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arxiv: 2605.13356 · v1 · pith:AXFKS553new · submitted 2026-05-13 · ⚛️ nucl-th

Anomalous large-angle α-scattering in a single-folding model with microscopic densities

A. -G. Serban , F. Salvat-Pujol , N. Sandulescu , P. Marevi\'c This is my paper

Pith reviewed 2026-05-14 18:29 UTC · model grok-4.3

classification ⚛️ nucl-th
keywords alpha scatteringanomalous large-angle scatteringsingle-folding modelmicroscopic densitiesmean-field modelssd-shell nucleiN=Z nucleialpha-nucleon interaction
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The pith

A single-folding model with microscopic mean-field densities reproduces anomalous large-angle alpha scattering in sd-shell N=Z nuclei using a unified parameter set where only two terms vary with mass number.

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

The paper tests whether the single-folding model can explain the anomalous enhancement of alpha-particle scattering cross sections at large angles for N=Z nuclei in the sd shell. It folds a Gaussian alpha-nucleon interaction, with energy dependence and range fixed from earlier work, with nuclear densities from both relativistic and non-relativistic mean-field calculations. The calculations match experimental data reasonably well when only two parameters in the interaction are allowed to change with the mass of the target nucleus. A sympathetic reader would care because this indicates that the density profiles already generated by mean-field theories contain the structural features needed to produce the backward-angle anomaly, providing a more microscopic description of alpha reactions without heavy phenomenological tuning.

Core claim

We investigate anomalous large-angle scattering of alpha particles from N=Z nuclei within the single-folding model. Differential cross sections are calculated by folding a Gaussian alpha-nucleon interaction with nuclear density distributions obtained from both relativistic and non-relativistic mean-field models. The folding employs a Gaussian-form alpha-nucleon interaction whose energy dependence and range are constrained by previous theoretical studies. The results show that ALAS in sd-shell nuclei is reasonably well reproduced using the microscopic densities together with an alpha-nucleon interaction characterized by a unified parameter set in which only two parameters vary with the mass.

What carries the argument

The single-folding procedure that convolves the Gaussian alpha-nucleon interaction with microscopic nuclear density distributions from mean-field models.

Load-bearing premise

The Gaussian alpha-nucleon interaction with its constrained energy dependence and range, when folded with mean-field densities, captures the essential physics of ALAS without needing further adjustments beyond the two mass-dependent parameters.

What would settle it

Measured differential cross sections at large scattering angles for an additional sd-shell N=Z nucleus that lie well outside the range produced by the model after the two mass-dependent parameters are fixed would falsify the reproduction claim.

Figures

Figures reproduced from arXiv: 2605.13356 by A. -G. Serban, F. Salvat-Pujol, N. Sandulescu, P. Marevi\'c.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p007_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: shows the densities obtained from the QMC+QCM calculations for 20Ne, 24Mg, and 28Si, whose intrinsic quadrupole deformations are 0.474, 0.478, and −0.308, respectively. The corresponding RHB+PGCM densities are also included in the figure for comparison. It can be observed that the QMC+QCM densities are lower in the central region and larger at radial distances between approximately 1 and 2–3 fm. This behav… view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p014_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p015_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p016_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6 [PITH_FULL_IMAGE:figures/full_fig_p017_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7 [PITH_FULL_IMAGE:figures/full_fig_p018_7.png] view at source ↗
read the original abstract

We investigate anomalous large-angle scattering (ALAS) of $\alpha$-particles from $N=Z$ nuclei within the framework of the single-folding model. Differential cross sections are calculated by folding the $\alpha$-nucleon interaction with nuclear density distributions obtained from both relativistic and non-relativistic mean-field models. The folding procedure employs a Gaussian-form $\alpha$-nucleon interaction, with its energy dependence and range constrained by previous theoretical studies. Our results show that ALAS in $sd$-shell nuclei is reasonably well reproduced using the microscopic densities together with an $\alpha$-nucleon interaction characterized by a unified parameter set, in which only two parameters vary with the mass number.

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

2 major / 1 minor

Summary. The manuscript investigates anomalous large-angle α-scattering (ALAS) from N=Z sd-shell nuclei in a single-folding model. Microscopic densities from relativistic and non-relativistic mean-field calculations are folded with a Gaussian α-nucleon interaction whose energy dependence and range are constrained by prior work; the central claim is that ALAS is reasonably reproduced using a unified parameter set in which only two parameters vary with mass number A.

Significance. If the reproduction holds with the stated minimal parameter variation, the result would indicate that mean-field densities capture the essential physics of ALAS without explicit clustering, supporting single-folding models with microscopic inputs for large-angle alpha scattering across the sd-shell.

major comments (2)
  1. [Abstract] Abstract: the claim that ALAS 'is reasonably well reproduced' with only two mass-dependent parameters is load-bearing for the assertion that the microscopic densities drive the result. The manuscript provides no demonstration that a fully fixed (A-independent) parameter set still yields acceptable large-angle cross sections; without this test, the mass dependence may compensate for deficiencies in the mean-field densities (e.g., surface or clustering effects) rather than the densities themselves accounting for ALAS.
  2. [Abstract] Abstract and results discussion: no quantitative metrics (χ² values, specific angular ranges of agreement, or error estimates) are supplied to substantiate the 'reasonable' reproduction; this leaves the quality of the fit to visual inspection and makes it difficult to separate the contribution of the microscopic densities from the two adjustable parameters.
minor comments (1)
  1. Notation for the Gaussian α-N interaction parameters should be defined explicitly at first use to avoid ambiguity when discussing their mass dependence.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We appreciate the referee's thorough review and valuable feedback on our manuscript. The comments highlight important aspects regarding the robustness of our claims and the presentation of results. We address each major comment below and indicate the revisions we plan to make.

read point-by-point responses

  1. Referee: [Abstract] Abstract: the claim that ALAS 'is reasonably well reproduced' with only two mass-dependent parameters is load-bearing for the assertion that the microscopic densities drive the result. The manuscript provides no demonstration that a fully fixed (A-independent) parameter set still yields acceptable large-angle cross sections; without this test, the mass dependence may compensate for deficiencies in the mean-field densities (e.g., surface or clustering effects) rather than the densities themselves accounting for ALAS.

    Authors: We recognize that testing a completely A-independent parameter set would provide stronger evidence that the microscopic densities are responsible for reproducing ALAS. In our approach, the two varying parameters (the strength V0 and the range parameter) exhibit only mild dependence on A, as determined from fits to lighter nuclei in prior work. To address this, we will perform additional calculations in the revised manuscript using fixed parameters (e.g., those optimized for 16O) across the sd-shell nuclei and compare the results. This will demonstrate that the ALAS anomaly is primarily captured by the densities, with the weak A-dependence serving mainly for fine-tuning rather than compensating for deficiencies. revision: yes

  2. Referee: [Abstract] Abstract and results discussion: no quantitative metrics (χ² values, specific angular ranges of agreement, or error estimates) are supplied to substantiate the 'reasonable' reproduction; this leaves the quality of the fit to visual inspection and makes it difficult to separate the contribution of the microscopic densities from the two adjustable parameters.

    Authors: We agree that quantitative measures would enhance the objectivity of our claims. In the revised version, we will include χ² per degree of freedom for the large-angle scattering data (θ_cm > 90°), specify the angular ranges of good agreement, and provide estimates of uncertainties arising from the parameter choices and density variations. This will help quantify the reproduction quality and better isolate the contribution of the mean-field densities. revision: yes

Circularity Check

0 steps flagged

No significant circularity in the derivation chain

full rationale

The paper calculates differential cross sections by folding an α-nucleon Gaussian interaction (energy dependence and range taken from prior theoretical studies) with nuclear densities from independent relativistic and non-relativistic mean-field models. The central claim is that ALAS is reproduced when the interaction uses a unified parameter set in which only two parameters vary with mass number. No quoted equation or step reduces the output cross sections to the input densities or parameters by construction; the mass dependence is presented as a model feature rather than a fit renamed as prediction. No self-citation is invoked as the sole load-bearing justification for uniqueness or the ansatz, and the densities remain externally computed. The derivation is therefore self-contained against the stated inputs.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The model depends on mean-field calculated densities as input and a small number of fitted parameters in the interaction potential.

free parameters (1)
  • mass-dependent parameters in alpha-nucleon interaction
    Only two parameters vary with the mass number to achieve the reproduction of ALAS.
axioms (1)
  • domain assumption Gaussian form for the alpha-nucleon interaction with energy dependence and range from previous studies
    The folding procedure employs a Gaussian-form α-nucleon interaction, with its energy dependence and range constrained by previous theoretical studies.

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Reference graph

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