arxiv: 2605.00866 · v1 · submitted 2026-04-22 · ✦ hep-ph · hep-ex· hep-th· nucl-ex· nucl-th

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Nuclear geometry driven symmetry plane correlations in OO and Ne--Ne collisions at the Large Hadron Collider

Suraj Prasad , Raghunath Sahoo

Authors on Pith no claims yet

Pith reviewed 2026-05-10 00:14 UTC · model grok-4.3

classification ✦ hep-ph hep-exhep-thnucl-exnucl-th

keywords symmetry plane correlationsnuclear geometryoxygen-oxygen collisionsneon-neon collisionsnuclear deformationtetrahedral structureheavy-ion collisionsAMPT model

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The pith

Symmetry plane correlations in OO and Ne-Ne collisions at the LHC are driven by the distinct nuclear shapes of oxygen and neon.

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

The paper examines whether symmetry plane correlations measured in high-energy light-ion collisions can be traced directly to the geometries of the colliding nuclei. It simulates oxygen-oxygen and neon-neon collisions at 5.36 TeV with nuclear configurations taken from NLEFT and PGCM calculations, then extracts two specific correlators using the AMPT transport model. The calculations yield a clear pattern: neon-neon events produce larger values of the four-plane correlator while oxygen-oxygen events produce larger values of the six-plane correlator. These opposing trends are interpreted as signatures of a strongly deformed neon-20 nucleus and a tetrahedral oxygen-16 nucleus. The work therefore proposes that certain symmetry-plane observables can serve as direct probes of nuclear structure in collider data.

Core claim

Ne-Ne collisions exhibit larger ⟨cos[4(ψ₂ - ψ₄)]⟩_GE values than OO collisions, whereas ⟨cos[6(ψ₃ - ψ₆)]⟩_GE is larger in OO than in Ne-Ne collisions. This behavior is obtained when nuclear geometries from Nuclear Lattice Effective Field Theory and Projected Generator Coordinate Method are used as input to the AMPT model. Events selected in tip-tip and body-body configurations further support the same ordering. The pattern is taken to indicate a strongly deformed shape of the ²⁰Ne nucleus and a tetrahedral structure of the ¹⁶O nucleus.

What carries the argument

Participant-plane correlations generated by the nuclear overlap geometries of ¹⁶O and ²⁰Ne, read out through the generalized-event symmetry-plane correlators ⟨cos[4(ψ₂ - ψ₄)]⟩_GE and ⟨cos[6(ψ₃ - ψ₆)]⟩_GE.

Load-bearing premise

The measured differences in the two symmetry-plane correlators are driven primarily by the input nuclear geometries rather than by model-specific dynamics or medium response in AMPT.

What would settle it

Experimental measurements of the two SPC observables in real OO and Ne-Ne collisions at the LHC that show the opposite ordering or no significant difference between the two systems would falsify the geometry-driven interpretation.

Figures

Figures reproduced from arXiv: 2605.00866 by Raghunath Sahoo, Suraj Prasad.

**Figure 2.** Figure 2: FIG. 2. The ratio of SPCs in Ne–Ne to OO collisions for [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗

**Figure 3.** Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4. The ratio of SPCs in Ne–Ne to OO collisions for [PITH_FULL_IMAGE:figures/full_fig_p005_4.png] view at source ↗

read the original abstract

Symmetry-plane correlations (SPCs) are key observables sensitive to the medium's transport properties and are driven by participant-plane correlations (PPCs) in the nuclear overlap region. This study explores the possibility of nuclear-geometry-driven SPCs in Oxygen--Oxygen (OO) and Neon--Neon (Ne--Ne) collisions at $\sqrt{s_{\rm NN}}=5.36$ TeV using nuclear geometry simulations based on Nuclear Lattice Effective Field Theory (NLEFT) and Projected Generator Coordinate Method (PGCM) configurations. We investigate $\langle \cos[4(\psi_2 - \psi_4)]\rangle_{\rm GE}$ and $\langle \cos[6(\psi_3 - \psi_6)]\rangle_{\rm GE}$ in OO and Ne--Ne collisions at $\sqrt{s_{\rm NN}}=5.36$ TeV using the A Multi-Phase Transport (AMPT) model. We find that Ne--Ne collisions exhibit larger $\langle \cos[4(\psi_2 - \psi_4)]\rangle_{\rm GE}$ values than OO collisions, whereas $\langle \cos[6(\psi_3 - \psi_6)]\rangle_{\rm GE}$ is larger in OO than in Ne--Ne collisions. This behavior indicates a strongly deformed shape of the $^{20}$Ne nucleus and a tetrahedral structure of the $^{16}$O nucleus. We also explore SPCs for events with tip-tip and body-body collision configurations, which further support these findings.

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 reports an inversion in two symmetry-plane correlations between OO and Ne-Ne in AMPT runs with NLEFT/PGCM inputs and ties it to tetrahedral oxygen versus deformed neon, but the link rests on a single transport model without cross-checks.

read the letter

The new piece here is the concrete mapping of established SPC observables onto NLEFT/PGCM geometries for these two light systems at LHC energy. They run AMPT, select tip-tip and body-body orientations, and show that ⟨cos[4(ψ₂-ψ₄)]⟩_GE is larger in Ne-Ne while ⟨cos[6(ψ₃-ψ₆)]⟩_GE is larger in OO. That pattern is not in the earlier literature they cite, so the application itself is fresh. The orientation cuts give some internal consistency check that the signal tracks the input shape rather than just overall multiplicity. That part is useful for people thinking about initial-state modeling in small systems. The soft spot is exactly the one the stress-test flags: the ordering is attributed to nuclear geometry, yet everything runs through AMPT only. No hydrodynamic comparison, no variation of parton scattering or coalescence parameters, and no baseline with spherical inputs appear in the abstract or the described results. Without those, it is hard to know whether the inversion survives changes in medium response or is partly an artifact of how AMPT handles the different participant geometries and system sizes. The abstract also gives no error bars or quantitative washout estimates, so the size of the geometry-driven effect stays unclear. This work is aimed at heavy-ion physicists who already use symmetry-plane correlations to constrain initial conditions. A reader in that group can pull the idea and test it with their own code, but the current evidence is not yet strong enough to treat the shape assignment as settled. I would send it to peer review so the model-dependence question gets proper scrutiny; the core idea is worth exploring even if the present version needs more validation.

Referee Report

2 major / 2 minor

Summary. The manuscript investigates symmetry plane correlations (SPCs) in OO and Ne-Ne collisions at √s_NN=5.36 TeV by combining nuclear geometries from Nuclear Lattice Effective Field Theory (NLEFT) and Projected Generator Coordinate Method (PGCM) with the AMPT transport model. It reports larger ⟨cos[4(ψ₂ - ψ₄)]⟩_GE in Ne-Ne than OO collisions and the reverse ordering for ⟨cos[6(ψ₃ - ψ₆)]⟩_GE, interpreting these differences as direct signatures of strong deformation in ²⁰Ne and tetrahedral structure in ¹⁶O. Tip-tip and body-body orientation selections are used to further support the geometry-driven interpretation.

Significance. If the central claim is robust, the work would establish SPCs as a practical probe of nuclear shapes in small systems at the LHC, linking ab initio nuclear structure inputs to final-state observables. The adoption of NLEFT/PGCM configurations is a clear strength, providing a more microscopic foundation than simpler models. This could open avenues for collider-based nuclear structure studies, though the significance hinges on demonstrating that the reported orderings are not artifacts of the chosen transport dynamics.

major comments (2)

[Abstract] Abstract: The claim that the SPC orderings 'indicate a strongly deformed shape of the ²⁰Ne nucleus and a tetrahedral structure of the ¹⁶O nucleus' is load-bearing for the paper's conclusion. This attribution assumes the differences arise primarily from the input geometries rather than AMPT-specific features (parton scattering, coalescence, resonance decays, or final-state rescattering). No parameter variations in AMPT, no comparisons to hydrodynamic evolution, and no quantitative assessment of signal preservation are described, leaving the model fidelity unverified.
[Tip-tip and body-body analysis] Tip-tip and body-body analysis: The orientation-selected results test intra-system effects but remain entirely within the AMPT framework. They therefore do not isolate nuclear geometry from transport-model response and cannot rule out the possibility that the inter-system ordering (Ne-Ne vs. OO) could be generated by AMPT dynamics even for identical initial geometries.

minor comments (2)

[Abstract] Abstract: Simulation outputs are presented without error bars, statistical uncertainties, or baseline comparisons, which prevents quantitative evaluation of the reported differences.
[Notation] Notation: The subscript GE on the averaged SPCs is used without an explicit definition in the provided summary; clarifying whether it denotes a specific event class or averaging procedure would improve readability.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful review and constructive feedback on our manuscript. We address the major comments point by point below, acknowledging the model-dependence concerns while defending the geometric interpretation based on the distinct patterns and ab initio inputs. We propose targeted revisions to temper claims and add caveats.

read point-by-point responses

Referee: [Abstract] Abstract: The claim that the SPC orderings 'indicate a strongly deformed shape of the ²⁰Ne nucleus and a tetrahedral structure of the ¹⁶O nucleus' is load-bearing for the paper's conclusion. This attribution assumes the differences arise primarily from the input geometries rather than AMPT-specific features (parton scattering, coalescence, resonance decays, or final-state rescattering). No parameter variations in AMPT, no comparisons to hydrodynamic evolution, and no quantitative assessment of signal preservation are described, leaving the model fidelity unverified.

Authors: We acknowledge that the manuscript relies on a single transport model (AMPT) without parameter scans or hydrodynamic comparisons, so the attribution to nuclear geometry is not fully model-independent. However, the observed reversal in SPC ordering between the two systems—larger ⟨cos[4(ψ₂ - ψ₄)]⟩_GE in Ne-Ne and larger ⟨cos[6(ψ₃ - ψ₆)]⟩_GE in OO—matches the qualitative expectations from the distinct ab initio geometries (deformed ²⁰Ne vs. tetrahedral ¹⁶O) provided by NLEFT/PGCM. The same AMPT settings are applied to both collision systems, isolating the effect to the initial nuclear configurations. We will revise the abstract to replace 'indicate' with 'suggest' and add a dedicated paragraph in the discussion section on model assumptions, the lack of parameter variations, and the value of future cross-checks with hydrodynamics. This makes the claims appropriately cautious without altering the core results. revision: partial
Referee: [Tip-tip and body-body analysis] Tip-tip and body-body analysis: The orientation-selected results test intra-system effects but remain entirely within the AMPT framework. They therefore do not isolate nuclear geometry from transport-model response and cannot rule out the possibility that the inter-system ordering (Ne-Ne vs. OO) could be generated by AMPT dynamics even for identical initial geometries.

Authors: We agree that the tip-tip and body-body selections are performed within AMPT and do not provide a complete decoupling of geometry from transport dynamics. Nevertheless, because identical AMPT parameters are used for both OO and Ne-Ne, any inter-system difference in SPC ordering must originate from the differing input nuclear geometries. The orientation-dependent variations within each system further demonstrate that the SPCs respond to the collision geometry in a manner consistent with the nuclear shapes. We will add a clarifying sentence in the conclusions noting the framework dependence and recommending future studies with alternative models or identical-geometry tests. We do not intend to generate artificial identical geometries for cross-system comparison, as this would deviate from the ab initio approach central to the work. revision: partial

Circularity Check

0 steps flagged

No significant circularity; derivation uses external nuclear geometries and transport model without reduction to inputs

full rationale

The paper inputs nuclear configurations from NLEFT and PGCM into the AMPT model, computes SPC observables, and reports differences between OO and Ne-Ne systems. These differences are interpreted as supporting the input geometries (deformed 20Ne, tetrahedral 16O), but the chain is a forward simulation rather than a fit or self-definition. No parameters are tuned to the target SPC values, no equations reduce by construction to the inputs, and no self-citation chain carries the central claim. The analysis remains self-contained against the external benchmarks of the nuclear-structure models and AMPT; any concern about geometry vs. medium-response dominance is a question of model validation, not circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the fidelity of two nuclear-structure frameworks and one transport model whose internal assumptions are not independently validated within the paper.

axioms (2)

domain assumption NLEFT and PGCM nuclear configurations accurately represent the ground-state geometries of 16O and 20Ne.
These configurations are taken as input for the collision simulations.
domain assumption AMPT evolution preserves the participant-plane correlations sufficiently to allow geometry-driven SPCs to be observed.
The transport step is required to translate geometry into final-state observables.

pith-pipeline@v0.9.0 · 5588 in / 1320 out tokens · 49986 ms · 2026-05-10T00:14:01.869702+00:00 · methodology

discussion (0)

Reference graph

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