{"id":"5a3e95e8-8f68-434e-9b87-8efd2e11b322","arxiv_id":"2009.14158","paper_version":2,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":6,"one_line_summary":"A dipole-model calculation with potential-model wave functions yields differential cross sections for exclusive quarkonia photoproduction, matching HERA J/psi data and predicting LHC nuclear rates.","lead":"This paper calculates how exclusive quarkonium particles are produced in ultraperipheral collisions as a function of momentum transfer squared, using two dipole models and potential-model wave functions. It reports that the BK model matches the HERA proton data for J/psi and provides predictions for LHC nuclear collisions.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Angle-correlation neglect in Eq. (2.9) is dismissed without a test and directly controls the t-slope on which the central claim rests.","rationale":"The reader's verdict is CONDITIONAL, and I do not see grounds to change it. The calculation is transparent, uses an external BK solution, and explicitly compares with H1 and LHC data, including the failures at small |t| for ALICE/CMS and the exclusion of other dipole models. Those admissions support rather than undermine the claim. The remaining risk is not the choice of potential (five potentials give similar results) or the nuclear formalism (t-shape dominated by nuclear form factor), but the input b-dependence of the dipole amplitude for the proton. In particular, the paper's only justification for neglecting r-b angular correlations is a qualitative sentence in Sec. VI citing Ref. [72]; since the phase factors in Eq. (2.9) depend on Δ, this correlation is not averaged away and can change the t-slope. That is directly load-bearing for the headline claim. The proposed test using the angle-dependent amplitude of Ref. [72] would settle it. I also note the post hoc selection of BK and bSat from seven models and the missing uncertainty bands; these weaken the strength of 'reproduce well' but are already captured by a conditional verdict.","tokens_in":18392,"tokens_out":12395,"duration_ms":129005,"concrete_test":"Recompute the γp→J/ψ dσ/dt at W=55 and 100 GeV for the Buchmuller-Tye wave function using an angle-dependent dipole amplitude with the cos²(φ_r−φ_b) correlation as in Ref. [72], instead of the angle-averaged N. Compare the resulting |t|-slope and χ² to the H1 data in Figs. 1 and 5. If the slope shifts by more than the H1 point-to-point errors or χ² degrades appreciably, the paper's t-dependence claim is not robust; if it shifts negligibly, the dismissal is justified.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The t-dependence in Eq. (2.9) is obtained from a Fourier transform over b of N(x,r,b). Both dipole amplitudes used—the bSat model (3.1) and the BK solution (3.3)–(3.4)—depend only on |r| and |b|, not on the angle between r and b. The paper explicitly acknowledges the angle-correlated amplitude of Ref. [72] (Sec. VI) but dismisses it as 'expected to not make a significant impact' because of angular integration. That dismissal is not quantitatively tested. In the amplitude, the phases e^{-ib·Δ} and e^{i(1-z)r·Δ} carry the external vector Δ, so the angular average is not an unweighted average over φ: a cos²(φ_r−φ_b) term in N survives the b integral and enters the r integral through J_2(rΔ) moments. It can therefore modify the t-slope, which is precisely the quantity the paper advertises. Since the H1 comparison in Figs. 1 and 5 is the main support for the setup, an untested assumption that directly shapes the t-slope is the weakest load-bearing link. In addition, the two models shown were selected from seven tested models based on the same H1 data, and no uncertainty bands from this selection are given.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents a dipole-picture calculation of the momentum-transfer-squared differential cross sections for exclusive quarkonia photoproduction on proton and nuclear targets, for J/psi, psi(2S), Upsilon(1S), and Upsilon(2S). The light-front quarkonium wave functions are obtained from five interquark potential models with Melosh spin rotation, and the scattering amplitudes are built from three b-dependent dipole amplitudes: the bSat model, a numerical solution of the BK equation with a collinearly improved kernel taken from Ref. [19], and the GBW model for nuclear targets. The authors validate the proton-target setup against H1 J/psi data at W = 55 and 100 GeV, compare pPb Upsilon production with CMS data and gamma-Pb J/psi production with ALICE data, and provide new predictions for coherent PbPb photoproduction at sqrt(s) = 5.02 TeV and y = 0. The central claim is that the Buchmuller-Tye potential combined with the b-dependent BK solution reproduces the H1 differential J/psi photoproduction data, and that the same setup yields t-dependent predictions for excited states and nuclear targets.","tokens_in":18723,"tokens_out":7663,"duration_ms":78864,"significance":"If the central claim holds, the paper provides a useful phenomenological framework for t-differential exclusive quarkonia photoproduction, combining realistic potential-model wave functions with state-of-the-art b-dependent saturation amplitudes. Its main strengths are that the BK amplitude is an external input not fitted to the t-differential J/psi data, that the framework gives first predictions for excited charmonia and bottomonia in gamma-A and AA UPCs, and that it confronts several data sets (H1, ALICE, CMS) within one formalism. The paper also explicitly identifies remaining model uncertainties, for example the difference between the BK and bSat results and the underestimation of small-transverse-momentum ALICE and CMS data. The significance is moderate: it is a phenomenological study rather than a precision extraction, and the most novel predictions for nuclei are not yet backed by high-statistics data.","major_comments":[{"comment":"The dismissal of the angle-dependent dipole amplitude of Ref. [72] is not quantitatively supported. In Eq. (2.9) the external momentum transfer enters through the phase e^{-i[b-(1-z)r]·Delta}, so if N(x,r,b) contains a term depending on the angle between r and b, the b and r angular integrals do not factor; a cos^2(phi_r - phi_b) correlation term survives the b integral and enters as J_2 moments in the r integral, which can modify the t-slope. Since the t-slope is the central advertised observable, the statement that the effect is expected to be insignificant should be backed by a numerical test, for example by repeating the gamma-p calculation with the amplitude of Ref. [72] over the displayed |t| range, or by estimating the size of the J_2 contribution.","section":"Sec. VI and Eq. (2.9)"},{"comment":"The paper reports that seven impact-parameter dependent dipole models were tested and that the two best were selected based on the same H1 J/psi data that are later used as the validation. This introduces a selection effect: the agreement of the BK and bSat curves with H1 data in Figs. 1, 3, and 5 is not an independent test of the framework. Please show the rejected models in at least the proton J/psi comparison, or provide an uncertainty band reflecting the spread of the seven models, so that the reader can judge how much of the agreement is due to model selection.","section":"Sec. III and Figs. 1-5"},{"comment":"The nuclear amplitude combines the Glauber-Gribov average in Eq. (5.3), which already resums multiple dipole-nucleon scatterings, with an additional multiplicative EPPS16 gluon-shadowing factor R_G in Eq. (5.10). This prescription may double-count the same shadowing physics, and the text gives no comparison with a calculation that omits R_G or applies it differently. Since the nuclear t-distributions in Figs. 7-9 are among the main new predictions, please justify this factorization and show the sensitivity of the nuclear results to the treatment of R_G.","section":"Sec. V, Eqs. (5.3) and (5.10)"}],"minor_comments":[{"comment":"The variable x appearing in the amplitude and dipole amplitudes is not defined explicitly in the text; please state the relation between x, W, M_V, and t used in the numerical calculation.","section":"Eq. (2.4)"},{"comment":"The caption contains a duplicated article: 'found with the the bSat dipole model'.","section":"Fig. 3 caption"},{"comment":"There is a typo in 'photoproducion' in the discussion of the ALICE data.","section":"Sec. VI"},{"comment":"The statement that the |t|-slope is 'close to a constant due to an almost exponential impact parameter profile' is qualitative; a log-linear plot of the predicted cross sections would make this statement quantitative and facilitate comparison with the H1 data.","section":"Sec. IV"},{"comment":"The notation A_{T,L} is potentially confusing for real photon photoproduction, where only the transverse overlap contributes; consider renaming the amplitude to make this explicit.","section":"Eq. (2.9)"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a solid phenomenological contribution and the main claims are defensible, but the two most important issues are (i) the untested neglect of r-b angular correlations, which directly affects the t-slope, and (ii) the model-selection effect in the H1 validation. Both are addressable within the paper's scope, so I recommend major revision rather than rejection. The nuclear shadowing treatment should also be clarified to avoid a possible double-counting concern."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"You should know this is a solid phenomenological dipole-model paper, not a breakthrough. It gives t-differential predictions for quarkonia photoproduction off protons and nuclei, using potential-model light-front wave functions for excited states (psi(2S), Upsilon(1S), Upsilon(2S)) and a b-dependent BK solution from Bendova et al. as an external input. The genuinely new pieces are the combination of the Buchmuller-Tye potential with Melosh rotation for excited states and the use of that b-dependent BK solution. The paper cites a closely similar boosted-Gaussian calculation [46], so the novelty is incremental, but the wave functions here are more realistic for excited states.\n\nThe H1 comparison for J/psi with the BK model is credible: the BK solution is not fitted to the t-differential cross section, so this is an independent check. The paper is honest about the bSat overshoot at small |t| and about the ALICE and CMS underestimation at small transverse momentum. The nuclear predictions are clearly labeled as predictions, and the Glauber-Gribov plus EPPS16 treatment is standard.\n\nThe main soft spot is the untested angle-correlation assumption. In Eq. (2.9) the t-dependence comes from a Fourier transform over b with the phase e^{-i[b-(1-z)r]·Delta}. The BK and bSat amplitudes depend only on |r| and |b|. The paper dismisses the angle-dependent amplitude of Ref. [72] as unimportant without a quantitative test. That dismissal is not self-evident: an angular correlation like cos^2(theta) can leave a J_2(rDelta) imprint, which alters the t-slope. Since the H1 comparison is the main validation, this deserves a robustness check, but it does not falsify the central result—the BK prediction is what it is, and it matches H1. A second soft spot is the selection of two from seven dipole models based on the same H1 data, with no uncertainty band from that selection. The bSat comparison is partially circular because its slope B_G came from HERA exclusive fits, but the BK comparison is not. Minor: no uncertainty bands on the nuclear predictions beyond the three dipole models.\n\nWho is this for? People working on UPC quarkonia phenomenology at the LHC or EIC. It is a useful reference for model comparisons, not a discovery. It deserves a serious referee; the referee should ask for a test of the angular-correlation assumption and for uncertainty estimates from model selection. I would send it to peer review.","headline":"A standard but useful dipole-model calculation: the BK comparison with H1 J/psi data is genuine, the excited-state potential-model wave functions are a real addition, and the main caveats are untested angular correlations and post-hoc model selection.","tokens_in":19242,"tokens_out":2527,"would_cite":true,"duration_ms":23599,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"pith_extraction":{"msc":[],"pacs":["14.40.Pq","13.60.Le","13.60.-r"],"model":"deepseek-v4-flash","headline":"A dipole model that combines potential-model quarkonium wave functions with an impact-parameter-dependent BK solution reproduces the measured t-dependence of exclusive J/psi photoproduction and predicts the same observable for heavier…","keywords":["quarkonium photoproduction","ultraperipheral collisions","dipole picture","Balitsky-Kovchegov equation","impact-parameter dependence","momentum transfer squared","potential model wave functions","gluon saturation"],"falsifier":"Measure dsigma/dt for psi(2S), Upsilon(1S), and Upsilon(2S) photoproduction on protons at W around 55-120 GeV and compare the slopes and normalizations with the BK-plus-Buchmuller-Tye predictions shown in the paper. If the excited-state slopes deviate systematically while the J/psi slope matches, the assumed b-profile, or its assumed independence of the angle between r and b, is falsified. The same test applies to the predicted coherent-dip positions in gamma-Pb collisions at $\\sqrt$(s)=5.02 TeV, where the destructive-interference minima at |t| around 0.02-0.06 $GeV^{2}$ provide a sharp signature of the nuclear implementation.","tokens_in":18195,"feed_emoji":"⚛️","tokens_out":7875,"duration_ms":65032,"temperature":0.7,"pith_summary":"Exclusive quarkonium photoproduction, where a quasi-real photon turns into a J/psi, psi(2S), Upsilon(1S), or Upsilon(2S) while the target stays intact, is one of the cleanest ways to image the transverse distribution of gluons inside a proton or nucleus. This paper argues that the full momentum-transfer-squared (t) dependence of such processes can be computed in the dipole picture, using quarkonium wave functions from a potential model (with Melosh spin rotation) and an impact-parameter-dependent dipole amplitude taken from the Balitsky-Kovchegov equation. With the Buchmuller-Tye potential and the b-dependent BK solution, the computed differential cross sections reproduce the H1 data for J/psi photoproduction on protons at W=55 and 100 GeV. The same setup yields t-dependent predictions for the excited psi and Upsilon states, and, through a Glauber-Gribov treatment with gluon shadowing, for coherent photoproduction off lead nuclei in gamma-A and A-A ultraperipheral collisions at sqrt(s)=5.02 TeV.","feed_headline":"Same dipole setup reproduces J/psi t-slopes and predicts all quarkonia","feed_subtitle":"The BK-based model that matches HERA's J/psi data also yields t-spectra for psi(2S), Upsilon(1S), Upsilon(2S), and lead-nucleus targets.","key_machinery":"The central object is the b-dependent dipole amplitude N(x,r,b), the imaginary part of the quark-antiquark dipole scattering amplitude at impact parameter b. The differential cross section is obtained from its Fourier transform over b, specifically from the amplitude integral $d^{2}$ b e^{-i[b-(1-z)r] . $\\Delta$} N(x,r,b) that appears in Eq. (2.9), so the b-profile of the dipole amplitude directly sets the |t|-slope. Two inputs for N are used: the bSat saturation model, which employs a Gaussian proton shape function T(b), and the numerical solution of the BK equation with the collinearly improved kernel from Ref. [19], which avoids unphysical Coulomb tails. The quarkonium wave functions come from solving the Schrodinger equation for five interquark potentials (power-like, harmonic oscillator, Cornell, Buchmuller-Tye, logarithmic) and boosting them to the infinite-momentum frame with the Melosh spin rotation, which substantially enhances excited-state production.","core_discovery":"The central claim is that the differential cross section dsigma/dt of exclusive quarkonia photoproduction, whose t-dependence is the Fourier conjugate of the impact-parameter profile of the target's gluon density, is reliably computable in the dipole picture provided the dipole amplitude depends on the impact parameter and the vector-meson wave functions are realistic. The paper shows that combining the Buchmuller-Tye interquark potential, used for the light-front wave functions including the Melosh spin transformation, with the numerical b-dependent solution of the Balitsky-Kovchegov equation with a collinearly improved kernel reproduces the H1 differential J/psi photoproduction data on the proton. The same setup provides t-dependent predictions for psi(2S), Upsilon(1S) and Upsilon(2S) on the proton and, via a Glauber-Gribov average over the nuclear thickness function together with an EPPS16-based gluon-shadowing factor, for coherent gamma-Pb to V-Pb and Pb-Pb to V-Pb-Pb at sqrt(s)=5.02 TeV. The authors emphasize that this is the first calculation combining a realistic potential-model treatment of excited-state wave functions with the latest b-dependent BK solution, and they use the alternative bSat model as a benchmark to expose the spread of model predictions.","pith_inferences":["If the BK-plus-Buchmuller-Tye description survives confrontation with future differential data, the slope of dsigma/dt becomes a direct, quantitative measurement of the gluon's impact-parameter profile at low x, effectively a transverse image of the nucleon at scales currently probed only indirectly.","A target-dependent preference (bSat for nuclei, BK for protons) suggests the b- and angle-dependence of the dipole amplitude is not universal, and implementing an r-b angular correlation is the natural next test of the framework.","The predicted Upsilon(2S)-to-Upsilon(1S) ratio could serve as a wave-function-sensitive discriminant among interquark potentials, turning exclusive photoproduction into a probe of quarkonium spectroscopy at the LHC or a future electron-ion collider.","Because the nuclear calculation embeds a proton dipole amplitude in a Glauber-Gribov average, a mismatch at the predicted dip positions in Pb-Pb data would point specifically to new nuclear effects beyond EPPS16 shadowing rather than to the proton b-profile."],"forward_implications":["The H1 differential J/psi photoproduction data are reproduced by the BK-plus-Buchmuller-Tye setup at W=55 and 100 GeV, establishing the b-dependent BK dipole amplitude as a viable input for t-dependent observables on the proton.","The same setup yields concrete t-dependent predictions for psi(2S), Upsilon(1S), and Upsilon(2S) photoproduction on protons at W=55-120 GeV, with the spread from five interquark potentials giving a theory band.","For ultraperipheral lead-lead and photon-lead collisions at sqrt(s)=5.02 TeV and central rapidity, the framework predicts coherent differential cross sections for all four quarkonia states, with destructive-interference dips appearing at nearly the same |t| for the psi and Upsilon families.","The comparison with ALICE and CMS data shows that the bSat model gives a closer description of the nuclear and p-Pb data, whereas the BK model is the one that matches the HERA proton data, so the preferred b-profile may depend on the target."],"supporting_citations":[{"why":"Provides the numerical b-dependent solution of the BK equation with the collinearly improved kernel that supplies the central dipole amplitude used in the main predictions.","marker":"[19]"},{"why":"Defines the impact-parameter dipole saturation (bSat) model with its Gaussian proton shape function, used as the benchmark dipole model throughout the paper.","marker":"[15]"},{"why":"Supplies the Buchmuller-Tye interquark potential used for the quarkonium light-front wave functions in the central results.","marker":"[38]"},{"why":"Provides the H1 differential J/psi photoproduction data at W=100 GeV that the BK-plus-Buchmuller-Tye calculation reproduces.","marker":"[53]"},{"why":"Provides the H1 differential J/psi photoproduction data at W=55 GeV used as the second comparison point for the proton-target results.","marker":"[54]"},{"why":"Establishes the authors' potential-model approach for quarkonium wave functions with Melosh spin rotation that the present calculation extends to t-dependent observables.","marker":"[33]"},{"why":"Supplies the EPPS16 nuclear parton distributions used to parametrize gluon shadowing for the nuclear-target photoproduction predictions.","marker":"[66]"},{"why":"Provides the ALICE differential J/psi photoproduction data in Pb-Pb UPCs used to test the nuclear-target predictions.","marker":"[12]"},{"why":"Provides the CMS p-Pb Upsilon(nS) photoproduction data used to compare the proton-target framework against transverse-momentum measurements.","marker":"[14]"}],"fun_headline_variants":["Dipole model matches HERA J/psi, predicts Upsilon and nuclear t-slopes","First full t-spectra for quarkonia in UPCs from realistic dipole model","Exclusive quarkonia t-spectra predicted by dipole model verified at HERA","Dipole model fits HERA J/psi, forecasts Upsilon and heavy-ion t-spectra"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The calculation's t-dependence is controlled entirely by the assumed impact-parameter profile of the dipole amplitude, N(x,r,b); if that profile is inaccurate, the Fourier transform yields the wrong slope of dsigma/dt even when the forward cross section is correct, and all proton and nuclear predictions inherit the error.","fun_headline_variants_meta":{"raw":{"variants":["Dipole model matches HERA J/psi, predicts Upsilon and nuclear t-slopes","First full t-spectra for quarkonia in UPCs from realistic dipole model","Exclusive quarkonia t-spectra predicted by dipole model verified at HERA","Dipole model fits HERA J/psi, forecasts Upsilon and heavy-ion t-spectra"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001238,"raw_usage":{"total_tokens":5136,"prompt_tokens":1056,"completion_tokens":4080,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":672,"completion_tokens_details":{"reasoning_tokens":3990}},"tokens_in":672,"tokens_out":4080,"duration_ms":24773,"temperature":1.0,"reasoning_tokens":3990,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-27T21:43:08.546276+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measure dsigma/dt for psi(2S), Upsilon(1S), and Upsilon(2S) photoproduction on protons at W around 55-120 GeV and compare the slopes and normalizations with the BK-plus-Buchmuller-Tye predictions shown in the paper. If the excited-state slopes deviate systematically while the J/psi slope matches, the assumed b-profile, or its assumed independence of the angle between r and b, is falsified. The same test applies to the predicted coherent-dip positions in gamma-Pb collisions at $\\sqrt$(s)=5.02 TeV, where the destructive-interference minima at |t| around 0.02-0.06 $GeV^{2}$ provide a sharp signature of the nuclear implementation.","supporting_citations":[],"review_version":1}