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arxiv: 2606.25078 · v1 · pith:C5YEEFGBnew · submitted 2026-06-23 · ✦ hep-ph

Nuclear Gluon Gravitational Form Factors and Neutron Skins at the Electron-Ion Collider

Lei Wang This is my paper

Pith reviewed 2026-06-25 22:47 UTC · model grok-4.3

classification ✦ hep-ph
keywords neutron skinsgluon gravitational form factorscoherent J/psi productionelectron-ion collidernuclear structuresmall-x gluonssymmetry energy
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The pith

Coherent J/psi production at the EIC measures nuclear gluon radii to constrain neutron skins, with precision limited by gluon density calibration rather than luminosity.

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

The paper develops a radius-sum-rule framework that links the average small-x gluon radius inside nuclei, extracted from coherent quarkonium production, to neutron skin thicknesses. This offers a reaction mechanism complementary to parity-violating electron scattering for probing nuclear structure and symmetry energy. The analysis finds that J/psi production supplies enough shape information to support a competitive neutron-skin program at the Electron-Ion Collider. Precision is set by how accurately the nuclear small-x gluon density is calibrated, not by available luminosity. The cleaner Upsilon channel stays statistically limited at early EIC luminosities and requires higher data rates.

Core claim

Coherent quarkonium production at the Electron-Ion Collider can image the average small-x gluon radius of nuclei. A calibrated radius-sum-rule framework connects this gluonic radius to neutron skins while quantifying limitations from finite-dipole saturation, nuclear opacity, and instrumental resolution. The central result is that coherent J/psi production contains sufficient shape information for a competitive neutron-skin program, but its precision is controlled by the calibration of the nuclear small-x gluon density, while the cleaner Upsilon channel remains statistically limited at early EIC luminosities. The framework identifies what an EIC measurement can robustly add to symmetry-energ

What carries the argument

Calibrated radius-sum-rule framework that maps the gluonic radius imaged by coherent J/psi and Upsilon production to neutron skins after accounting for saturation, opacity, and resolution effects.

If this is right

  • Coherent J/psi production supplies enough shape information for neutron-skin measurements competitive with existing methods.
  • Measurement precision is controlled by calibration of the nuclear small-x gluon density.
  • The Upsilon channel remains statistically limited at early EIC luminosities.
  • The framework specifies the theoretical and experimental controls needed before the results can be treated as precision nuclear-structure data.
  • It identifies the concrete contribution an EIC neutron-skin measurement can make to symmetry-energy studies.

Where Pith is reading between the lines

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

  • Global fits that tighten the small-x gluon density would directly raise the precision reachable for neutron skins.
  • Cross-checks against parity-violating scattering in the same nuclei and kinematics would test the sum-rule assumptions.
  • The method could be extended to other vector mesons to verify consistency across production channels.
  • Results would feed into models of nuclear matter that link gluon distributions to neutron-proton asymmetry.

Load-bearing premise

The radius-sum-rule framework accurately maps the measured gluonic radius to neutron skins once finite-dipole saturation, nuclear opacity, and instrumental resolution are accounted for.

What would settle it

A measurement in which the neutron skin extracted from calibrated coherent J/psi data differs from the value obtained by parity-violating electron scattering by more than the combined uncertainty after gluon-density calibration would falsify the mapping.

Figures

Figures reproduced from arXiv: 2606.25078 by Lei Wang.

Figure 1
Figure 1. Figure 1: FIG. 1. Radius sum rule in position space for [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. Coherent [PITH_FULL_IMAGE:figures/full_fig_p003_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. Finite-dipole saturation produces a large but predom [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Projected constraints on the symmetry-energy slope [PITH_FULL_IMAGE:figures/full_fig_p005_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p007_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Dependence of the [PITH_FULL_IMAGE:figures/full_fig_p008_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: shows the unsmeared coherent spectra corresponding to [PITH_FULL_IMAGE:figures/full_fig_p008_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9. Stability of the coherent-radius forecast across MV-, IP-Sat-, and bCGC-like response maps for [PITH_FULL_IMAGE:figures/full_fig_p009_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10. Good–Walker decomposition for spherical [PITH_FULL_IMAGE:figures/full_fig_p010_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11. Neutron-skin correlations with the symmetry-energy slope [PITH_FULL_IMAGE:figures/full_fig_p010_11.png] view at source ↗
read the original abstract

Coherent quarkonium production at the Electron--Ion Collider can image the average small-$x$ gluon radius of nuclei, providing a reaction mechanism complementary to parity-violating electron scattering. We develop a calibrated radius-sum-rule framework that connects this gluonic radius to neutron skins and quantify the leading limitations from finite-dipole saturation, nuclear opacity, and instrumental resolution. The central result is that coherent $\Jpsi$ production contains sufficient shape information for a competitive neutron-skin program, but its precision is not limited by luminosity alone. It is instead controlled by the calibration of the nuclear small-$x$ gluon density, while the cleaner $\Ups$ channel remains statistically limited at early EIC luminosities. This framework identifies what an EIC neutron-skin measurement can robustly add to symmetry-energy studies and which theoretical and experimental controls are required before such a measurement can be interpreted as precision nuclear-structure information.

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.

Referee Report

0 major / 0 minor

Summary. The manuscript develops a calibrated radius-sum-rule framework that maps the average small-x gluon radius extracted from coherent J/psi (and Upsilon) production at the EIC to neutron skins, after corrections for finite-dipole saturation, nuclear opacity, and instrumental resolution. The central claim is that coherent J/psi production contains sufficient shape information for a competitive neutron-skin program whose precision is set by the calibration of the nuclear small-x gluon density rather than by luminosity alone, while the Upsilon channel remains statistically limited at early EIC luminosities. The framework is presented as identifying what an EIC measurement can robustly add to symmetry-energy studies.

Significance. If the result holds, the work supplies a gluon-based complement to parity-violating electron scattering for neutron-skin extraction, directly relevant to symmetry-energy constraints. A clear strength is the explicit identification of gluon-density calibration as the dominant uncertainty, with the sum-rule mapping treated as the quantity to be calibrated rather than asserted to be independent of input data.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive review and recommendation to accept the manuscript.

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained

full rationale

The paper develops a calibrated radius-sum-rule framework mapping gluonic radius from coherent quarkonium production to neutron skins, but explicitly flags the gluon-density calibration step as the dominant uncertainty rather than deriving the sum-rule output from itself. No load-bearing step reduces by construction to fitted inputs or self-citations; the central claim treats the sum-rule as an independent mapping whose precision is limited by external calibration. The provided abstract and description contain no self-definitional equations, fitted predictions, or uniqueness theorems imported from prior author work. This is the normal case of an honest non-finding.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the validity of the radius-sum-rule and the ability to quantify the listed limitations; without the full text these remain domain assumptions whose independent support is not visible.

axioms (2)
  • domain assumption A radius-sum-rule exists that maps the average small-x gluon radius extracted from coherent quarkonium production to neutron skin thickness.
    This is the load-bearing relation introduced in the framework.
  • domain assumption Finite-dipole saturation, nuclear opacity, and instrumental resolution can be quantified and do not invalidate the shape information in J/psi data.
    The abstract states these are the leading limitations that must be controlled.

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Sub-eikonal stress and model dependence of the small-$x$ gluon D-term

    hep-ph 2026-07 unverdicted novelty 7.0

    The gluon D-term at small x is a next-to-eikonal stress observable whose sign is not determined by the dipole or saturation profile.

Reference graph

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