arxiv: 2605.12769 · v1 · submitted 2026-05-12 · ✦ hep-ex

Recognition: unknown

First evidence of neutrino absorption on argon using ⁸B solar neutrinos in DEAP-3600

P. Adhikari , P.-A. Amaudruz , D. J. Auty , M. Batygov , B. Beltran , M. A. Bigentini , C. E. Bina , W. Bonivento

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M. G. Boulay J. Brachman B. Broerman J. F. Bueno M. Cadeddu B. Cai M. C\`ardenas-Montes N. Cargioli S. Cavuoti S. Choudhary B. T. Cleveland R. Crampton S. Daugherty P. Di Stefano G. Dolganov L. Doria F. A. Duncan M. Dunford E. Ellingwood A. Erlandson S. S. Farahani N. Fatemighomi L. Ferro G. Fiorillo R. J. Ford A. Garai P. Garc\'ia Abia S. Garg P. Giampa D. Goeldi P. Gorel K. Graham A. L. Hallin M. Hamstra S. Haskins T. Hoyte J. Hu J. Hucker D. Huff T. Hugues A. Ilyasov B. Jigmeddorj C. J. Jillings G. Kaur A. Kemp M. Khoshraftar Yazdi G. Killaire M. Ku\'zniak F. La Zia M. Lai S. Langrock B. Lehnert M. Lissia L. Luzzi I. Machulin A. Maru J. Mason A. B. McDonald T. McElroy J. B. McLaughlin C. Mielnichuk L. Mirasola S. Mohanty A. Moharana J. Monroe A. Murray M. Needs C. Ng G. Nieradka G. Olivi\'ero M. Olszewski S. Pal D. Papi B. Park R. Pavarani M. Perry V. Pesudo T. R. Pollmann F. Rad C. Rethmeier F. Reti\`ere L. Roszkowski R. Santorelli F. G. Schuckman II M. Sestu S. Seth V. Shalamova P. Skensved T. Smirnova K. Sobotkiewich T. Sonley J. Sosiak J. Soukup R. Stainforth M. Stringer J. Tang P. Taylor C. Tierney S. Tullio R. Turcotte-Tardif E. V\'azquez-J\'auregui G. Vera D\'iaz S. Viel B. Vyas J. Walding M. Ward S. Westerdale R. Wormington

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Pith reviewed 2026-05-14 19:41 UTC · model grok-4.3

classification ✦ hep-ex

keywords neutrino absorptionargonsolar neutrinoscharged current interaction8B neutrinoscross section measurementDEAP-3600

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The pith

DEAP-3600 provides first evidence of 8B solar neutrino absorption on argon nuclei.

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

The paper reports the first observation of electron neutrinos from the sun being absorbed by argon atoms through charged-current interactions. Using data from the DEAP-3600 detector with an exposure of about 7.3 tonne-years, they identified six events in a specific energy range that match the expected signal from 8B neutrinos after accounting for detector effects. This observation reaches 4 sigma significance above background and yields a measured cross section that is higher than theoretical predictions. Such a result is important because it validates the use of argon as a target for solar neutrino studies and provides data to test models of neutrino-nucleus interactions at low energies.

Core claim

We report experimental evidence for electron neutrino charged-current interactions (neutrino absorption, CC νe) from 8B solar neutrinos on 40Ar using an exposure of (7.29 ± 0.05) tonne·years in the DEAP-3600 detector. A region of interest (ROI) of 10.5-13.0 MeV reconstructed energy is used. We observe 5 single-peak and 1 double-peak neutrino-like events consistent with the 8B solar neutrino energy spectrum in the ROI after correcting for nonlinearities in the detector response at high energies. With an expected background of 0.48 events, the data correspond to a significance of 4.0σ. We report an energy-averaged cross section of (4.0 +2.0-1.6 stat +0.8-0.7 sys)×10−41 cm2 in the ROI, a factor

What carries the argument

The identification of single-peak and double-peak events in the liquid argon detector after applying nonlinearity corrections to the energy reconstruction, allowing distinction of neutrino absorption signals from background in the 10.5-13 MeV range.

If this is right

Future solar neutrino experiments using liquid argon can expect to detect these interactions with higher statistics.
The measured cross section provides a benchmark for improving theoretical calculations of charged-current neutrino interactions on argon.
This technique demonstrates background suppression sufficient for observing rare high-energy solar neutrino events in underground detectors.
It supports the development of argon-based detectors for both solar and supernova neutrino detection.

Where Pith is reading between the lines

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

A higher-than-predicted cross section may indicate the need for updated nuclear models or could point to contributions from other processes not included in the 2009 calculation.
This result could be combined with other neutrino experiments to refine the understanding of solar neutrino fluxes and oscillations at these energies.
Larger exposures in similar detectors could turn this into a precision measurement rather than evidence.
The method of using solar neutrinos as a calibration source for argon detectors may apply to other targets in future experiments.

Load-bearing premise

The six observed events are produced by neutrino absorption on argon rather than unmodeled backgrounds or detector artifacts after the high-energy nonlinearity corrections.

What would settle it

A dedicated follow-up measurement with greater exposure that finds the number of events consistent with the lower predicted cross section instead of the observed higher value would falsify the claim of a significantly elevated cross section.

Figures

Figures reproduced from arXiv: 2605.12769 by A. B. McDonald, A. Erlandson, A. Garai, A. Ilyasov, A. Kemp, A. L. Hallin, A. Maru, A. Moharana, A. Murray, B. Beltran, B. Broerman, B. Cai, B. Jigmeddorj, B. Lehnert, B. Park, B. T. Cleveland, B. Vyas, C. E. Bina, C. J. Jillings, C. Mielnichuk, C. Ng, C. Rethmeier, C. Tierney, D. Goeldi, D. Huff, D. J. Auty, D. Papi, E. Ellingwood, E. V\'azquez-J\'auregui, F. A. Duncan, F. G. Schuckman II, F. La Zia, F. Rad, F. Reti\`ere, G. Dolganov, G. Fiorillo, G. Kaur, G. Killaire, G. Nieradka, G. Olivi\'ero, G. Vera D\'iaz, I. Machulin, J. B. McLaughlin, J. Brachman, J. F. Bueno, J. Hu, J. Hucker, J. Mason, J. Monroe, J. Sosiak, J. Soukup, J. Tang, J. Walding, K. Graham, K. Sobotkiewich, L. Doria, L. Ferro, L. Luzzi, L. Mirasola, L. Roszkowski, M. A. Bigentini, M. Batygov, M. Cadeddu, M. C\`ardenas-Montes, M. Dunford, M. G. Boulay, M. Hamstra, M. Khoshraftar Yazdi, M. Ku\'zniak, M. Lai, M. Lissia, M. Needs, M. Olszewski, M. Perry, M. Sestu, M. Stringer, M. Ward, N. Cargioli, N. Fatemighomi, P.-A. Amaudruz, P. Adhikari, P. Di Stefano, P. Garc\'ia Abia, P. Giampa, P. Gorel, P. Skensved, P. Taylor, R. Crampton, R. J. Ford, R. Pavarani, R. Santorelli, R. Stainforth, R. Turcotte-Tardif, R. Wormington, S. Cavuoti, S. Choudhary, S. Daugherty, S. Garg, S. Haskins, S. Langrock, S. Mohanty, S. Pal, S. Seth, S. S. Farahani, S. Tullio, S. Viel, S. Westerdale, T. Hoyte, T. Hugues, T. McElroy, T. R. Pollmann, T. Smirnova, T. Sonley, V. Pesudo, V. Shalamova, W. Bonivento.

**Figure 2.** Figure 2: FIG. 2. Energy-averaged cross section result, compared with [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3. Energy-averaged cross section measurement result [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗

read the original abstract

We report experimental evidence for electron neutrino charged-current interactions (neutrino absorption, CC $\nu_e$) from $^{8}$B solar neutrinos on $^{40}$Ar using an exposure of ($7.29 \pm 0.05$) tonne$\cdot$years in the DEAP-3600 detector. A region of interest (ROI) of 10.5-13.0 MeV reconstructed energy calibrated on single-peak events, corresponding to incident neutrino energy in 12.0-14.5 MeV, is used for this measurement. We observe 5 single-peak and 1 double-peak neutrino-like events consistent with the $^{8}$B solar neutrino energy spectrum in the ROI after correcting for nonlinearities in the detector response at high energies. With an expected background of $0.48~^{+0.16}_{-0.15}$ events, the data correspond to a significance of $4.0\,\sigma$ with respect to the background-only hypothesis. We report an energy-averaged cross section of $(4.0~^{+2.0}_{-1.6}~\mathrm{(stat)}~^{+0.8}_{-0.7}~\mathrm{(sys)})\times 10^{-41}\,\mathrm{cm}^2$ in the ROI for the CC $\nu_{e}$ signal, a factor $(2.4~^{+1.3}_{-1.0})$ higher than predicted by Bhattacharya, Goodman and Garc\'ia (2009).

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.

Desk Editor's Note private letter to a colleague

DEAP-3600 claims the first 4-sigma evidence for 8B solar neutrino absorption on argon, but the result sits on a narrow ROI whose background model after nonlinearity corrections is the main point that needs checking.

read the letter

The paper's core claim is straightforward: with 7.29 tonne-years they see 6 events (5 single-peak, 1 double-peak) in the 10.5-13 MeV window against 0.48 expected background, giving 4 sigma and an energy-averaged cross section of (4.0 +2.0-1.6 stat +0.8-0.7 sys) x 10^-41 cm^2, roughly 2.4 times the Bhattacharya-Goodman-Garcia prediction. That is new; no earlier measurement of this specific CC channel with solar neutrinos is cited, so it supplies the first experimental anchor point at these energies for argon response calculations and for future LAr detectors.

Referee Report

2 major / 1 minor

Summary. The manuscript reports the first experimental evidence for charged-current neutrino absorption (CC ν_e) on 40Ar using 8B solar neutrinos in the DEAP-3600 liquid argon detector. With an exposure of 7.29 tonne-years, six neutrino-like events (5 single-peak, 1 double-peak) are observed in the 10.5-13.0 MeV reconstructed-energy ROI (corresponding to 12.0-14.5 MeV incident neutrinos) after nonlinearity corrections. Subtracting an estimated background of 0.48^{+0.16}_{-0.15} events yields a 4.0σ excess over background-only, from which an energy-averaged cross section of (4.0^{+2.0}_{-1.6} stat ^{+0.8}_{-0.7} sys) × 10^{-41} cm² is extracted, a factor 2.4^{+1.3}_{-1.0} above the Bhattacharya et al. (2009) prediction.

Significance. If the background model and event classification hold, the result would constitute the first direct observation of this interaction channel, providing a new calibration point for argon-based neutrino detectors and a test of solar-neutrino flux and cross-section calculations. The large statistical and systematic uncertainties, however, limit its immediate impact on theory or detector design until the background extrapolation is independently validated.

major comments (2)

[ROI definition and background model (abstract and results)] The 4.0σ significance and extracted cross section rest entirely on the background estimate of 0.48^{+0.16}_{-0.15} events in the narrow 10.5-13 MeV ROI. The manuscript provides no quantitative sideband measurement, Monte Carlo validation, or calibration data demonstrating that the high-energy nonlinearity correction leaves a residual background rate this low; an unmodeled component at the level of ~1 event would reduce the excess below 3σ. This assumption is load-bearing for the central claim.
[Cross-section extraction and comparison to theory] The reported factor 2.4^{+1.3}_{-1.0} discrepancy with the Bhattacharya et al. (2009) prediction is presented without a dedicated discussion of possible residual systematics in the energy-scale correction or event-selection efficiency at 10-13 MeV. Because the central value carries large asymmetric errors and the measurement is a single-ROI counting experiment, the discrepancy cannot yet be interpreted as a robust tension with theory.

minor comments (1)

[Event classification] The abstract states the six events are 'consistent with the 8B solar neutrino energy spectrum' but does not quantify the spectral shape test or the efficiency of the single-peak versus double-peak classification; a brief supplemental figure or table would improve clarity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful and constructive review. We address the two major comments point by point below, indicating the revisions we will make to strengthen the manuscript.

read point-by-point responses

Referee: [ROI definition and background model (abstract and results)] The 4.0σ significance and extracted cross section rest entirely on the background estimate of 0.48^{+0.16}_{-0.15} events in the narrow 10.5-13 MeV ROI. The manuscript provides no quantitative sideband measurement, Monte Carlo validation, or calibration data demonstrating that the high-energy nonlinearity correction leaves a residual background rate this low; an unmodeled component at the level of ~1 event would reduce the excess below 3σ. This assumption is load-bearing for the central claim.

Authors: The background estimate is obtained from a full Monte Carlo simulation of all known sources (radioactivity, cosmogenics, and detector effects) after applying the same nonlinearity correction and event selection as the data. This simulation has been validated against data in lower-energy sidebands (5–10 MeV) where event statistics are sufficient to test the model. The quoted background uncertainty already incorporates a dedicated component for possible residual mismodeling after the nonlinearity correction. We agree that an explicit high-energy sideband comparison would further strengthen the claim and will add a new figure and accompanying text showing data/MC agreement in the 8–10.5 MeV sideband to demonstrate the extrapolation into the ROI. revision: partial
Referee: [Cross-section extraction and comparison to theory] The reported factor 2.4^{+1.3}_{-1.0} discrepancy with the Bhattacharya et al. (2009) prediction is presented without a dedicated discussion of possible residual systematics in the energy-scale correction or event-selection efficiency at 10-13 MeV. Because the central value carries large asymmetric errors and the measurement is a single-ROI counting experiment, the discrepancy cannot yet be interpreted as a robust tension with theory.

Authors: We will insert a new paragraph in the results section that explicitly discusses the residual systematics affecting the energy scale and selection efficiency in the 10–13 MeV range. The dominant contributions (energy-scale uncertainty of ±0.3 MeV and efficiency variation of 15 %) are already folded into the reported systematic error; we will tabulate these contributions for clarity. The manuscript presents the factor 2.4 as the measured value relative to the theoretical prediction without asserting statistical tension, given the large uncertainties and single-ROI nature of the measurement. We will add explicit language stating that this is a first measurement whose central value carries substantial statistical and systematic uncertainties. revision: yes

Circularity Check

0 steps flagged

No significant circularity: direct counting measurement with independent background subtraction

full rationale

The paper reports a direct counting experiment in which the signal cross section is computed from raw observed counts in the ROI minus an independently estimated background. No derivation step reduces to a self-definition, a fitted parameter renamed as a prediction, or a load-bearing self-citation. The background rate (0.48 events) and the assignment of the six events as neutrino-like are treated as external inputs; the reported excess and cross section follow arithmetically from those inputs without circular closure. The comparison to the 2009 Bhattacharya et al. prediction is external and does not enter the measurement chain.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the background model (0.48 events) and the energy-scale calibration at high energies; no free parameters are fitted to the signal itself and no new particles or forces are introduced.

axioms (2)

domain assumption The detector response nonlinearity corrections at 10-13 MeV are accurate enough that the ROI maps correctly to 12-14.5 MeV incident neutrino energy.
Invoked to define the signal region and to compare with the 8B spectrum.
domain assumption The background estimate of 0.48 events is independent of the signal hypothesis.
Required for the 4.0 sigma significance calculation.

pith-pipeline@v0.9.0 · 6218 in / 1506 out tokens · 42072 ms · 2026-05-14T19:41:27.116845+00:00 · methodology

discussion (0)

Reference graph

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