{"id":"c3838402-5cc8-4784-b13a-1c1448b25427","arxiv_id":"2501.12182","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":3.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"Inclusive photoproduction of J/psi mesons in proton-lead collisions at the LHC can likely be separated from hadronic background using centrality, rapidity-gap, and forward-neutron veto selections, extending the measurable transverse-momentum range to about 20 GeV.","lead":"This paper argues that the LHC can act as a photon-proton collider, letting physicists measure a particular type of J/psi particle production in proton-lead collisions. It uses simulations tuned to older data to show that a clear signal could be isolated from background in the CMS detector.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Centrality-association assumption: 80–100% CC retaining 100% of photoproduction is unsupported and likely energy/centrality-dependent, yet it drives all quoted signal yields and purities.","rationale":"The reader's verdict is CONDITIONAL and the weakest assumption cited by the reader is exactly the same: the 80–100% CC contains 100% of the photoproduction signal and only 6% of the hadroproduction background. I agree that this is the most load-bearing premise. The paper states it in Sec. 3 with no derivation, no uncertainty, and no MC cross-check in the present proceedings; it points to companion work [17]. The centrality class is defined by hadronic activity, and the mapping from impact parameter to centrality is not exact, so the 100% assumption is a genuine numerical premise, not just a loose approximation. The rest of the procedure (rapidity-gap cuts, ZDC veto) is well motivated; the paper is transparent that the MC is LO and tuned. These are acceptable for a feasibility study, but the centrality-fraction premise, if wrong, directly scales every quoted yield and the headline PT=20 GeV reach. The concrete test I propose uses only standard tools (Glauber + photon flux) and would settle the premise without new data; alternatively the derivation in the companion paper should be checked. Since the paper itself is a proceedings summary and the detailed derivation may exist in [17], the verdict should not be REJECT; it should remain CONDITIONAL, with the condition being that the 100% signal-in-80-100%-CC premise is verified quantitatively. The disagreement with consensus is not the issue; the issue is an unstated, numerically critical assumption. I therefore agree with the reader's identification and recommended verdict, and I do not see a separate more load-bearing concern.","tokens_in":6782,"tokens_out":1834,"duration_ms":17462,"concrete_test":"Reproduce the photoproduction centrality distribution using a standard Glauber model plus the photon flux: compute the fraction of Pb-going photons that produce a J/psi (with the HERA-tuned gamma-p cross section) as a function of the impact parameter, then map impact parameter to the 80–100% centrality class using the same Ncoll distribution (ALICE V0/forward-energy estimator) that defines the CC. If the resulting fraction of photoproduction events in the 80–100% CC is below ~90%, the paper's stated signal yields and 20 GeV reach are overstated. The same test in the companion paper [17] should be located; if it already contains this fraction or a measured constraint, the concern is resolved.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The paper's selection strategy hinges on the claim (Sec. 3) that the 80–100% centrality class contains 6% of hadroproduced J/psi and 100% of photoproduced J/psi, based on ALICE pPb data at 5.02 TeV [24]. This is the single quantity that sets the signal-to-background ratio after the centrality cut; if the true photoproduction fraction in the 80–100% CC is, say, 70% rather than 100%, all yields in Fig. 2 are overestimated by the same factor and the PT reach statements (up to 20 GeV) are not supported. The paper cites companion work [17] for the detailed derivation but does not reproduce the estimate or its uncertainties here. Physically, photoproduction is not strictly impact-parameter-saturated by the most peripheral bin: photon fluxes extend over all impact parameters, and the 80–100% CC is defined by hadronic activity (ZN or forward energy), which is only loosely correlated with impact parameter. ALICE measured the hadroproduction centrality dependence at 5.02 TeV, but applying that to photoproduction at 8.16 TeV requires an unstated model assumption. Additionally, the paper's own Fig. 1 shows the 80–100% CC still contains a substantial hadroproduction component, so the 100% signal assumption is not verified by the MC presented. The accompanying text does not provide any cross-check (e.g., a Glauber or impact-parameter distribution of the photon flux) for this premise.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper proposes a strategy to measure inclusive J/psi photoproduction in proton-lead collisions at sqrt(s_NN)=8.16 TeV with the CMS detector. The authors use HO+PYTHIA at LO in NRQCD, tune the photoproduction colour-singlet and colour-octet contributions to H1 data and the hadroproduction background to LHCb pp data, then extrapolate to pPb collisions. The proposed selection combines a peripheral (80--100%) centrality class, a pseudorapidity-gap requirement Delta_eta_gamma above a pT-dependent threshold, and a veto on forward neutrons from zero-degree calorimeters. The paper reports expected yields up to pT=20 GeV for an integrated luminosity of 1000 nb^-1 in Run 3+4, and argues that inclusive quarkonium photoproduction is thus accessible at the LHC, extending the kinematic reach beyond HERA.","tokens_in":7174,"tokens_out":3774,"duration_ms":41102,"significance":"If the central projections are correct, the paper would establish inclusive quarkonium photoproduction as a measurable LHC observable, providing a new dataset to constrain colour-octet matrix elements in NRQCD and complementing HERA measurements. The use of an existing LO event generator tuned to external H1 and LHCb data is a sensible and reproducible starting point, and the qualitative selection ingredients -- peripheral centrality, rapidity gaps, and forward-neutron veto -- are physically well motivated. The paper is also honest in referring to the companion work [17] for the detailed derivation. However, the quantitative reach claim (up to pT=20 GeV) rests on an unquantified and largely untested assumption about the photoproduction content of the 80--100% centrality class, which is the main fragility of the analysis.","major_comments":[{"comment":"The statement that the 80--100% centrality class contains 100% of the photoproduction signal and only 6% of the hadroproduction background is load-bearing for every yield in Fig. 2, yet it is not derived or assigned an uncertainty anywhere in the manuscript. The 6% hadroproduction fraction is taken from ALICE pPb data at 5.02 TeV [24], while the 100% photoproduction fraction is an assumption with no model support. The MC presented in the paper does not validate it: Fig. 1 shows the 80--100% centrality class still contains a substantial hadroproduction component, and no centrality-selected photoproduction sample is shown. Photon fluxes extend over all impact parameters, and the 80--100% class is defined by hadronic activity, which is only loosely correlated with impact parameter in pPb. Please either derive the photoproduction fraction using a Glauber/impact-parameter model with the photon flux, or present a sensitivity scan (e.g., signal fraction 70%, 85%, 100%) and show how the yields and the pT=20 GeV reach in Fig. 2 change. Without this, the quoted signal-to-background ratio and the central feasibility claim are not quantitatively supported.","section":"Sec. 3"},{"comment":"The tuning and extrapolation procedure is described only qualitatively, which makes the central projection difficult to assess. The tune factors for the photoproduction (3S1[1], 1S0[8]) and hadroproduction (3S1[1], 3S8[1]) contributions are not tabulated; the fit ranges, chi^2 values, and uncertainties are not given; and the implementation of the A-scaling and N_coll folding is not specified. Since the claimed high-pT reach depends on the shape of the photoproduction pT spectrum and on the background shape after all selection cuts, the reader cannot judge whether the extrapolation from H1 and LHCb data to pPb at 8.16 TeV is reliable. This is also a self-identified limitation: the paper directs the reader to the companion work [17] for details. Please include at least a table of the tuned parameters and a visual comparison of the tuned HO+PYTHIA predictions with the H1 and LHCb data points used, or explicitly state that such details are deferred to [17] and restrict the quantitative claims accordingly.","section":"Sec. 2"}],"minor_comments":[{"comment":"The definition of Delta_eta_gamma states that both the charged-track acceptance and the calorimeter acceptance have 'eta_cal < 2.5, pT_cal > 0.4 GeV'; these must be different acceptances in practice. Please clarify the exact pseudorapidity and pT thresholds for the track and calorimeter selections, since the rapidity-gap definition is a central part of the proposed selection.","section":"Sec. 3"},{"comment":"The text says that Delta_eta_gamma^stat min is chosen to 'minimise the statistical uncertainty of the sample in the selection region', but the precise minimised quantity is not defined. Please state the criterion (e.g., relative statistical uncertainty, significance) and how the per-pT thresholds shown in Fig. 2 are computed.","section":"Sec. 3 and Fig. 2"},{"comment":"There are minor typographical issues: 'psuedorapidities' should be 'pseudorapidities', and 'de-exciation' should be 'de-excitation'. Also, the notation 'O( 0.01%)' is unusual; consider writing 'of order 0.01%'.","section":"Sec. 3"}],"recommendation":"major_revision","confidential_remarks":"This is a proceedings-style paper that explicitly presents a condensed version of the companion study [17]. The main technical details of the tuning, the MC comparison, and the uncertainty treatment are in [17]; the standalone manuscript therefore asks the reader to take several load-bearing claims on faith. The referee report focuses on what can be assessed from the present text, and the centrality-association assumption is the key risk. If the authors can provide a quantitative derivation or a sensitivity scan for that assumption, the paper would be suitable for publication; otherwise, the central feasibility claim is not supported beyond the qualitative level."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Kate, you should know upfront: this is a proceedings summary, not a full paper. The author says so herself by pointing to [17] for the detailed study of ALICE, ATLAS, and LHCb. The new bit here is the CMS-focused projection, but I don't see any derivation or selection numbers that aren't already in [17] (or at least are not shown here). So judge it as a conference write-up of a bigger project.\n\nWhat's good: the MC strategy is sensible and transparent. Tuning HELAC-Onia+PYTHIA to H1 and LHCb data, then extrapolating to pPb, is a reasonable way to get a first handle on yields. The selection logic—peripheral centrality to suppress hadroproduction, rapidity gaps to further separate, ZDC veto for photonuclear background—is physically motivated and clearly described. The paper also correctly labels the tune uncertainties as bands and doesn't oversell the precision. For a proceedings, it's a neat illustration.\n\nThe soft spot is the one the stress-test flags. The claim that the 80–100% centrality class contains 100% of photoproduction while keeping 6% of hadroproduction is load-bearing, and it's not derived here. It's inferred from ALICE pPb data at 5.02 TeV, and applying it to 8.16 TeV without a Glauber or impact-parameter check is a stretch. If that fraction is 70% instead of 100%, every yield in Fig. 2 shifts down by that factor and the PT=20 GeV reach statement weakens. The paper does not give a contingency or a sensitivity scan. That's a real gap for a standalone claim.\n\nAlso, the extrapolation from pp to pPb uses a simple A scaling and N_coll folding. That's okay as a first approximation, but nuclear modifications to the gluon PDF or to the hadronization could change the background shape. The paper doesn't discuss those.\n\nMy read: the underlying idea is plausible and the companion paper [17] likely carries the actual substance. As a proceedings citation, it's fine. If someone submits this as a journal paper, a referee would rightly ask for details on the centrality assumption and tune uncertainties. For this version, I would not send it to peer review; the proper target is the detailed study.","headline":"A clear proceedings summary of a plausible CMS projection, but the 100% photoproduction-in-peripheral-centrality assumption is unquantified and load-bearing.","tokens_in":7674,"tokens_out":3786,"would_cite":false,"duration_ms":37105,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":false},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"Inclusive J/psi photoproduction in proton-lead collisions at the LHC can be isolated from the hadronic background and measured up to transverse momentum of 20 GeV.","keywords":["inclusive quarkonium photoproduction","ultra-peripheral collisions","J/psi production","proton-lead collisions","CMS","rapidity gaps","centrality selection","NRQCD"],"falsifier":"A dedicated measurement of the centrality distribution of inclusive J/psi production in pPb collisions at 8.16 TeV would settle the question: if a significant fraction of photoproduction events appear in more central classes because the photon-induced system produces extra particles that shift the centrality estimator, the 80-100% selection would not retain all of the signal, and the predicted yields and purity would drop.","tokens_in":6553,"feed_emoji":"⚛️","tokens_out":15145,"duration_ms":119268,"temperature":0.7,"pith_summary":"The paper argues that inclusive photoproduction of J/psi mesons—a process for which HERA data are statistically limited—can be measured at the LHC in proton-lead collisions at $\\sqrt$(s_NN)=8.16 TeV. By selecting the 80-100% peripheral centrality class, requiring a rapidity gap between the J/psi and all other detected particles, and vetoing forward neutrons, the hadroproduction background can be suppressed by about 94% while retaining the full photoproduction signal. Using projected Run3+4 luminosity of 1000 $nb^{-1}$, the paper predicts measurable yields in the CMS detector up to transverse momentum PT=20 GeV, twice the reach of the HERA dataset. If correct, this would turn the LHC into a photon-hadron collider for inclusive studies and sharpen tests of quarkonium production mechanisms, particularly the colour-octet contribution.","feed_headline":"Inclusive J/psi photoproduction at LHC is measurable to PT=20 GeV","feed_subtitle":"Centrality and rapidity-gap cuts remove 94% of background, doubling the reach of HERA data","key_machinery":"The central mechanism is the event-selection strategy built on three observables: the centrality class restricted to 80-100%, which exploits the absence of hadronic activity in photoproduction; the rapidity gap $\\Delta\\eta_\\gamma$, defined as the minimum pseudorapidity distance from the $J/\\psi$ to any other particle in the detector, which separates photon-induced from hadronic final states; and the forward-neutron veto using zero-degree calorimeters, which rejects broken lead ions. The quantitative predictions rest on two Monte Carlo tunes with HELAC-Onia+PYTHIA at leading order in NRQCD (non-relativistic QCD): the colour-singlet $^3S_1^{[1]}$ and colour-octet $^1S_0^{[8]}$ contributions are tuned to H1 photoproduction data for the signal, while the $^3S_1^{[1]}$ and $^3S_1^{[8]}$ contributions are tuned to LHCb data for the hadroproduction background, scaled by the number of nucleon-nucleon collisions from ALICE.","core_discovery":"The central claim is that inclusive J/psi photoproduction, where a quasi-real photon from the lead ion breaks up the proton, can be cleanly separated from the much larger hadroproduction background in the CMS detector. The separation is achieved with three selection criteria: restricting to the most peripheral centrality class (80-100%), which is expected to contain all photoproduction events and only 6% of hadroproduction events; requiring a rapidity gap Delta_eta_gamma above a PT-dependent threshold chosen to minimise the statistical uncertainty; and vetoing forward neutron activity in the zero-degree calorimeters, which removes residual hadronic collisions with negligible loss of signal. Using leading-order NRQCD Monte Carlo tuned to H1 photoproduction data for the signal and to LHCb pp data for the background, the paper predicts that with 1000 $nb^{-1}$ of Run3+4 data the photoproduced J/psi signal is observable in the CMS acceptance up to PT=20 GeV, with O(10) events in the 16-20 GeV bin in the central rapidity region.","pith_inferences":["The assumption that the 80-100% centrality class holds all photoproduction events could be tested on existing Run-2 pPb data at 8.16 TeV before Run3+4, since CMS has already recorded such collisions.","If the leading-order NRQCD tune underestimates the colour-octet contribution at high PT, the photoproduction signal near PT=20 GeV could be larger than predicted, improving the measurement prospects but altering the expected background-to-signal ratio.","The same centrality-plus-gap selection could be extended to other inclusive photon-induced final states, such as Upsilon production or open heavy flavour, generalising the LHC as a photon-hadron collider for inclusive studies."],"forward_implications":["The LHC can produce an inclusive quarkonium photoproduction dataset with PT reach up to 20 GeV, twice the HERA reach, using 1000 nb^-1 of Run3+4 pPb data in CMS.","The 80-100% centrality selection removes 94% of the hadroproduction background while retaining the full photoproduction signal.","A no-neutron veto in the zero-degree calorimeters rejects essentially no photoproduction signal, with a neutron-emission probability of order 0.01%.","The rapidity-gap requirement Delta_eta_gamma > Delta_eta_stat_min_gamma, optimised per PT bin, suppresses the background enough that about 10 signal events are expected in the 16-20 GeV bin in the central rapidity region.","The same selection strategy can be applied in ATLAS and, qualitatively, in ALICE and LHCb, enabling multi-experiment inclusive photoproduction studies."],"supporting_citations":[{"why":"H1 photoproduction data used to tune the colour-singlet and colour-octet contributions to the simulated photoproduction signal.","marker":"[12–14]"},{"why":"LHCb pp J/psi production cross-sections at 5 TeV used to tune the hadroproduction background Monte Carlo.","marker":"[10]"},{"why":"Provides the b-hadron feed-down subtraction applied to the H1 data before the photoproduction signal is tuned.","marker":"[23]"},{"why":"ALICE centrality-dependent J/psi measurement in p-Pb at 5.02 TeV that supplies the 6% hadroproduction fraction in the 80-100% centrality class and the N_coll distribution for folding the background.","marker":"[24]"},{"why":"Estimates of forward-neutron emission in photoproduction that justify the high signal efficiency of the no-neutron veto.","marker":"[25, 26]"}],"fun_headline_variants":["J/psi photoproduction at LHC reachable to 20 GeV","LHC photon-proton collisions expose J/psi to 20 GeV","Photoproduced J/psi detectable at LHC to PT=20 GeV","94% background cut reveals J/psi photoproduction to 20 GeV","Photon-proton J/psi yield measurable at LHC up to 20 GeV"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The central assumption is that the most peripheral 80-100% centrality class contains all photoproduction events while holding only 6% of hadroproduction events, a fraction borrowed from ALICE data at 5.02 TeV rather than established for 8.16 TeV proton-lead collisions.","fun_headline_variants_meta":{"raw":{"variants":["J/psi photoproduction at LHC reachable to 20 GeV","LHC photon-proton collisions expose J/psi to 20 GeV","Photoproduced J/psi detectable at LHC to PT=20 GeV","94% background cut reveals J/psi photoproduction to 20 GeV","Photon-proton J/psi yield measurable at LHC up to 20 GeV"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001032,"raw_usage":{"total_tokens":4316,"prompt_tokens":887,"completion_tokens":3429,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":503,"completion_tokens_details":{"reasoning_tokens":3327}},"tokens_in":503,"tokens_out":3429,"duration_ms":24722,"temperature":1.0,"reasoning_tokens":3327,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-10T17:25:19.111406+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A dedicated measurement of the centrality distribution of inclusive J/psi production in pPb collisions at 8.16 TeV would settle the question: if a significant fraction of photoproduction events appear in more central classes because the photon-induced system produces extra particles that shift the centrality estimator, the 80-100% selection would not retain all of the signal, and the predicted yields and purity would drop.","supporting_citations":[{"cited_title":"Measurement of𝐽/𝜓 production cross-sections in𝑝𝑝 collisions at√𝑠= 5 TeV,","cited_arxiv_id":null,"evidence_quote":"LHCb pp J/psi production cross-sections at 5 TeV used to tune the hadroproduction background Monte Carlo."}],"review_version":1}