{"id":"f2f452ec-641e-4c7e-9036-bfc2dcc2f26c","arxiv_id":"2607.10638","paper_version":2,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":6.5,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"First simultaneous double-differential measurement of pionless CC muon-neutrino cross sections on carbon and oxygen versus kinematic imbalance observables with T2K ND280.","lead":"T2K reports the first double-differential cross-section measurement of pionless muon-neutrino charged-current interactions on oxygen and carbon using kinematic imbalance observables. The joint carbon-oxygen result constrains nuclear-effect models that limit precision in neutrino oscillation experiments such as Hyper-Kamiokande.","discovery_kind":"extension","skeptic_critique":{"model":"grok-4.5","headline":"Residual model dependence in ND280 efficiency/unfolding corrections for the CC0π+Np sample is the load-bearing risk to the claimed double-differential KI distributions and C–O correlations.","rationale":"The reader’s weakest-assumption statement already isolates the single most load-bearing concern visible from the abstract: residual model dependence of efficiency and unfolding corrections. No stronger internal inconsistency or circularity appears in the abstract alone; the novelty of a first joint C/O KI result is plausible and the generator comparisons are standard practice. Because the full text, systematic tables and data release remain unavailable, soundness cannot be audited further, so the verdict stays UNVERDICTED with low confidence. The proposed concrete test is the direct check that would settle whether the concern lands once the paper is fully accessible.","tokens_in":1980,"tokens_out":478,"duration_ms":12393,"concrete_test":"Once the full paper is available, re-compute the double-differential bins and C–O correlation coefficients using at least two substantially different nuclear models as efficiency priors (e.g., NEUT vs. GENIE with alternate FSI); if any key bin or the correlation coefficient shifts by more than the quoted systematic uncertainty, the model-independence assumption fails and the strongest claim weakens.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim—that this is the first joint C/O double-differential KI measurement in the muon-neutrino CC0π+Np channel and that no generator fully describes the data—requires the extracted cross sections to be sufficiently free of nuclear-model bias that observed discrepancies and C–O correlations can be read as genuine constraints. In T2K ND280 analyses of this topology, selection efficiencies and any unfolding of kinematic-imbalance variables (δpT, δφT, etc.) are computed with the same generators under test. The abstract supplies no quantification of residual dependence; if proton-tagging or pion-veto efficiency varies strongly with FSI/2p2h modeling across the measured phase space, the reported distributions and their target correlations can be pulled toward the prior, undermining both the “none fully describe” statement and the claim of reduced systematics for multi-target oscillation experiments.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.5","summary":"The manuscript reports the first double-differential measurement of the muon-neutrino charged-current cross section as a function of kinematic-imbalance (KI) observables for the CC0π+Np topology on oxygen, extracted simultaneously with carbon using T2K ND280. The joint C/O extraction is presented as providing direct sensitivity to target correlations relevant for multi-target oscillation analyses (T2K, Hyper-Kamiokande). Generator comparisons are said to show that none of the widely used models fully describe the data across the measured phase space, motivating improvements in nuclear-effect modeling.","tokens_in":2134,"tokens_out":818,"duration_ms":10669,"significance":"If the extraction is sufficiently free of residual nuclear-model bias, a first joint C/O double-differential KI measurement in the pionless, proton-tagged channel would be a valuable constraint for neutrino-nucleus generators and a concrete input for reducing multi-target systematics in current and next-generation oscillation experiments. The simultaneous-target design and the focus on KI observables are well-motivated. The abstract’s claim that no generator fully describes the data would, if robust, be a useful falsification signal for the community. These strengths cannot be fully assessed from the abstract alone.","major_comments":[{"comment":"Only the abstract is available for this review, so efficiency corrections, background subtraction, unfolding regularization, flux uncertainties, and the quantitative treatment of C–O correlations cannot be audited. The central claim—that residual model dependence does not bias the reported double-differential KI distributions or the claimed target correlations—is load-bearing and cannot be verified without the full analysis description, covariance treatment, and model-variation studies.","section":null},{"comment":"Abstract claim that ‘none of the models fully describe the data across all regions of measured phase space’: without the full text it is impossible to judge how this is quantified (χ², pull distributions, phase-space binning, or visual comparison only). A load-bearing statement of this form requires explicit, reproducible comparison metrics and a clear statement of which phase-space regions drive the disagreement.","section":null},{"comment":"Abstract claim of ‘direct sensitivity to the correlations between two targets’: the joint C/O extraction is presented as reducing systematics for multi-target oscillation experiments. The residual model dependence of proton-tagging and pion-veto efficiencies (and of any unfolding of δpT, δφT, etc.) on the same FSI/2p2h generators under test is the principal risk to reading those correlations as genuine constraints. The abstract supplies no quantification of that residual dependence; the full manuscript must demonstrate that the reported C–O correlations are not pulled toward the prior.","section":null}],"minor_comments":[{"comment":"Abstract: the phrase ‘kinematic imbalance (KI) observables’ is used without naming the specific variables (e.g. δpT, δφT, δpTT). Naming them would improve clarity for non-specialist readers of the abstract.","section":null},{"comment":"Abstract: ‘at least one proton in the final state’ should be stated with the proton momentum/threshold definition used in the selection, even at abstract level, since that threshold strongly affects FSI sensitivity.","section":null}],"recommendation":"uncertain","confidential_remarks":"This is an abstract-only review; full text was not provided. I cannot responsibly recommend accept/minor/major/reject without the analysis sections on efficiency, unfolding, and model-dependence studies. The collaboration and channel are mature and the claim is plausible, but the skeptic’s residual-model-dependence concern is the correct load-bearing risk and must be addressed in any full review. Scope fit for hep-ex is appropriate if the full paper delivers the claimed joint C/O double-differential results with adequate systematics documentation."},"author_rebuttal":null,"desk_editor":{"model":"grok-4.5","letter":"The one thing to know is that this is the first simultaneous carbon–oxygen double-differential measurement of kinematic-imbalance observables in the muon-neutrino CC0π+Np channel. That specific multi-target, multi-dimensional result is new and sits squarely in the middle of what oscillation experiments actually need for nuclear-effect systematics.\n\nWhat the paper does well is the joint extraction itself. Getting the C–O correlations out of the same analysis is the right experimental move for T2K and Hyper-K, and the abstract’s statement that none of the generators fully describe the data across the measured phase space is a clear, useful flag for the modeling community. T2K ND280 methods are mature, so the claim is plausible on its face.\n\nThe soft spot is the standard one for these measurements: efficiency corrections and any unfolding of the KI variables (δpT, δφT, etc.) are computed with the same nuclear generators under test. Residual model dependence from FSI or 2p2h modeling can pull the distributions and the reported target correlations. The abstract gives no quantification of that residual, so the strength of the “none fully describe” claim and the utility of the correlations cannot be checked yet. That is a structural feature of neutrino cross-section work, not a paper-specific red flag visible here; it is simply un-auditable from the abstract. Circularity burden is otherwise low—this is data versus external generators.\n\nThis is for people who build or tune neutrino-nucleus generators and for anyone reducing multi-target systematics in few-GeV oscillation analyses. It is not a paradigm shift, but it is a solid new data product in an established program. It deserves a serious referee; send it to peer review. I would read the full paper and the systematic tables when they appear, but I would not bring the abstract alone to reading group.","headline":"First joint C–O double-differential KI cross section in CC0π+Np from T2K ND280; useful for nuclear systematics, residual model dependence is the usual structural caveat and cannot be audited from the abstract alone.","tokens_in":5093,"tokens_out":492,"would_cite":false,"duration_ms":11741,"reading_group":"no","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.5","headline":"First double-differential muon-neutrino charged-current cross section on oxygen versus kinematic imbalance, extracted jointly with carbon and with no pions and at least one proton in the final state.","keywords":["neutrino–nucleus interactions","charged-current cross section","kinematic imbalance","oxygen target","carbon target","T2K ND280","pionless final state","nuclear effects"],"falsifier":"A future measurement of the same pionless, proton-tagged double-differential distributions on oxygen (or carbon) with an independent detector and different efficiency model that yields statistically incompatible shapes in any of the kinematic-imbalance variables would falsify the present extraction.","tokens_in":2856,"feed_emoji":"⚛️","tokens_out":814,"duration_ms":9299,"temperature":0.7,"pith_summary":"This paper reports the first measurement of the muon-neutrino charged-current cross section on oxygen as a function of kinematic-imbalance observables, for events that produce no pions and at least one proton. The T2K ND280 near detector extracts the cross section simultaneously on carbon and oxygen, double-differentially in several imbalance variables. Those variables are sensitive to nuclear effects that redistribute energy and momentum inside the nucleus, effects that currently limit the precision of neutrino-oscillation experiments. Because the two targets are measured together, the result also supplies the C–O correlations needed when an experiment (T2K, Hyper-Kamiokande) uses multiple nuclear targets. None of the widely used neutrino-event generators fully reproduces the measured distributions across the whole phase space, so the data give concrete guidance on where nuclear models must improve.","feed_headline":"First oxygen cross section vs kinematic imbalance, jointly with carbon","feed_subtitle":"T2K’s double-differential pionless measurement shows no generator fits all phase space and yields C–O correlations for oscillation experimen","key_machinery":"Kinematic-imbalance (KI) observables—quantities constructed from the measured muon and proton momenta that vanish for a free nucleon at rest—serve as the experimental handles that isolate nuclear effects; the double-differential cross sections in these variables, extracted jointly for carbon and oxygen, are the central results that expose model deficiencies and C–O correlations.","core_discovery":"The first double-differential measurement of the pionless, proton-tagged muon-neutrino charged-current cross section on oxygen (and simultaneously on carbon) as a function of kinematic-imbalance observables, obtained with T2K ND280; the joint extraction yields direct experimental sensitivity to carbon–oxygen correlations, and no existing generator describes the data in every region of the measured phase space.","pith_inferences":["If residual model dependence in the ND280 efficiency is later shown to be large, the claimed C–O correlations would have to be re-extracted with a more model-independent technique before they can be used in oscillation fits.","The persistent generator discrepancies in high-imbalance tails suggest that current treatments of short-range correlations or final-state re-scattering are incomplete for light nuclei.","Extending the identical analysis to argon or water-rich targets would test whether the same nuclear deficiencies scale with mass number."],"forward_implications":["Joint C–O cross sections supply the target-correlation matrix needed to reduce a major systematic in multi-target oscillation analyses such as T2K and Hyper-Kamiokande.","Regions of kinematic-imbalance phase space that are poorly described by all generators become priority targets for nuclear-model revision.","The pionless, proton-tagged topology isolates final-state interactions and multi-nucleon effects without pion-absorption ambiguities.","The same KI framework can be reapplied to other nuclei or to antineutrino beams once statistics allow."],"fun_headline_variants":["T2K first joint C-O double-diff pionless νμ CC cross sections vs KI","First oxygen KI cross sections jointly with carbon from T2K ND280","T2K pionless proton-tagged C-O cross sections expose generator shortfalls","Double-differential KI observables measured on oxygen and carbon by T2K","Joint T2K C-O kinematic imbalance data yield nuclear correlation insight"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The efficiency corrections and unfolding used to extract the double-differential cross sections are assumed to be free enough of residual nuclear-model dependence that the reported distributions and C–O correlations remain unbiased.","fun_headline_variants_meta":{"raw":{"variants":["T2K first joint C-O double-diff pionless νμ CC cross sections vs KI","First oxygen KI cross sections jointly with carbon from T2K ND280","T2K pionless proton-tagged C-O cross sections expose generator shortfalls","Double-differential KI observables measured on oxygen and carbon by T2K","Joint T2K C-O kinematic imbalance data yield nuclear correlation insight"]},"model":"grok-4.5","effort":"low","cost_usd":0.004068,"raw_usage":{"total_tokens":1192,"prompt_tokens":723,"num_sources_used":0,"completion_tokens":107,"cost_in_usd_ticks":40680000,"prompt_tokens_details":{"text_tokens":723,"audio_tokens":0,"image_tokens":0,"cached_tokens":128},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":362,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":723,"tokens_out":107,"duration_ms":4245,"temperature":1.0,"reasoning_tokens":362,"cache_read_input_tokens":128,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-07-15T09:12:33.364407+00:00","model_set":{"reader":"grok-4.5"},"falsifier":"A future measurement of the same pionless, proton-tagged double-differential distributions on oxygen (or carbon) with an independent detector and different efficiency model that yields statistically incompatible shapes in any of the kinematic-imbalance variables would falsify the present extraction.","supporting_citations":[],"review_version":2}