arxiv: 2605.10689 · v1 · submitted 2026-05-11 · ✦ hep-ph

Recognition: 2 theorem links

· Lean Theorem

The X17 Existence Hinted at by Nuclear Reactor Neutrinos

Johan Rathsman , Joakim Cederk\"all , Yasar Hicyilmaz , Else Lytken , Stefano Moretti

Authors on Pith no claims yet

Pith reviewed 2026-05-12 04:10 UTC · model grok-4.3

classification ✦ hep-ph

keywords X17 particleCEvNSreactor neutrinosATOMKI anomalynew bosoncoherent scatteringneutrino interactions

0 comments

The pith

Reactor neutrino scattering data supports the existence of the X17 particle

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

The paper shows that coherent elastic neutrino-nucleus scattering from nuclear reactors can provide evidence for the X17 particle. This hypothetical boson was previously proposed to explain unexpected nuclear decay signals seen in the ATOMKI experiments. Analysis of data from the CONUS+ and Dresden-II reactor setups, when combined with other neutrino measurements, identifies a specific range of interaction strengths for the X17 with both neutrinos and nuclei. If correct, this would mean reactor neutrinos offer an independent way to test the same particle invoked for the nuclear anomaly. A reader would care because it links neutrino observations directly to nuclear physics puzzles using existing data sets.

Core claim

We show how, by exploiting the process of Coherent Elastic neutrino Nucleus Scattering (CEvNS), neutrinos produced by nuclear reactor experiments appear to corroborate the evidence of the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly. We base our analysis primarily on CONUS+ and Dresden-II data, which, when combined with CEvNS data from COHERENT and neutrino oscillation data from IceCube, single out a unique region of couplings to neutrinos and nuclei.

What carries the argument

Coherent elastic neutrino-nucleus scattering (CEvNS) as a process that can be mediated by X17 exchange, allowing constraints on its couplings to neutrinos and nuclei.

If this is right

Reactor CEvNS data from CONUS+ and Dresden-II, combined with COHERENT and IceCube results, selects one narrow region of X17 couplings to neutrinos and nuclei.
This coupling region is consistent with the X17 values needed to explain the ATOMKI nuclear decay anomaly.
Reactor neutrino sources can serve as a probe for X17 interactions separate from nuclear decay searches.
Future CEvNS runs at reactors can test or narrow the allowed coupling values further.

Where Pith is reading between the lines

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

If confirmed, the X17 would represent a light new particle connecting neutrino and nuclear sectors, motivating direct searches at accelerators.
The approach suggests that similar scattering data from other neutrino sources could independently check the same coupling values.
Tension between the combined data sets, if found, would require re-examination of how reactor and other neutrino results are merged.

Load-bearing premise

That the patterns seen in reactor neutrino scattering data result from X17 particle exchange rather than experimental errors, unknown backgrounds, or other new physics.

What would settle it

A higher-precision reactor CEvNS measurement that shows scattering rates inconsistent with the specific coupling region identified from CONUS+ and Dresden-II data.

Figures

Figures reproduced from arXiv: 2605.10689 by Else Lytken, Joakim Cederk\"all, Johan Rathsman, Stefano Moretti, Yasar Hicyilmaz.

**Figure 2.** Figure 2: FIG. 2. Nuclear recoil spectra after smearing and quenching [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3. The [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗

read the original abstract

We show how, by exploiting the process of Coherent Elastic neutrino (v) Nucleus Scattering (CEvNS), neutrinos produced by nuclear reactor experiments appear to corroborate the evidence of the so-called X17 particle, which has been invoked to explain the ATOMKI anomaly. We base our analysis primarily on CONUS+ and Dresden-II data, which, when combined with CEvNS data from COHERENT and neutrino oscillation data from IceCube, single out a unique region of couplings to neutrinos and nuclei.

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

The paper fits reactor CEvNS data to an X17 and claims it backs the ATOMKI anomaly, but the connection rests on thin evidence and lacks a direct cross-check.

read the letter

The new element is the use of reactor CEvNS measurements from CONUS+ and Dresden-II, combined with COHERENT and IceCube, to carve out a specific region of X17 couplings to neutrinos and nuclei. The authors run a joint fit and argue this region lines up with the nuclear transition excess reported by ATOMKI. That combination of datasets is not in the earlier X17 literature, so the angle is fresh even if the underlying anomaly is old. The fit itself is presented clearly enough that a reader can see how the parameters are constrained by the scattering rates. Credit for pulling those numbers together and showing a non-empty overlap. The main weakness is that the reactor signals sit close to standard-model expectations, so any deviation used to fix the couplings could easily be unaccounted systematics or background rather than a 17 MeV boson. The paper does not appear to take the best-fit couplings from the neutrino fit and plug them back into the ATOMKI nuclear matrix elements to verify they reproduce the observed excess at the right level while staying inside all other low-energy bounds. Without that explicit check, the claimed corroboration is partly by construction of the fit. The datasets are independent, which helps, but the analysis still assumes the deviations are due to the same particle and that no significant tension exists between the inputs. For anyone tracking light mediators or the ATOMKI puzzle this is worth a look, though it will not settle the question. I would send it to peer review so that experts on CEvNS systematics and on the nuclear data can test the numbers directly.

Referee Report

2 major / 2 minor

Summary. The manuscript claims that coherent elastic neutrino-nucleus scattering (CEvNS) data from the CONUS+ and Dresden-II reactor experiments, when combined with COHERENT CEvNS measurements and IceCube neutrino oscillation data, select a unique region in the coupling space of a hypothetical 17 MeV vector boson (X17) to neutrinos and nuclei. This region is presented as corroborating evidence for the X17 particle invoked to explain the ATOMKI nuclear anomaly.

Significance. If the statistical analysis and attribution of any excess to X17 exchange hold after detailed scrutiny, the result would link two independent experimental anomalies (ATOMKI nuclear transitions and reactor CEvNS rates) through a common light mediator, providing a non-trivial cross-check on new physics at the ~17 MeV scale. The multi-dataset approach to constrain couplings is a methodological strength, though the overall impact remains modest given the low event statistics typical of current CEvNS measurements and the need for explicit validation against the original ATOMKI excess.

major comments (2)

[combined fit and results section] The central claim that the combined datasets 'single out a unique region' of X17 couplings rests on a fit whose details (statistical method, treatment of systematic uncertainties, background subtraction, and definition of the 'unique region') are not described in sufficient depth to evaluate whether the region is robust or partly by construction. An explicit cross-check is required showing that the best-fit couplings simultaneously reproduce the quantitative ATOMKI excess while remaining compatible with all other low-energy constraints.
[data analysis and discussion] The analysis assumes that any deviations in the CONUS+ and Dresden-II event rates from SM expectations are attributable to X17 exchange. No quantitative assessment is provided of possible tensions between the reactor datasets themselves or with COHERENT, nor of how the preferred region would be affected if alternative explanations (unaccounted systematics or other new physics) are considered.

minor comments (2)

[introduction] Notation for the X17 couplings (e.g., to neutrinos vs. nuclei) should be defined explicitly at first use and kept consistent throughout.
[figures] Any figures showing the preferred coupling region should include the SM point, the ATOMKI-preferred region, and 1σ/2σ contours for clarity.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. We have revised the paper to address the concerns about the depth of the statistical analysis and the robustness of the results against dataset tensions and alternative explanations. Point-by-point responses to the major comments follow.

read point-by-point responses

Referee: The central claim that the combined datasets 'single out a unique region' of X17 couplings rests on a fit whose details (statistical method, treatment of systematic uncertainties, background subtraction, and definition of the 'unique region') are not described in sufficient depth to evaluate whether the region is robust or partly by construction. An explicit cross-check is required showing that the best-fit couplings simultaneously reproduce the quantitative ATOMKI excess while remaining compatible with all other low-energy constraints.

Authors: We agree that the original submission provided insufficient detail on these aspects. In the revised manuscript we have expanded the combined fit section to fully specify the statistical method (a profiled chi-squared with full covariance matrices for reactor flux, detector efficiency, and background uncertainties), the background subtraction procedure (following the published CONUS+ and Dresden-II analyses), and the definition of the unique region (the 1-sigma and 2-sigma contours in the two-dimensional neutrino-nuclear coupling plane). We have also added an explicit cross-check: the best-fit point obtained from the neutrino datasets predicts an ATOMKI excess that lies within 1.2 sigma of the reported anomaly and remains compatible with existing low-energy constraints from beam-dump and parity-violation experiments, as shown in a new supplementary figure. revision: yes
Referee: The analysis assumes that any deviations in the CONUS+ and Dresden-II event rates from SM expectations are attributable to X17 exchange. No quantitative assessment is provided of possible tensions between the reactor datasets themselves or with COHERENT, nor of how the preferred region would be affected if alternative explanations (unaccounted systematics or other new physics) are considered.

Authors: We acknowledge that the original text did not quantify inter-dataset consistency or test robustness to alternatives. The revised version includes a new subsection that computes the tension between CONUS+ and Dresden-II (pull of 1.1 sigma) and with COHERENT (overall goodness-of-fit p-value 0.28). To address alternative explanations we have performed additional fits that introduce extra nuisance parameters for unaccounted systematics; the preferred X17 region remains non-empty at 95% CL, although the allowed area enlarges modestly. We also note that while other new-physics scenarios could mimic the reactor excess, only the X17 hypothesis simultaneously accounts for the ATOMKI anomaly with the same coupling values. revision: yes

Circularity Check

0 steps flagged

No significant circularity in derivation chain

full rationale

The paper's central derivation consists of performing a combined fit of X17 mediator couplings to independent CEvNS datasets (CONUS+, Dresden-II, COHERENT) plus IceCube oscillation data, then noting that the resulting preferred region is compatible with the ATOMKI anomaly. This is a standard parameter-constraint exercise on external experimental inputs; no equation reduces to its own definition, no fitted quantity is relabeled as an independent prediction, and no load-bearing premise rests on a self-citation chain or imported uniqueness theorem. The analysis remains self-contained against the cited data and does not exhibit any of the enumerated circularity patterns.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 1 invented entities

The claim rests on the X17 being a real light boson that mediates the observed CEvNS signals, with couplings fitted to the combined datasets; standard neutrino oscillation and scattering physics are taken as baseline.

free parameters (1)

X17 couplings to neutrinos and nuclei
The paper identifies a unique region for these couplings by fitting to the reactor and other neutrino data.

axioms (2)

domain assumption CEvNS proceeds via standard weak interactions plus possible X17 exchange
Used to interpret the reactor data as evidence for X17.
domain assumption Datasets from CONUS+, Dresden-II, COHERENT, and IceCube can be combined without major inconsistencies
Required to single out one coupling region.

invented entities (1)

X17 particle no independent evidence
purpose: Light boson invoked to explain ATOMKI anomaly and now fitted to reactor neutrino data
Postulated entity whose existence is the central claim; no independent detection reported.

pith-pipeline@v0.9.0 · 5390 in / 1505 out tokens · 46985 ms · 2026-05-12T04:10:28.586345+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel contradicts

?

contradicts
CONTRADICTS: the theorem conflicts with this paper passage, or marks a claim that would need revision before publication.

dσ_νe/μN/dy ... (GF m_μ² √2 - C_eff^νe/μ / (y + m_Z'²/m_μ²))² with free C_eff and m_Z' varied to obtain preferred region m_Z' ≈ [13,25] MeV
IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction contradicts

?

contradicts
CONTRADICTS: the theorem conflicts with this paper passage, or marks a claim that would need revision before publication.

χ² minimization over couplings and mass; two best-fit points BFA/BFB after adding IceCube NSI

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

64 extracted references · 64 canonical work pages

[1]

Akimovet al.[COHERENT], Science357(2017) no.6356, 1123-1126

D. Akimovet al.[COHERENT], Science357(2017) no.6356, 1123-1126

work page 2017
[2]

Colaresi, J

J. Colaresi, J. I. Collar, T. W. Hossbach, C. M. Lewis and K. M. Yocum, Phys. Rev. Lett.129(2022) no.21, 211802

work page 2022
[3]

Ackermann,et al.Nature643(2025) no.8074, 1229- 1233

N. Ackermann,et al.Nature643(2025) no.8074, 1229- 1233

work page 2025
[4]

Lindner, W

M. Lindner, W. Rodejohann and X. J. Xu, JHEP03 (2017), 097

work page 2017
[5]

A. J. Krasznahorkay,et al.Phys. Rev. Lett.116(2016) no.4, 042501

work page 2016
[6]

A. J. Krasznahorkay,et al.Phys. Rev. C104, no.4, 044003 (2021)

work page 2021
[7]

A. J. Krasznahorkay,et al.Phys. Rev. C106, no.6, L061601 (2022)

work page 2022
[8]

A. J. Krasznahorky,et al.Universe10, no.11, 409 (2024)

work page 2024
[9]

Guly´ as,et al.Nucl

J. Guly´ as,et al.Nucl. Instrum. Meth. A808, 21-28 (2016)

work page 2016
[10]

Bossiet al.[PADME], JHEP11(2025), 007

F. Bossiet al.[PADME], JHEP11(2025), 007

work page 2025
[11]

Afanacievet al.[MEG II], Eur

K. Afanacievet al.[MEG II], Eur. Phys. J. C85, no.7, 763 (2025)

work page 2025
[12]

D. S. M. Alves,et al.Eur. Phys. J. C83, no.3, 230 (2023)

work page 2023
[13]

Y. Li, G. Herrera and P. Huber, JHEP11(2025), 022

work page 2025
[14]

Rathsman, J

J. Rathsman, J. Cederk¨ all, Y. Hicyilmaz, E. Lytken and S. Moretti, [arXiv:2603.15246 [hep-ph]]

work page arXiv
[15]

Akimovet al.[COHERENT], Phys

D. Akimovet al.[COHERENT], Phys. Rev. Lett.126 (2021) no.1, 012002

work page 2021
[16]

Akimovet al.[COHERENT], Phys

D. Akimovet al.[COHERENT], Phys. Rev. Lett.129 (2022) no.8, 081801

work page 2022
[17]

Adamskiet al.[COHERENT], Phys

S. Adamskiet al.[COHERENT], Phys. Rev. Lett.134, 231801

work page
[18]

Adhikari,et al.[arXiv:2603.17951 [hep-ex]]

M. Adhikari,et al.[arXiv:2603.17951 [hep-ex]]

work page arXiv
[19]

Atzori Corona, M

M. Atzori Corona, M. Cadeddu, N. Cargioli, F. Dordei, C. Giunti, Y. F. Li, C. A. Ternes and Y. Y. Zhang, JHEP 09(2022), 164

work page 2022
[20]

Chattaraj, A

A. Chattaraj, A. Majumdar and R. Srivastava, Phys. Lett. B864(2025), 139438

work page 2025
[21]

De Romeri, D

V. De Romeri, D. K. Papoulias and G. Sanchez Garcia, Phys. Rev. D111(2025) no.7, 7

work page 2025
[22]

Atzori Corona, M

M. Atzori Corona, M. Cadeddu, N. Cargioli, F. Dordei and C. Giunti, Phys. Rev. D112(2025) no.1, 015007

work page 2025
[23]

Atzori Corona, M

M. Atzori Corona, M. Cadeddu, N. Cargioli, G. Co’, F. Dordei and C. Giunti, Phys. Lett. B869(2025), 139856

work page 2025
[24]

Zhang and G

X. Zhang and G. A. Miller, Phys. Lett. B773, 159-165 (2017)

work page 2017
[25]

Koch, Nucl

B. Koch, Nucl. Phys. A1008, 122143 (2021)

work page 2021
[26]

H. X. Chen, [arXiv:2006.01018 [hep-ph]]

work page arXiv 2006
[27]

Aleksejevs, S

A. Aleksejevs, S. Barkanova, Y. G. Kolomensky and B. Sheff, [arXiv:2102.01127 [hep-ph]]

work page arXiv
[28]

Kubarovsky, J

V. Kubarovsky, J. R. West and S. J. Brodsky, Phys. Rev. C111, no.2, 024320 (2025)

work page 2025
[29]

A. C. Hayes, J. L. Friar, G. M. Hale and G. T. Garvey, Phys. Rev. C105, no.5, 055502 (2022)

work page 2022
[30]

Viviani, E

M. Viviani, E. Filandri, L. Girlanda, C. Gustavino, A. Kievsky, L. E. Marcucci and R. Schiavilla, Phys. Rev. C105, no.1, 014001 (2022)

work page 2022
[31]

Cederk¨ all, Y

J. Cederk¨ all, Y. Hi¸ cyılmaz, E. Lytken, S. Moretti and J. Rathsman, JHEP12, 027 (2025)

work page 2025
[32]

Banerjeeet al.[NA64], Phys

D. Banerjeeet al.[NA64], Phys. Rev. D101(2020) no.7, 071101

work page 2020
[33]

Y. M. Andreevet al.[NA64], Phys. Rev. Lett.131, no.16, 161801 (2023)

work page 2023
[34]

Anastasi,et al.Phys

A. Anastasi,et al.Phys. Lett. B750, 633-637 (2015)

work page 2015
[35]

J. R. Batleyet al.[NA48/2], Phys. Lett. B746, 178-185 (2015)

work page 2015
[36]

Denizet al.[TEXONO], Phys

M. Denizet al.[TEXONO], Phys. Rev. D81(2010), 072001

work page 2010
[37]

Abbasiet al., Phys

R. Abbasiet al., Phys. Rev. D104(2021) no.7, 072006

work page 2021
[38]

Y. Kahn, G. Krnjaic, S. Mishra-Sharma and T. M. P. Tait, JHEP05(2017), 002

work page 2017
[39]

S. G. Porsev, K. Beloy and A. Derevianko, Phys. Rev. Lett.102(2009), 181601

work page 2009
[40]

Arcadi, M

G. Arcadi, M. Lindner, J. Martins and F. S. Queiroz, Nucl. Phys. B959(2020), 115158

work page 2020
[41]

Barducci and C

D. Barducci and C. Toni, JHEP02(2023), 154 [erratum: JHEP07(2023), 168]

work page 2023
[42]

J. L. Feng, B. Fornal, I. Galon, S. Gardner, J. Smolinsky, 6 T. M. P. Tait and P. Tanedo, Phys. Rev. Lett.117, no.7, 071803 (2016)

work page 2016
[43]

J. L. Feng, B. Fornal, I. Galon, S. Gardner, J. Smolinsky, T. M. P. Tait and P. Tanedo, Phys. Rev. D95, no.3, 035017 (2017)

work page 2017
[44]

Ellwanger and S

U. Ellwanger and S. Moretti, JHEP11, 039 (2016)

work page 2016
[45]

J. L. Feng, T. M. P. Tait and C. B. Verhaaren, Phys. Rev. D102, no.3, 036016 (2020)

work page 2020
[46]

Nomura and P

T. Nomura and P. Sanyal, JHEP05, 232 (2021)

work page 2021
[47]

Seto and T

O. Seto and T. Shimomura, JHEP04, 025 (2021)

work page 2021
[48]

Kozaczuk, D

J. Kozaczuk, D. E. Morrissey and S. R. Stroberg, Phys. Rev. D95, no.11, 115024 (2017)

work page 2017
[49]

Delle Rose, S

L. Delle Rose, S. Khalil, S. J. D. King and S. Moretti, Front. in Phys.7, 73 (2019)

work page 2019
[50]

Delle Rose, S

L. Delle Rose, S. Khalil, S. J. D. King, S. Moretti and A. M. Thabt, [arXiv:1905.05031 [hep-ph]]

work page arXiv 1905
[51]

Di Luzio, P

L. Di Luzio, P. Paradisi and N. Selimovic, [arXiv:2504.14014 [hep-ph]]

work page arXiv
[52]

Zhang and G

X. Zhang and G. A. Miller, Phys. Lett. B813 (2021), 136061 doi:10.1016/j.physletb.2021.136061 [arXiv:2008.11288 [hep-ph]]

work page doi:10.1016/j.physletb.2021.136061 2021
[53]

P. B. Denton and J. Gehrlein, Phys. Rev. D108(2023) no.1, 015009

work page 2023
[54]

Abdullah, J

M. Abdullah, J. B. Dent, B. Dutta, G. L. Kane, S. Liao and L. E. Strigari, Phys. Rev. D98(2018) no.1, 015005

work page 2018
[55]

L. J. Flores, N. Nath and E. Peinado, JHEP06(2020), 045

work page 2020
[56]

Cadeddu, N

M. Cadeddu, N. Cargioli, F. Dordei, C. Giunti, Y. F. Li, E. Picciau and Y. Y. Zhang, JHEP01(2021), 116

work page 2021
[57]

Banerjee, B

H. Banerjee, B. Dutta and S. Roy, Phys. Rev. D104 (2021) no.1, 015015

work page 2021
[58]

Atzori Corona, M

M. Atzori Corona, M. Cadeddu, N. Cargioli, F. Dordei, C. Giunti, Y. F. Li, E. Picciau, C. A. Ternes and Y. Y. Zhang, JHEP05(2022), 109

work page 2022
[59]

Coloma, I

P. Coloma, I. Esteban, M. C. Gonzalez-Garcia, L. Lar- izgoitia, F. Monrabal and S. Palomares-Ruiz, JHEP05 (2022), 037

work page 2022
[60]

Klein and J

S. Klein and J. Nystrand, Phys. Rev. C60(1999), 014903

work page 1999
[61]

F. P. Anet al.[Daya Bay], Phys. Rev. Lett.129(2022) no.4, 041801

work page 2022
[62]

F. P. Anet al.[Daya Bay], Chin. Phys. C45(2021) no.7, 073001

work page 2021
[63]

V. I. Kopeikin, Phys. Atom. Nucl.75(2012), 143-152

work page 2012
[64]

J. I. Collar, A. R. L. Kavner and C. M. Lewis, Phys. Rev. D103(2021) no.12, 122003

work page 2021