconvolved electric-field energies to about 32%. The authors note that amplitude calibration has not yet been applied, so the experimental results are preliminary.","pith_inferences":["Editorial extension: because the voltage fit skips deconvolution, it could plausibly run as an online or trigger-stage filter, reserving full electric-field reconstruction for candidate events.","Editorial extension: the paper shows the ADF and isotropic-background chi-squared distributions are separated but does not construct a joint cut; a two-dimensional selection could yield better background rejection than either cut alone.","Editorial extension: the linear-scaling argument is tuned to the GRAND Horizon antenna's flat 70–85 degree gain; whether similar voltage-level fitting works for other radio arrays with different antenna response is not established by this paper."],"forward_implications":["A reduced chi-squared cut at 25 applied to the voltage-based ADF fit selects cosmic-ray showers while rejecting about 84% of the random background events tested here.","For simulated showers at zenith angles above 60 degrees, the voltage-based reconstruction reaches a median angular resolution of about 0.09 degrees, matching electric-field-based fits.","The voltage-derived scaling factor $A/\\sin(\\alpha)$ correlates linearly with electromagnetic energy to first order, and voltage-based energies agree with electric-field-based energies to within about 32%.","A combined cut on the ADF fit and a simple isotropic-emission fit should give stronger background rejection once the detector reaches its full configuration.","The same approach extends to upward-going trajectories, the geometry relevant for Earth-skimming neutrino searches at full GRAND scale."],"supporting_citations":[{"why":"Defines the ADF model and the three-step reconstruction pipeline that this work adapts to voltage traces.","marker":"[2]"},{"why":"Supplies the spherical wavefront and emission-point model for very inclined showers used in step 2.","marker":"[5]"},{"why":"Documents the GRAND Horizon antenna whose flat 70–85 degree gain motivates treating voltages as proportional to fields.","marker":"[7]"},{"why":"Provides the modeled electronics chain that converts simulated electric fields into realistic voltage signals.","marker":"[8]"},{"why":"Source of the 41 GP300 cosmic-ray candidate events reconstructed in Section 4.","marker":"[10]"},{"why":"Deconvolution procedure used to reconstruct electric fields for the energy cross-check.","marker":"[14]"},{"why":"Underlies the coherence correction factor used in the electromagnetic energy estimator.","marker":"[6]"}],"fun_headline_variants":["Voltage-only fits yield 0.09° cosmic-ray direction accuracy","GRANDProto300 skips E-field step, fits voltages for direction","Raw voltage fits give precise cosmic-ray directions, energy","Voltage-based CR reconstruction: 0.09° median error","GRANDProto300 validates voltage-only reconstruction on first candidates"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The method depends on the premise that each antenna's raw voltage tracks the radio field essentially linearly, with antenna response varying little across the array; this was inferred from the antenna's flat gain and checked only through simulations, not with a dedicated measurement.","fun_headline_variants_meta":{"raw":{"variants":["Voltage-only fits yield 0.09° cosmic-ray direction accuracy","GRANDProto300 skips E-field step, fits voltages for direction","Raw voltage fits give precise cosmic-ray directions, energy","Voltage-based CR reconstruction: 0.09° median error","GRANDProto300 validates voltage-only reconstruction on first candidates"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.00054,"raw_usage":{"total_tokens":2616,"prompt_tokens":997,"completion_tokens":1619,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":613,"completion_tokens_details":{"reasoning_tokens":1531}},"tokens_in":613,"tokens_out":1619,"duration_ms":13321,"temperature":1.0,"reasoning_tokens":1531,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-06T19:50:15.166303+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Take a set of triggered air-shower events with known simulated or well-reconstructed directions and compare the ADF fit on raw voltages with the fit on fully deconvolved electric fields; if the median direction difference grows well beyond 0.09 degrees, or if voltage-based energies scatter by much more than 32% against field-based energies, the linear voltage-to-field scaling is violated. A direct laboratory measurement of the 50–200 MHz gain spread across deployed GP300 antennas would also settle whether the antenna response is uniform enough.","supporting_citations":[{"cited_title":"Guelfandet al","cited_arxiv_id":null,"evidence_quote":"Defines the ADF model and the three-step reconstruction pipeline that this work adapts to voltage traces."},{"cited_title":"Decoeneet al","cited_arxiv_id":null,"evidence_quote":"Supplies the spherical wavefront and emission-point model for very inclined showers used in step 2."},{"cited_title":"Álvarez-Muñiz et al.)Sci","cited_arxiv_id":null,"evidence_quote":"Documents the GRAND Horizon antenna whose flat 70–85 degree gain motivates treating voltages as proportional to fields."},{"cited_title":"Alves Batista et al.)Comput","cited_arxiv_id":null,"evidence_quote":"Provides the modeled electronics chain that converts simulated electric fields into realistic voltage signals."},{"cited_title":"Lavoisieret al.inPoS(ICRC2025)314","cited_arxiv_id":null,"evidence_quote":"Source of the 41 GP300 cosmic-ray candidate events reconstructed in Section 4."},{"cited_title":"Chicheet al","cited_arxiv_id":null,"evidence_quote":"Underlies the coherence correction factor used in the electromagnetic energy estimator."}],"review_version":1}