{"id":"91b92db1-a5cb-4075-a3a3-3ffd89da95c8","arxiv_id":"2411.12187","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":7.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"The Pom-CQM model of J/psi photoproduction on the nucleon is extended to predict exclusive J/psi photoproduction cross sections on deuteron, helium-4, oxygen-16, and calcium-40, with relativistic deuteron wave functions and final-state interactions.","lead":"This paper predicts how often a photon turns into a J/psi particle when it hits a nucleus, for targets from the deuteron up to calcium-40. These predictions give experimentalists concrete cross sections to look for at JLab and the future Electron-Ion Collider, and they show that measuring near threshold can probe the deuteron's d-state and final-state interactions.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"FSA-validity test omits the d-state that drives the physics, so the claim that FSA is good at higher energies is not yet established.","rationale":"The paper is a good-faith phenomenological study: the deuteron impulse term is computed with realistic NN wavefunctions, and the d-state sensitivity follows naturally from the deuteron form factors, so that part of the central claim is solid. The load-bearing soft spot is the validation of the FSA itself: Fig. 10 checks FSA only after removing the d-state, even though the d-state is the component the paper identifies as dominant near threshold and the one with more high-momentum strength. Since the FSA error comes from freezing p=0 inside the γN amplitude, an s-wave-only test can easily understate the error for the full amplitude. The same FSA is then used in the FSI loop and for A>2 predictions, so the gap is not confined to a diagnostic plot. The reader's stated weakest assumption (the fitted FSI t-matrix and mixed relativistic/nonrelativistic propagators) is a real but secondary concern; the more direct issue is that the FSA-validity claim is tested on a truncated wavefunction. This does not require rejecting the paper, but it does require a conditional acceptance with a specific numerical check, which is compatible with the existing CONDITIONAL verdict.","tokens_in":20308,"tokens_out":21811,"duration_ms":268204,"concrete_test":"Reproduce Fig. 10 at Eγ = 6, 8, and 10 GeV using the full s+d deuteron wave function and the FSA form factor Fave(t) of Eq. (40), comparing with the exact relativistic impulse calculation of Eq. (24) (the solid curves of Fig. 7). Quantify the ratio FSA/full in the dominant -t range. If the ratio stays within about 20-30% at Eγ = 8 and 10 GeV, the higher-energy FSA claim is supported; if not, the conclusion in Sec. VI and the FSA-based FSI/A>2 predictions need a corrective caveat or a more accurate treatment.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section IV.B concludes that the fixed-scatter approximation is 'a good approximation at higher energies' on the basis of Fig. 10, which deliberately keeps only the s-wave part of the deuteron. FSA freezes the initial nucleon momentum to p=0 inside t_VN (Eqs. 34/39), while the exact impulse amplitude Eq. (24) integrates over p. The d-state, which Fig. 9 shows dominates the cross section near threshold, has substantially more high-momentum content than the s-state (Fig. 14), so the p=0 error is not representative of the full amplitude. The paper never compares FSA with the exact full s+d calculation. The same untested FSA is then used in the FSI source term (Eq. 41) and in the A>2 predictions (Eq. 52), so the unvalidated part of the approximation propagates into the FSI and heavy-nucleus results. This does not threaten the d-state sensitivity finding itself, but it does undermine the companion claim that FSA is reliable at higher energies and the numerical predictions built on it.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"Applying the Pom-CQM model previously fitted to γp→J/ψp JLab data, the authors compute exclusive J/ψ photoproduction on the deuteron, 4He, 16O, and 40Ca within multiple scattering theory. The deuteron impulse amplitude is calculated exactly from realistic NN wave functions with relativistic boost corrections, a fixed-scatter approximation (FSA) is introduced, and the J/ψ-nucleus final-state interaction is generated from a first-order optical potential built from the same J/ψN amplitude. Heavy-nucleus predictions use variational Monte Carlo form factors. The main claims are that near-threshold cross sections depend strongly on the deuteron d-state, that the FSA fails near threshold but is a good approximation at higher energies, that FSI effects are significant at large momentum transfer, and that the A>2 cross sections provide predictions for future JLab and EIC experiments.","tokens_in":20559,"tokens_out":5751,"duration_ms":58615,"significance":"If the results hold, the paper provides concrete, falsifiable predictions for a program that is experimentally active, and it identifies deuteron d-state sensitivity as a potentially observable nuclear-structure effect in J/ψ photoproduction. The strengths are the exact impulse treatment on the deuteron with realistic NN potentials, the comparison across three NN interactions, the use of VMC nuclear form factors for heavier targets, and the honest reuse of a proton-level amplitude that was previously fitted to data. The central d-state-sensitivity finding near threshold appears robust because it is obtained from the exact impulse calculation. However, the FSA-validity claim is supported only by an s-wave-only comparison, and the FSI calculation relies on that same unvalidated approximation, so the higher-energy FSA claim and the numerical FSI predictions need additional support.","major_comments":[{"comment":"The conclusion that the FSA is \"a good approximation at higher energies\" is based on a comparison in which only the s-wave part of the deuteron is retained. Near threshold the d-state dominates the cross section (Fig. 9), and the d-state has more high-momentum content than the s-state (Fig. 14), so freezing the initial nucleon momentum to p=0 in Eq. (34) is not tested for the full amplitude. Please compare the FSA of Eqs. (38)-(40) with the exact impulse calculation of Eq. (24) using the full s+d wave function, or restrict the FSA-validity claim to the s-wave sector and re-evaluate the FSA-based FSI and A>2 predictions.","section":"IV.B, Fig. 10"},{"comment":"The FSI amplitude uses the T_IMP source term evaluated in the FSA by setting the initial nucleon momentum to p=0, as stated after Eq. (48). The comparison in Fig. 11 therefore mixes the exact relativistic impulse calculation (dashed curve) with a calculation in which the FSI source term is approximated by the FSA (solid curve). Since the FSA is shown to be invalid near threshold, the displayed FSI enhancement cannot be cleanly attributed to final-state interactions alone, and the near-threshold FSI predictions are not reliable. Please use the exact impulse amplitude as the source term in Eq. (41), or quantify the FSA error in the FSI contribution.","section":"IV.C, Eqs. (41)-(51) and Fig. 11"},{"comment":"The J/ψ-deuteron scattering equation uses a nonrelativistic propagator E - E_V(p\") - E_d(p\"), while the impulse amplitude and the boost transformations use relativistic kinematics (Eqs. (28)-(33)). Given that the FSI is significant near threshold where the momentum transfer is large, the magnitude of the FSI correction may depend on this inconsistency. Please justify this choice or estimate its numerical effect, for example by comparing with a relativistic propagator.","section":"IV.C, Eq. (45)"}],"minor_comments":[{"comment":"The symbol t is used both for the Mandelstam variable and for a momentum-transfer variable in the same sentence; the displayed relation \"t = (|q| − E_V(k))^2 − t^2\" is self-referential and should be rewritten with distinct notation for the three-momentum transfer.","section":"Eq. (34)"},{"comment":"There are several typographical errors that should be corrected: \"Relatvistic\" in Sec. IV.A, \"calulated\" near Eq. (46), \"gennerated\" in the Fig. 14 caption, \"variaioal\" in Sec. VI, \"previsous\" in Sec. V, and \"sufficent\" in the Fig. 3 caption.","section":"Throughout"},{"comment":"The legend order in panel (a) reads \"2H p 16O 40Ca 4He,\" which does not match the plotted curves or the order in panel (b); please check that the legend and curve styles are consistent.","section":"Fig. 15"},{"comment":"The text says the full FSA cross section is obtained by using Eq. (39) to evaluate T_IMP inside Eq. (41), but Eq. (39) defines the factorized FSA amplitude for the observable cross section rather than an operator to be inserted into the loop integral; clarifying the operator definition would remove ambiguity.","section":"Eq. (51)"}],"recommendation":"major_revision","confidential_remarks":"This is a useful nuclear-physics application of the authors' previously fitted Pom-CQM model. The central d-state-sensitivity result is credible and likely robust, but the abstract and Sec. VI state that the FSA is a good approximation at higher energies on the basis of an s-wave-only test, and the same untested FSA enters the FSI and heavy-nucleus predictions. A revision that adds a full s+d FSA comparison and either uses the exact impulse source in the FSI or quantifies the error would make the paper's claims match its evidence."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Read this for the deuteron impulse calculation, not for the heavy-nucleus numbers. The paper does something concrete: it computes the exact impulse amplitude for γd → J/ψd using realistic NN wave functions, adds a relativistic boost treatment, and shows that near threshold the cross section is dominated by the d-state and that the result is an order of magnitude larger than the nonrelativistic one. That is a real, falsifiable prediction for JLab or EIC kinematics. The comparison of three NN potentials (AV18, NV-IIa, CD-Bonn) gives a sense of the wave-function uncertainty, and the paper states its limitation for sub-threshold physics clearly.\n\nThe soft spot is the FSA validation. The paper concludes that the fixed-scatter approximation is 'a good approximation at higher energies' based on Fig. 10, but that figure only compares FSA with the exact calculation keeping the s-wave part of the deuteron. The d-state, which the paper itself shows dominates near threshold and has more high-momentum content, is excluded from the test. So the claim that FSA is reliable at higher energies is not actually established for the full amplitude. This matters because the same FSA is then used in the FSI source term and in the A>2 predictions. The d-state sensitivity result does not depend on this, and the paper is transparent about using s-wave for the test, but the conclusion overreaches the calculation actually shown.\n\nA second, smaller concern is the mixed relativistic treatment: the impulse term is boosted, while the FSI uses a nonrelativistic V-d propagator (Eq. 45) with FSA. The authors mention consistency but the numerical size of this inconsistency is not estimated. Inherited uncertainty from the fitted proton amplitude is acknowledged by reusing the fit, but not propagated. These are the kind of caveats one expects in a phenomenological multiple-scattering paper; they do not invalidate the core deuteron result.\n\nI would send this to a referee. The deuteron part is a legitimate new calculation, the paper is honest about its regime of validity, and the heavy-nucleus predictions give the experimental community numbers to aim at, even if the FSA caveat should be sharpened in revision.","headline":"Worth engaging for the deuteron d-state result; the FSA reliability claim needs a stronger test before it is used for A>2.","tokens_in":21126,"tokens_out":2787,"would_cite":true,"duration_ms":25136,"reading_group":"yes","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Applying a Pomeron-plus-constituent-quark model to exclusive J/psi photoproduction on nuclei, this paper predicts that near threshold the deuteron cross section is governed by the d-state of the deuteron wave function, while the standard…","keywords":["J/psi photoproduction","exclusive reactions on nuclei","multiple scattering theory","fixed scatter approximation","deuteron d-state","Pomeron constituent quark model","nuclear form factors","final state interactions"],"falsifier":"A measurement of $d\\sigma/dt$ for $\\gamma d \\to J/\\psi d$ near $E_\\gamma = 6$ GeV in the region $-t \\approx 2$ to $4$ GeV$^2$ would settle the central claim: the full calculation including the d-state is much larger than the s-wave-only result in that region, so data matching the s-wave-only shape, or failing to show the expected enhancement, would refute the claimed d-state dominance.","tokens_in":20072,"feed_emoji":"⚛️","tokens_out":7848,"duration_ms":76188,"temperature":0.7,"pith_summary":"The paper predicts exclusive $J/\\psi$ photoproduction cross sections on the deuteron, $^{4}$He, $^{16}$O, and $^{40}$Ca by extending a Pomeron-plus-constituent-quark model of the proton reaction to nuclear targets. For the deuteron, where the impulse amplitude can be computed exactly from realistic nucleon-nucleon wave functions, the central finding is that near threshold the cross section is strongly sensitive to the d-state, the $L=2$ component of the deuteron wave function, and the conventional fixed-scatter approximation, which factorizes the amplitude into a nucleon amplitude times a nuclear form factor, is not valid in that region but becomes reliable at higher energies. The $J/\\psi$-nucleus final state interaction, built from the first-order optical potential, contributes mainly at large momentum transfer. With the fixed-scatter approximation and variational Monte-Carlo form factors, the paper provides cross-section predictions for $^{4}$He, $^{16}$O, and $^{40}$Ca intended for upcoming JLab and EIC measurements. A sympathetic reader would take this as a step toward using $J/\\psi$ photoproduction to probe gluonic and short-distance structure in nuclei.","feed_headline":"Near threshold, deuteron d-state drives J/psi yields","feed_subtitle":"Exact deuteron calculation shows the fixed-scatter approximation fails near threshold, guiding JLab and EIC runs","key_machinery":"The central object is the multiple-scattering decomposition of the reaction amplitude into an impulse term $T^{\\rm IMP}_{J/\\psi A,\\gamma A}$ and a final-state-interaction term $T^{\\rm FSI}_{J/\\psi A,\\gamma A}$. For the deuteron, the impulse amplitude is computed exactly from realistic nucleon-nucleon wave functions with relativistic boost transformations, and it is this exact treatment that exposes the d-state sensitivity. The final-state interaction is built from a first-order optical potential formed by folding the $J/\\psi$-nucleon scattering amplitude from the Pom-CQM model with the nuclear form factor, with a Lippmann-Schwinger equation solved for the $J/\\psi$-nucleus scattering amplitude. The fixed-scatter approximation, which sets the struck nucleon momentum to zero and factorizes the amplitude as a nucleon amplitude times a nuclear form factor, is the simplifying device used for $A > 2$ nuclei; the paper tests its validity on the deuteron and finds that it fails near threshold.","core_discovery":"On the paper's own terms, exclusive $J/\\psi$ photoproduction on the deuteron near threshold is strongly controlled by the d-state of the deuteron wave function. Using the relativistic impulse amplitude built from the Argonne-v18, NV-IIa, and CD-Bonn nucleon-nucleon potentials, the calculations show that at $E_\\gamma = 6$ GeV, about 0.4 GeV above threshold, the differential cross section at large $-t$ is much larger than the s-wave-only result, tracing to the quadrupole form factor $F_2(t)$ peaking where $F_0(t)$ has its minimum. The same comparison shows that the fixed-scatter approximation, which factorizes the nuclear amplitude into an averaged nucleon amplitude times a form factor, reproduces the exact calculation only at small $-t$ and fails near threshold. The final state interaction amplitude, evaluated from a first-order optical potential using the fitted $J/\\psi$-nucleon amplitude, raises the cross section significantly at large $-t$. The paper then applies the fixed-scatter approximation to spin-zero nuclei, predicting cross sections for $^{4}$He, $^{16}$O, and $^{40}$Ca with variational Monte-Carlo form factors, and notes that these near-threshold predictions are not reliable in the subthreshold region where hidden-charm bound states could appear.","pith_inferences":["If the d-state sensitivity holds, exclusive $J/\\psi$ photoproduction on the deuteron could serve as a high-momentum filter for the deuteron quadrupole form factor $F_2(t)$, complementing electron-scattering measurements in the momentum region where $F_0(t)$ has a minimum; this use goes beyond what the paper states.","The failure of the fixed-scatter approximation near threshold suggests that similar fixed-scatter treatments for other heavy-quarkonium photoproduction, such as $\\Upsilon$ on light nuclei, would also need exact many-body impulse calculations because the threshold momentum transfer is even larger.","Precise coherent deuteron data could be used to extract the $J/\\psi$-nucleon scattering amplitude entering the optical potential, connecting these predictions to the hidden-charm bound-state question that the paper flags as an open direction.","Because the paper explicitly states its subthreshold predictions are unreliable under the fixed-scatter approximation, a natural next step is a full many-body calculation with realistic nuclear wave functions and all multiple-scattering permutations, which could be tested against the near- and sub-threshold nuclear data now being collected at JLab."],"forward_implications":["Near-threshold $\\gamma d \\to J/\\psi d$ measurements can directly probe the deuteron d-state at high momentum transfer, since the s-wave-only calculation is substantially smaller in the large-$-t$ region at $E_\\gamma = 6$ GeV.","The fixed-scatter approximation should not be trusted for threshold-region $J/\\psi$ photoproduction on any nuclear target, and the paper's own $A > 2$ predictions are correspondingly approximate in that region.","The $J/\\psi$-nucleus final state interaction significantly increases cross sections at large momentum transfer for the deuteron and for the spin-zero nuclei near threshold.","For $^{4}$He, $^{16}$O, and $^{40}$Ca, the predicted near-threshold cross sections are very small, while heavier targets give larger total cross sections at higher energy, so future JLab and EIC measurements are more feasible at higher energies.","The predicted cross sections for $^{4}$He, $^{16}$O, and $^{40}$Ca provide concrete numbers for planning exclusive measurements at JLab and the EIC."],"supporting_citations":[{"why":"Bases the nucleon-level picture: it introduces the Pom-CQM model of $\\gamma N \\to J/\\psi N$ whose amplitudes are extended to nuclear targets in this paper.","marker":"[1]"},{"why":"Supplies the fitted fit1 parameters of the quark-nucleon potentials, including $\\alpha_B$, $\\alpha_{\\rm FSI}$, $\\mu_B$, $\\mu_{\\rm FSI}$, $N_B$, and $N_{\\rm FSI}$, that define the Born and final-state-interaction amplitudes used throughout.","marker":"[11]"},{"why":"Provides the JLab proton near-threshold data that determine the low-energy dynamical part of the fitted model and serve as the baseline for the nuclear predictions.","marker":"[2–4]"},{"why":"Establishes the multiple-scattering theory and distorted-wave impulse approximation underlying the $T^{\\rm IMP} + T^{\\rm FSI}$ decomposition and the first-order optical potential.","marker":"[21–25]"},{"why":"Demonstrates the earlier application of the same fixed-scatter approximation to $\\phi$ photoproduction on $^{4}$He, the formulation that the present paper extends to $J/\\psi$ on heavier nuclei.","marker":"[26]"},{"why":"Generates the realistic deuteron wave functions from the Argonne-v18, NV-IIa, and CD-Bonn potentials whose s-wave and d-wave components are compared in the exact impulse calculation.","marker":"[41–43]"},{"why":"Provides the instant-form relativistic treatment used to boost the deuteron wave function in the exact impulse amplitude.","marker":"[44–48]"},{"why":"Supplies the variational Monte-Carlo ground-state wave functions and nuclear form factors for $^{4}$He, $^{16}$O, and $^{40}$Ca used in the fixed-scatter approximation predictions.","marker":"[52]"},{"why":"Motivates probing short-range nuclear structure through subthreshold $J/\\psi$ and $\\Upsilon$ production in $\\gamma A$ collisions, which this paper takes as context.","marker":"[28]"}],"fun_headline_variants":["Deuteron d-state controls near-threshold J/psi photoproduction","Fixed-scatter approximation fails for near-threshold J/psi","Exact deuteron wave function shifts J/psi cross sections","J/psi photoproduction near threshold hinges on deuteron d-state","d-state effect dominates J/psi yields near threshold"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"All results inherit the fitted Pom-CQM quark-nucleon potentials that were tuned to proton JLab data, so the entire nuclear calculation, especially the final-state interaction, stands on the assumption that the resulting $J/\\psi$-nucleon amplitude remains correct for nucleons bound inside a nucleus.","fun_headline_variants_meta":{"raw":{"variants":["Deuteron d-state controls near-threshold J/psi photoproduction","Fixed-scatter approximation fails for near-threshold J/psi","Exact deuteron wave function shifts J/psi cross sections","J/psi photoproduction near threshold hinges on deuteron d-state","d-state effect dominates J/psi yields near threshold"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000299,"raw_usage":{"total_tokens":1853,"prompt_tokens":1191,"completion_tokens":662,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":807,"completion_tokens_details":{"reasoning_tokens":587}},"tokens_in":807,"tokens_out":662,"duration_ms":6789,"temperature":1.0,"reasoning_tokens":587,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-12T17:48:26.345307+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A measurement of $d\\sigma/dt$ for $\\gamma d \\to J/\\psi d$ near $E_\\gamma = 6$ GeV in the region $-t \\approx 2$ to $4$ GeV$^2$ would settle the central claim: the full calculation including the d-state is much larger than the s-wave-only result in that region, so data matching the s-wave-only shape, or failing to show the expected enhancement, would refute the claimed d-state dominance.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Bases the nucleon-level picture: it introduces the Pom-CQM model of $\\gamma N \\to J/\\psi N$ whose amplitudes are extended to nuclear targets in this paper."},{"cited_title":"Duran et al., Determining the gluonic gravitational form factors of the proton, Nature 615, 813 (2023)","cited_arxiv_id":null,"evidence_quote":"Supplies the fitted fit1 parameters of the quark-nucleon potentials, including $\\alpha_B$, $\\alpha_{\\rm FSI}$, $\\mu_B$, $\\mu_{\\rm FSI}$, $N_B$, and $N_{\\rm FSI}$, that define the Born and final-state-interaction amplitudes used throughout."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Demonstrates the earlier application of the same fixed-scatter approximation to $\\phi$ photoproduction on $^{4}$He, the formulation that the present paper extends to $J/\\psi$ on heavier nuclei."},{"cited_title":"Witala, J","cited_arxiv_id":null,"evidence_quote":"Supplies the variational Monte-Carlo ground-state wave functions and nuclear form factors for $^{4}$He, $^{16}$O, and $^{40}$Ca used in the fixed-scatter approximation predictions."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Motivates probing short-range nuclear structure through subthreshold $J/\\psi$ and $\\Upsilon$ production in $\\gamma A$ collisions, which this paper takes as context."}],"review_version":1}