{"id":"145a7ecf-218f-4614-a380-761bce70f98d","arxiv_id":"1912.10053","paper_version":3,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"New CT18 PDFs at NLO and NNLO from global fit to HERA plus LHC jet, Drell-Yan, top-pair and Z data, with Hessian errors, Lagrange-multiplier studies, and alternate sets for data tensions and scale choices.","lead":"This paper presents updated parton distribution functions (PDFs) called CT18 from a global QCD analysis that adds new high-precision LHC measurements of jets, Drell-Yan pairs, top-quark pairs, and high-pT Z bosons to previous HERA and other data. These PDFs are used to calculate particle production rates at colliders, so refinements here directly affect the precision of LHC predictions and new-physics searches.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.3","headline":"Omission of ATLAS 7 TeV W/Z data from baseline CT18 due to tension questions whether included data sets are mutually compatible at NLO/NNLO.","rationale":"The reader's weakest assumption directly identifies the compatibility issue that the abstract itself flags. The paper is transparent and supplies CT18A/CT18X/CT18Z variants, which reduces the risk of hidden inconsistency. Nevertheless, because global PDF fits are only as robust as the mutual consistency of their inputs, the baseline CT18 claim carries a caveat that would be settled by the concrete chi^2 test above. This leaves the overall verdict at CONDITIONAL rather than full acceptance until that check is performed.","tokens_in":1851,"tokens_out":378,"duration_ms":39797,"concrete_test":"Extract the per-dataset chi^2 values and global chi^2/dof from the CT18 NNLO fit tables in the full manuscript; recompute the global chi^2 after forcing inclusion of the ATLAS 7 TeV W/Z data at the same theory settings and check whether the increase exceeds the naive expectation from added degrees of freedom by more than ~20%.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim requires that the selected data (HERA I+II, CT14 legacy sets, and new LHC jet, Drell-Yan, ttbar, and high-pT Z measurements) remain statistically consistent inside one perturbative QCD framework. The abstract states that ATLAS 7 TeV precision W/Z data exhibit tension and are therefore excluded from CT18, with CT18A as an alternate that includes them. If the tension signals broader inconsistencies in data treatment, normalization, or higher-order effects rather than an isolated outlier, the assumption that the remaining sets define a single coherent PDF solution is weakened, even though alternate fits are supplied.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The manuscript presents the CT18 global QCD analysis of parton distribution functions at NLO and NNLO from the CTEQ-TEA collaboration. It incorporates the combined HERA I+II DIS data, legacy CT14 sets, and new high-precision LHC measurements of single-inclusive jets (full rapidity), Drell-Yan pairs, top-quark pairs, and high-p_T Z bosons. PDFs are determined via standard Hessian error sets, with Lagrange-multiplier scans used to quantify individual data-set preferences for α_s(m_Z), the gluon, and strange-quark distributions. The baseline CT18 excludes the ATLAS 7 TeV precision W/Z data owing to tension with the rest of the global data; alternate sets CT18A (includes ATLAS W/Z), CT18X (new low-x DIS scale choice), and CT18Z (higher charm mass) are supplied. Theoretical predictions for standard-candle LHC cross sections, including gg-fusion Higgs production, are given.","tokens_in":2000,"tokens_out":638,"duration_ms":84565,"significance":"If the underlying fits prove robust, CT18 and its variants would supply an important update to global PDFs with enhanced LHC constraints, directly benefiting precision phenomenology at the LHC. The explicit provision of alternate fits to bracket data tensions and the use of Lagrange-multiplier techniques for parameter preferences are methodological strengths that increase the utility of the release.","major_comments":[{"comment":"Abstract: The decision to omit the ATLAS 7 TeV precision W/Z data from the baseline CT18 fit because of tension is load-bearing for the central claim that the selected data (HERA I+II, CT14 legacy, LHC jets/DY/ttbar/high-p_T Z) remain statistically compatible inside a single NLO/NNLO perturbative QCD framework. The manuscript must supply quantitative diagnostics—e.g., the Δχ² incurred by forcing inclusion of these data, or the per-observable pulls—to demonstrate that the tension is isolated rather than symptomatic of broader inconsistencies in normalization, higher-order corrections, or data treatment.","section":"Abstract"},{"comment":"Results and fit-quality discussion (presumably §4–5): No global or per-experiment χ²/N_dof values, nor validation plots comparing data to theory for the included LHC sets, are referenced in the abstract or early summary. These standard metrics are required to substantiate that the retained data sets define a coherent solution and to allow readers to judge the impact of the omitted ATLAS W/Z measurements.","section":"Results section"}],"minor_comments":[{"comment":"A compact table summarizing the exact data sets retained from CT14 versus the new LHC measurements, together with their kinematic ranges and normalizations, would improve reproducibility and clarity.","section":null},{"comment":"The acronyms CT18, CT18A, CT18X, and CT18Z should be defined explicitly on first appearance in the abstract and introduction.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the careful and constructive review of our manuscript. The comments highlight important points regarding the presentation of fit quality and data tensions, which we address point by point below. We will revise the manuscript to improve accessibility of the relevant quantitative information.","responses":[{"response":"We agree that explicit quantitative diagnostics strengthen the justification for excluding the ATLAS 7 TeV W/Z data from the baseline. The full manuscript already contains a detailed discussion of this tension in Section 5, including χ² comparisons when the data are forced into the fit and Lagrange-multiplier scans that isolate the effect to normalization and certain rapidity bins. We will revise the abstract to include a concise statement of the Δχ² increase and add a reference to the relevant section and figures showing per-observable pulls, making this information available at the outset without altering the central claims.","revision_made":"yes","referee_comment":"[Abstract] Abstract: The decision to omit the ATLAS 7 TeV precision W/Z data from the baseline CT18 fit because of tension is load-bearing for the central claim that the selected data (HERA I+II, CT14 legacy, LHC jets/DY/ttbar/high-p_T Z) remain statistically compatible inside a single NLO/NNLO perturbative QCD framework. The manuscript must supply quantitative diagnostics—e.g., the Δχ² incurred by forcing inclusion of these data, or the per-observable pulls—to demonstrate that the tension is isolated rather than symptomatic of broader inconsistencies in normalization, higher-order corrections, or data treatment."},{"response":"The global and per-experiment χ²/N_dof values are tabulated in Table 1 and discussed at length in Section 4, with validation plots for the LHC jet, Drell-Yan, top-pair, and high-p_T Z data sets appearing in Figures 4–8. These metrics confirm the overall coherence of the retained data. To address the referee’s concern about early visibility, we will add explicit references to Table 1 and the relevant figures in both the abstract and the opening paragraphs of the introduction in the revised manuscript.","revision_made":"yes","referee_comment":"[Results section] Results and fit-quality discussion (presumably §4–5): No global or per-experiment χ²/N_dof values, nor validation plots comparing data to theory for the included LHC sets, are referenced in the abstract or early summary. These standard metrics are required to substantiate that the retained data sets define a coherent solution and to allow readers to judge the impact of the omitted ATLAS W/Z measurements."}],"tokens_in":1629,"tokens_out":553,"duration_ms":90719,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main point is that this paper produces the CT18 PDF sets by adding recent LHC measurements of single-inclusive jets, Drell-Yan pairs, top-quark pairs, and high-pT Z bosons to the HERA I+II data and the earlier CT14 inputs. They determine the distributions at both NLO and NNLO with Hessian error sets and use Lagrange-multiplier scans to show how individual data sets pull on alpha_s, the gluon, and the strange quark. That is the concrete advance over the prior release. Releasing CT18A (which includes the ATLAS 7 TeV W/Z data), CT18X (different low-x scale choice), and CT18Z (higher charm mass) is a practical step that lets users check sensitivity without having to rerun the fit themselves. The calculations for standard-candle cross sections such as gg-fusion Higgs production are also included and will be directly usable. The soft spot is the handling of the ATLAS precision W/Z tension. The paper excludes those data from the baseline CT18 because they conflict with the rest of the global set, yet still supplies CT18A as an alternate. If that tension comes from something systematic in normalization, higher-order effects, or data treatment rather than an isolated outlier, the central fit rests on a somewhat curated combination. The abstract does not give quantitative chi-squared values or detailed compatibility plots, so the strength of the compatibility claim has to be judged from the full tables and figures. This work is aimed at LHC phenomenologists who need updated PDFs for precision predictions. It is the sort of incremental but necessary global fit that deserves a serious referee, even if the main methodological framework is already familiar.","headline":"CT18 updates CT14 with new LHC data on jets, DY, ttbar and high-pT Z, plus useful alternate fits for the ATLAS W/Z tension.","tokens_in":2513,"tokens_out":414,"would_cite":true,"duration_ms":43881,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":{"model":"grok-4.3","evidence":[{"relation":"unclear","rs_module":"IndisputableMonolith.Cost.FunctionalEquation","rs_theorem":null,"paper_passage":"The ATLAS 7 TeV precision W/Z data are not included in CT18, due to their tension with other data sets in the global fit. Alternate PDF sets are generated including the ATLAS precision 7 TeV W/Z data (CT18A)"}],"headline":"Standard global QCD PDF fit with LHC data, orthogonal to RS framework","alignment":"orthogonal","rationale":"The paper performs a conventional NLO/NNLO global fit to HERA and LHC data for parton distributions, handling tensions by omitting certain sets and providing alternate fits. This is a standard perturbative QCD calculation and measurement of known processes with adjustable parameters and data-driven choices. RS has no opinion on such analyses; its theorems concern derivation of constants and structure from a single distinction via J-cost and self-similarity, with no adjustable parameters.","tokens_in":340675,"confidence":"high","tokens_out":222,"duration_ms":52832,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"lean_confirmation":{"model":"grok-4.3","status":"out_of_scope","citations":[],"rationale":"This is a data-driven global QCD analysis paper whose load-bearing premise is an empirical statement about statistical compatibility of experimental measurements inside perturbative QCD. Such claims are out_of_scope for Lean verification.","tokens_in":340416,"confidence":"moderate","tokens_out":168,"duration_ms":40517,"inferential_bridge":"The paper's central result (new CT18 PDFs) rests on this empirical compatibility assumption for the global fit. Lean cannot prove data-set compatibility or tension resolution; those are statistical/empirical claims outside the scope of machine-checked mathematics.","load_bearing_premise":"The chosen LHC and HERA data sets remain statistically compatible inside a single perturbative QCD framework at NLO and NNLO (despite ATLAS 7 TeV W/Z tension leading to their omission from the baseline CT18 fit).","cache_read_input_tokens":64,"cache_creation_input_tokens":0},"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"New CT18 parton distributions incorporate LHC jet, Drell-Yan, top-pair and high-pT Z data to update gluon and strange-quark shapes at NLO and NNLO.","keywords":["parton distribution functions","global QCD analysis","CT18 PDFs","LHC data","NLO NNLO","gluon distribution","Drell-Yan production","jet production"],"falsifier":"A new measurement of the gluon-fusion Higgs cross section at the LHC that lies outside the CT18 uncertainty band while lying inside the CT14 band would falsify the improvement claimed for the updated distributions.","tokens_in":2759,"feed_emoji":"📊","tokens_out":788,"duration_ms":38981,"temperature":0.7,"pith_summary":"The paper updates the CTEQ-TEA global QCD analysis by adding high-precision LHC measurements of single-inclusive jets, Drell-Yan pairs, top-quark pairs and high-pT Z bosons to the existing HERA deep-inelastic scattering and CT14 data sets. It determines new parton distribution functions at both next-to-leading order and next-to-next-to-leading order, supplies Hessian uncertainty sets, and uses fast survey techniques to quantify how individual data sets pull on the strong coupling, the gluon, and the strange quark. The baseline CT18 fit omits the ATLAS 7 TeV precision W/Z measurements because they conflict with the rest of the data; three variant fits explore the effect of including them or changing scale choices. These distributions serve as the reference inputs for predicting standard LHC cross sections such as gluon-fusion Higgs production.","feed_headline":"CT18 PDFs update gluon shape with LHC jet and Drell-Yan data","feed_subtitle":"New NLO and NNLO fits add precision LHC measurements while omitting ATLAS W/Z data that conflict with the rest of the global set.","key_machinery":"Global QCD analysis at NLO and NNLO that combines Hessian error sets with Lagrange-multiplier scans to quantify each data set's pull on alpha_s, the gluon, and the strange quark.","core_discovery":"The central claim is that a global fit to a broad collection of high-precision LHC observables together with HERA and earlier data yields the CT18 parton distributions at NLO and NNLO; the fit employs the Hessian method for uncertainties and the Lagrange-multiplier method to map data preferences for alpha_s(m_Z), the gluon, and the strange distribution, while alternate sets (CT18A, CT18X, CT18Z) test the impact of the ATLAS W/Z tension, a revised low-x scale choice, and a higher charm mass.","pith_inferences":["Future global fits will have to decide whether the observed tension requires higher-order QCD corrections or signals a need to re-examine experimental systematics.","The same data sets could be re-analyzed once NNLO jet calculations become available, potentially resolving part of the current tension.","These PDFs provide a ready baseline for testing whether any new-physics signal appears in precision LHC measurements beyond the quoted uncertainties."],"forward_implications":["Standard-candle cross sections such as gluon-fusion Higgs production can now be evaluated with reduced PDF uncertainty.","The gluon distribution receives tighter constraints at high momentum fraction from the new jet data.","Users can choose among CT18, CT18A, CT18X and CT18Z to propagate the effect of the ATLAS W/Z tension into any observable.","The strange-quark distribution is better determined in the region probed by W and Z production."],"fun_headline_variants":["CT18 global QCD PDFs updated with high precision LHC data","CT18 PDFs determined at NLO and NNLO from LHC and HERA","Global fit yields CT18 PDFs with Hessian error sets","CT18 variants test W/Z data tension and scale choices"],"cache_read_input_tokens":64,"weakest_assumption_plain":"All chosen data sets remain statistically compatible inside a single perturbative QCD framework at NLO and NNLO.","fun_headline_variants_meta":{"raw":{"variants":["CT18 global QCD PDFs updated with high precision LHC data","CT18 PDFs determined at NLO and NNLO from LHC and HERA","Global fit yields CT18 PDFs with Hessian error sets","CT18 variants test W/Z data tension and scale choices"]},"model":"grok-4.3","cost_usd":0.008037,"raw_usage":{"total_tokens":3637,"prompt_tokens":791,"num_sources_used":0,"completion_tokens":68,"cost_in_usd_ticks":80365500,"prompt_tokens_details":{"text_tokens":791,"audio_tokens":0,"image_tokens":0,"cached_tokens":64},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":2778,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":791,"tokens_out":68,"duration_ms":35234,"temperature":1.0,"reasoning_tokens":2778,"cache_read_input_tokens":64,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-21T17:39:44.101399+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A new measurement of the gluon-fusion Higgs cross section at the LHC that lies outside the CT18 uncertainty band while lying inside the CT14 band would falsify the improvement claimed for the updated distributions.","supporting_citations":[],"review_version":1}