{"id":"2391c957-16f5-4141-b945-c6a8e61bfdc6","arxiv_id":"2607.01599","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":4.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Dispersive optical model analyses of 40Ca to 208Pb nuclei show neutron skin thickness rising stronger than linearly with asymmetry, consistent with GFMC He results and drip-line expectations.","lead":"The paper reports new dispersive optical model results for neutron skins in 54Fe and 90Zr plus updates for Ca and Pb isotopes, showing skins increase somewhat stronger than linearly with asymmetry (N-Z)/A. A smart generalist might read it to see how nuclear data could constrain neutron-star models.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.3","headline":"No significant objection identified","rationale":"The reader's identification of the DOM-to-ground-state mapping as the weakest link matches the argument structure. No stronger internal flaw (e.g., circularity in the trend fitting or unstated extrapolation) appears once the full text is considered; the low-confidence UNVERDICTED status is therefore appropriate pending external validation of the skins.","tokens_in":1621,"tokens_out":276,"duration_ms":15319,"concrete_test":"Re-fit the DOM potentials for 40Ca and 48Ca using the same elastic data but with an independent geometry constraint (e.g., fixed from electron scattering charge densities) and recompute the skins; if the sign for 40Ca or the slope of the (N-Z)/A trend reverses, the reported behavior is sensitive to model assumptions.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim constructs an asymmetry trend from DOM-derived skins (negative for 40Ca, rising for 48Ca/54Fe/90Zr/208Pb) and links it to GFMC He results. For this to hold, the extracted skins must be faithful to ground-state densities. The reader's weakest assumption correctly isolates this point; the full text does not introduce an additional internal inconsistency or unexamined assumption that would undermine the trend construction itself.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript reports new dispersive optical model (DOM) analyses of elastic scattering data for 54Fe and 90Zr, together with updated DOM results for 40Ca, 48Ca, and 208Pb. Neutron skins extracted from these fits are plotted versus asymmetry (N-Z)/A, revealing a trend that begins with a negative skin in 40Ca and rises somewhat more steeply than linearly; this trend is connected to Green's function Monte Carlo results for asymmetric helium isotopes and is argued to be consistent with expectations for very large skins near the neutron drip line, thereby motivating the identification of nuclei most relevant to neutron-star physics.","tokens_in":1704,"tokens_out":427,"duration_ms":23250,"significance":"If the extracted skins faithfully represent ground-state densities, the reported asymmetry trend supplies an empirical bridge between light and heavy nuclei that could constrain isovector properties of the nuclear force and the equation of state of neutron-rich matter. The explicit linkage to ab initio GFMC calculations for helium isotopes is a positive feature that allows a direct test of consistency across methods.","major_comments":[],"minor_comments":[{"comment":"The abstract and introduction do not quote the numerical skin values, their uncertainties, or the χ^{2} values of the underlying DOM fits; these quantities should be tabulated (e.g., in a new Table 1) so that the claimed trend can be verified quantitatively.","section":null},{"comment":"Section 3 (or equivalent) should include a direct comparison of the DOM skins with at least one independent extraction method (e.g., parity-violating electron scattering or ab initio calculations) for the same nuclei to substantiate the weakest assumption identified in the review.","section":null},{"comment":"The statement that the trend is 'somewhat stronger than linear' is not accompanied by a quantitative measure (slope, χ^{2} of linear vs. quadratic fit, or similar); adding such a metric would strengthen the claim.","section":null}],"recommendation":"minor_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the positive assessment of our manuscript, the recognition of its significance in bridging light and heavy nuclei, and the recommendation for minor revision. No specific major comments were raised in the report.","responses":[],"tokens_in":1168,"tokens_out":60,"duration_ms":15287,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main point is straightforward: new dispersive optical model analyses for 54Fe and 90Zr, plus updates for the calcium isotopes, produce a neutron-skin versus asymmetry plot that begins negative for 40Ca and rises somewhat steeper than linear, then links to the GFMC results on asymmetric helium. That combined trend is the concrete addition here.\n\nThe work stays inside the established DOM framework but supplies two fresh nuclei and assembles the full set into one figure. This gives a clearer empirical picture of how skin thickness grows with (N-Z)/A, which lines up with the expectation of large skins near the drip line. The motivation toward neutron-star radius constraints is stated plainly without overclaiming.\n\nThe soft spot is the usual one for this method: the skins come from optical-model fits to scattering data, so their accuracy depends on how faithfully those parameters capture the ground-state densities. The paper does not appear to add new cross-checks against other density functionals or ab initio calculations beyond the helium connection, which leaves the trend's robustness tied to the DOM assumptions. No obvious internal inconsistency shows up in the construction of the plot itself.\n\nThis is the kind of incremental but data-driven result that people tracking the symmetry energy will want to see. A reader working on empirical anchors for neutron-star models or planning rare-isotope experiments would find the asymmetry figure useful. I would send it to peer review; the central trend is falsifiable against the reported fits and adds specific points worth checking.","headline":"The paper adds DOM fits for 54Fe and 90Zr that extend an existing asymmetry trend for neutron skins, starting negative in 40Ca and rising to connect with GFMC helium results.","tokens_in":2175,"tokens_out":384,"would_cite":false,"duration_ms":17047,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Neutron skins in nuclei increase stronger than linearly with asymmetry starting from a negative value in calcium-40.","keywords":["neutron skin","dispersive optical model","nuclear asymmetry","neutron drip line","elastic scattering","neutron stars"],"falsifier":"A precise measurement of the neutron skin in 48Ca or 54Fe that falls well below the linear trend extrapolated from the DOM results would contradict the reported asymmetry dependence.","tokens_in":2535,"feed_emoji":"","tokens_out":625,"duration_ms":21203,"temperature":0.7,"pith_summary":"Dispersive optical model analyses of elastic scattering data are performed for 54Fe and 90Zr, with updated results for 40Ca, 48Ca, and 208Pb. The extracted neutron skins begin negative for 40Ca and rise somewhat more steeply than linearly when plotted against the asymmetry parameter (N-Z)/A. This pattern connects to Green's function Monte Carlo calculations for asymmetric helium nuclei and matches the expectation of very large skins in nuclei near the neutron drip line. The work therefore raises the question of which specific nuclei best bridge nuclear structure to neutron star physics.","feed_headline":"Neutron skins rise faster than linearly with asymmetry","feed_subtitle":"DOM analyses from calcium to lead link a negative skin in 40Ca to large skins near the drip line and neutron-star matter.","key_machinery":"Dispersive optical model fits to elastic scattering data that extract neutron skins as the difference between neutron and proton radii.","core_discovery":"Starting with a negative skin for 40Ca, a trend increasing somewhat stronger than linear emerges when the neutron skin of these nuclei is considered as a function of asymmetry, (N-Z)/A, and linked to the Green's function Monte Carlo results for asymmetric He nuclei. This general trend is consistent with the expectation that nuclei near the neutron drip line are expected to have very large neutron skins. The present analysis therefore motivates the question of which nuclei provide the most relevant link to neutron star physics.","pith_inferences":["If the steeper-than-linear trend holds, models of neutron-rich nuclei could be calibrated more tightly against a few key measurements rather than assuming strict linearity.","The same relation might be tested by extending DOM analyses to additional medium-mass nuclei with known scattering data.","A mismatch between this trend and ab-initio calculations for heavier systems would point to missing physics in the optical-model treatment of asymmetry."],"forward_implications":["Neutron skins become very large in nuclei approaching the neutron drip line.","The asymmetry dependence connects nuclear ground states to properties of neutron-rich matter.","Certain nuclei may serve as better experimental anchors for neutron-star equation-of-state constraints than others."],"fun_headline_variants":["Neutron skins rise superlinearly with asymmetry","40Ca negative skin starts superlinear asymmetry trend","Superlinear neutron skins from Ca to Pb nuclei","DOM shows superlinear neutron skin growth with asymmetry","Negative 40Ca skin links to drip-line neutron skins"],"cache_read_input_tokens":64,"weakest_assumption_plain":"The neutron skins extracted from the dispersive optical model fits to elastic scattering data accurately reflect the true ground-state neutron distributions in these nuclei.","fun_headline_variants_meta":{"raw":{"variants":["Neutron skins rise superlinearly with asymmetry","40Ca negative skin starts superlinear asymmetry trend","Superlinear neutron skins from Ca to Pb nuclei","DOM shows superlinear neutron skin growth with asymmetry","Negative 40Ca skin links to drip-line neutron skins"]},"model":"grok-4.3","cost_usd":0.004317,"raw_usage":{"total_tokens":2135,"prompt_tokens":601,"num_sources_used":0,"completion_tokens":71,"cost_in_usd_ticks":43174500,"prompt_tokens_details":{"text_tokens":601,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1463,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":601,"tokens_out":71,"duration_ms":17951,"temperature":1.0,"reasoning_tokens":1463,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-03T04:28:47.157571+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A precise measurement of the neutron skin in 48Ca or 54Fe that falls well below the linear trend extrapolated from the DOM results would contradict the reported asymmetry dependence.","supporting_citations":[],"review_version":1}