{"id":"c46e0814-927d-4a51-9c1e-16157e68f443","arxiv_id":"2412.19060","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"A coarse two-bin ratio of Drell-Yan transverse momentum cross sections can determine the intrinsic kT width with sensitivity comparable to fine binned spectra, as shown by pseudo-data and CMS data.","lead":"This paper proposes measuring the ratio of low- and high-transverse-momentum Drell-Yan events to extract the intrinsic sideways motion of quarks inside protons, instead of relying on finely binned spectra. The approach gives comparable statistical sensitivity in pseudo-data tests and matches previous CMS-based extractions, while promising smaller systematic uncertainties.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 3% Gaussian momentum-smearing model in Eq. (3.4) is the load-bearing support for the claimed systematics advantage; if the true migration is asymmetric or pT-dependent, the coarse-bin ratio may not actually be safer than fine binning.","rationale":"The reader's weakest_assumption is exactly the 3% Gaussian smearing model in Eq. (3.4) and the low-pT reference assumption. I agree; this is the most load-bearing point because it carries the paper's main advertised advantage (reduced systematics). The pseudodata closure within the same model only shows self-consistency, and the CMS comparison in Figure 7 is a consistency check with Ref. [9] rather than a demonstration that the ratio is robust to realistic detector effects. The paper does include an explicit limitation statement in Section 4, noting that ps requires careful investigation, and it correctly treats the CMS part as a feasibility study, so the concern does not overturn the paper's valid core: a coarse ratio has comparable statistical sensitivity. That is a legitimate, useful finding. But the stronger claim (that it propagates lower systematics) is not yet established. Hence CONDITIONAL remains the right verdict; the paper should be accepted conditional on demonstrating the systematics claim under a more realistic detector-response model, or on clearly demoting that claim to a conjecture.","tokens_in":15026,"tokens_out":2142,"duration_ms":20606,"concrete_test":"Replace Eq. (3.4) with a detector-response check based on the published CMS 2016 muon/electron resolution and efficiency as a function of lepton pT and eta, or better, a smearing matrix from a full detector simulation; rerun the pseudo-data sensitivity test of Section 3 for ps in 1.5-4 GeV. If the pT-ratio fitting uncertainty degrades by more than ~30% relative to the fine-binned fit under the realistic response, the claim that the ratio propagates lower or equal systematics would need to be weakened.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim is that the pT-ratio avoids the large systematics of fine-binned low-pT spectra. The quantitative support is Section 3's pseudo-data test, which models detector momentum response by the single multiplicative Gaussian in Eq. (3.4). That model likely fails to capture real low-pT lepton momentum scale and resolution effects: for low-pT leptons, resolution is degraded, energy loss and reconstruction inefficiencies are asymmetric, and a multiplicative smearing of each dressed lepton does not reproduce the correlated migration of the dilepton pT, m(ll), and rapidity. Since the sensitivity loss from migration in Figures 4-5 is used to argue that the ratio remains as sensitive as fine binning, a more realistic detector response (e.g., CMS/ATLAS full simulation or a migration matrix with off-diagonal correlations) could show larger degradation for the ratio: as ps is the only separator, a smearing tail that pushes events from below to above ps directly dilutes the ratio, whereas fine bins all receive a similar dilution and the shape may retain sensitivity. The CMS extraction in Section 4 uses ps=2 GeV with no per-mass-bin optimization and no validation of Eq. (3.4) against the actual 2016 CMS detector performance, so the feasibility conclusion is only as solid as that model. The paper's own statement that \"the choice of ps value will need careful investigation\" is an explicit limitation, and the fixed ps=2 GeV choice is part of that limitation.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper proposes to determine the intrinsic-kT width q_s in the parton-branching TMD approach from a coarse-grained ratio R = sigma(pT<ll><ps)/sigma(pT>ps) rather than from the fine-binned low-pT Drell-Yan spectrum. After reviewing the PB TMD setup (Sec. 2), the authors generate seven MC templates with different q_s, run a pseudo-data closure test (Sec. 3) comparing fit uncertainties from the fine-binned spectrum and from the ratio, with and without a 3% Gaussian lepton-momentum smearing, and apply the method to CMS 13 TeV data in five m_ll bins with fixed ps=2 GeV (Sec. 4). They find that the ratio has sensitivity comparable to fine binning and yields q_s values consistent with Ref. [9], concluding that the ratio is a viable lower-systematics observable for intrinsic-kT determination.","tokens_in":15353,"tokens_out":5579,"duration_ms":54716,"significance":"The proposal is potentially useful for TMD phenomenology: a robust two-bin ratio would ease experimental challenges in the low-pT region and avoid part of the unfolding and systematics burden. The paper's strengths are the clean statistical closure test with large MC samples, explicit covariance propagation in Eqs. (3.2)-(3.3), use of public TMDlib templates and public CMS data, and honest acknowledgment of the need to optimize ps. However, the central claims are stronger than the evidence: the sensitivity comparison is internal to the PB TMD model, the detector-response model is a single Gaussian smearing, and the comparison with Ref. [9] shares the same theoretical framework. With additional validation, the method could become a valuable complement to fine-binned extractions.","major_comments":[{"comment":"The pseudo-data sensitivity test is a closure fit: the 'pseudo-data' and the fitting templates are generated from the same PB TMD model with the same Gaussian parameterization (Eq. (2.2)), so Figs. 3 and 5 quantify the statistical precision of the fit under the model, not the ability of the pT-ratio to determine qs when the true intrinsic-kT distribution has a different functional form or when the evolution model is misspecified. To support the general statement that 'the intrinsic kT can be determined by measuring its overall strength through the pT-ratio', please add a model-mismatch test (e.g., pseudo-data generated with a non-Gaussian intrinsic-kT or from an independent TMD framework) and report the resulting bias in qs.","section":"Section 3, Figs. 3 and 5"},{"comment":"The claimed systematics advantage rests on the simplified detector model of Eq. (3.4), a multiplicative 3% Gaussian smearing applied to each dressed lepton. Real LHC momentum resolution is pT- and rapidity-dependent, has asymmetric tails from bremsstrahlung and energy loss, and induces correlated migrations in pT(ll), m(ll), and eta(ll); a single constant smearing does not capture these effects. Figures 4-5 therefore do not establish that the ratio is robust to the 'migration effects' that the paper itself identifies as a dominant systematic. Please validate the migration model against a full detector simulation or against the actual migration matrices used in CMS/ATLAS analyses, or at minimum test a range of pT-dependent smearing and migration scenarios and show that the ratio's sensitivity advantage persists.","section":"Section 3, Eq. (3.4)"},{"comment":"The consistency check against Ref. [9] is partially circular: both analyses use the same PB TMD framework, the same MCatNLO+CASCADE setup, the same CMS data, and overlapping uncertainty treatments, so agreement in Fig. 7 demonstrates internal consistency rather than independent validation. Also, the extraction fixes ps=2 GeV for all five mll bins, and the paper itself notes that the choice of ps 'will need careful investigation' (Sec. 4); without a per-mass-bin optimization or a scan over ps, the claim that the ratio reproduces the reference extraction in every mDY region is not fully supported. A comparison with an independent TMD extraction (e.g., analytic resummation fits in Ref. [8]) or an explicit ps scan would make the validation convincing.","section":"Section 4, Fig. 7"}],"minor_comments":[{"comment":"The generator name appears garbled as 'CRAPHGADM'; it should be 'MCatNLO+CASCADE'.","section":"Fig. 1 caption"},{"comment":"Please define pL and pH explicitly as integrals of the pT(ll) distribution over the ranges [0,ps] and [ps,pT,max] (or [ps,infinity)) and state whether these are cross sections or event counts, because Eq. (3.2) assumes uncorrelated statistical uncertainties.","section":"Eqs. (3.1)-(3.2)"},{"comment":"The definition of pT,max is ambiguous when comparing the fine-binned fits and the ratio; specify whether events with pT > pT,max are excluded from both the fine-binned and ratio fits.","section":"Section 3"},{"comment":"In the sentence 'For the last two mDY bins, it is not estimated for the lack of statistics', specify which uncertainty source is meant (the pT-range uncertainty) and describe how the variation was performed in Ref. [9].","section":"Section 4"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is honest about its limitations, and the proposed observable is a reasonable idea. The main risk is overclaiming systematics insensitivity on the basis of an idealized 3% Gaussian smearing. I would urge the editor to require the detector-response validation before publication; if the authors cannot access a full simulation, they should reframe the claims as a statistical sensitivity study with an idealized smearing model and avoid categorical claims about real experimental systematics."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThis paper is worth your time if you care about TMD extractions. The new thing is a two-bin pT ratio – cross section below ps over above ps – used to extract the intrinsic-kT width qs. That is not in the cited literature, and it is a simple idea that could lower the experimental burden in the low-pT region. The pseudo-data sensitivity test is clean: they show the ratio has statistically comparable sensitivity to the fine-binned pT shape, under their templates. The CMS application is a reasonable feasibility check, and the extracted qs values agree with Ref. [9] within uncertainties.\n\nWhat deserves credit: the authors are honest about scope. They state up front this is a feasibility study, not a precision extraction. They explicitly say the choice of ps needs careful investigation. They don't oversell the CMS numbers. That restraint matters.\n\nNow the soft spots, in proportion. The central motivation – lower systematics from unfolding or momentum migration – is not actually demonstrated. The 3% Gaussian smearing in Eq. (3.4) is a toy. Real lepton momentum response is pT-dependent, asymmetric, and correlated with mass and rapidity. If migration pushes events across ps asymmetrically, the ratio could be more degraded than fine bins, not less. The pseudo-data test only includes statistical uncertainties, so it shows statistical precision, not the claimed systematics advantage. Also, the CMS extraction uses a fixed ps=2 GeV for all mass bins, with no optimization or validation against the actual 2016 CMS detector response. The consistency with Ref. [9] is useful but not independent, since it uses the same PB TMD framework.\n\nNone of this kills the idea. The observable is new, plausible, and could be made rigorous with a proper migration-matrix study. But the abstract's claim of \"lower systematic uncertainties\" goes beyond the evidence in the paper. A referee should push on that.\n\nWho is this for: people working on intrinsic-kT determinations, TMD fits, and DY measurements. It deserves a serious referee, with the expectation that the systematics claim will need to be backed by a realistic detector simulation or at least a migration matrix with off-diagonal correlations. I would send it to review.\n\nBest,\n[You]","headline":"A genuinely new two-bin pT-ratio observable for intrinsic-kT extraction, cleanly tested on pseudo-data and CMS data, but the headline systematics advantage rests on a toy detector model and needs a harder look.","tokens_in":15839,"tokens_out":2005,"would_cite":true,"duration_ms":21705,"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":"The intrinsic sideways motion of quarks can be read from a two-bin ratio of Drell-Yan dilepton momenta, with sensitivity matching the full fine-binned spectrum.","keywords":["intrinsic transverse momentum","Drell-Yan production","dilepton transverse momentum","TMD parton distributions","parton branching method","coarse binning","LHC physics","Z boson production"],"falsifier":"Take the same CMS phase space, replace the 3\\% Gaussian lepton-smearing model with a full detector simulation with $p_T$-dependent resolution, and re-run the two-bin fit; if the extracted $q_s$ shifts by more than the quoted uncertainty or becomes incompatible with the fine-binned extraction, the central claim is falsified.","tokens_in":14840,"feed_emoji":"📉","tokens_out":6882,"duration_ms":219560,"temperature":0.7,"pith_summary":"This paper claims that the nonperturbative sideways momentum of quarks and gluons inside the proton—the intrinsic $k_T$—can be pinned down from Drell-Yan lepton-pair data without measuring the finely binned low-$p_T$ spectrum. The proposed observable is a single ratio of the dilepton cross section below a separation momentum $p_s$ to the cross section above it. Pseudo-data tests with parton-branching templates show that this ratio is statistically as sensitive to the intrinsic-$k_T$ width $q_s$ as the full $p_T$ shape, even after 3\\% lepton momentum smearing. Applying the ratio to CMS measurements across dilepton masses from 50 GeV to 1 TeV gives $q_s$ values consistent with an earlier fine-binned extraction. Because coarse bins avoid the worst unfolding and momentum-migration systematics, the claim, if right, makes intrinsic-$k_T$ determination cheaper and more robust at the LHC.","feed_headline":"Two-bin ratio measures intrinsic kT as well as fine bins","feed_subtitle":"Drell-Yan data can skip fine low-pT bins, shrinking unfolding and migration systematics.","key_machinery":"The central object is the $p_T$-ratio of Eq. (3.1), $p_T\\text{-ratio} = p_L/p_H$, with $p_L$ the number of events with dilepton $p_T$ below the separation momentum $p_s$ and $p_H$ the number above it. The machine that produces predictions is the parton branching method for transverse-momentum-dependent evolution, whose starting-scale boundary condition is a Gaussian intrinsic-$k_T$ distribution with width $q_s$; seven template samples with different $q_s$ values provide the shapes to fit. Sensitivity is quantified with a least-squares estimator and a covariance matrix, and detector response is modeled by multiplying each dressed lepton's four-momentum by a factor $(1+g)$ with $g$ sampled from a Gaussian of 3\\% width. The high-$p_T$ bin acts as a fixed-order reference that makes the ratio sensitive to the relative, not absolute, size of the intrinsic contribution.","core_discovery":"The authors' central claim is that the information about intrinsic $k_T$ is essentially an overall shift of strength from low to high dilepton $p_T$, so a two-bin ratio $p_L/p_H$—the cross section with $p_T < p_s$ divided by the cross section with $p_T > p_s$—captures the intrinsic-$k_T$ Gaussian width $q_s$ as well as the fine-binned $p_T$ spectrum does. They support this with template samples generated at seven $q_s$ values: the ratio falls monotonically as $q_s$ increases, and least-squares fits to pseudo-data yield uncertainties comparable to fits of binned shapes with bin widths from 0.5 to 3 GeV. With a 3\\% Gaussian lepton-momentum smearing meant to model detector resolution, the ratio keeps its sensitivity. An extraction from CMS dilepton $p_T$ data in five mass bins, using $p_s = 2$ GeV, returns $q_s$ values consistent with the earlier parton-branching determination in each mass region.","pith_inferences":["We infer that the claimed systematic advantage depends on the detector model: a realistic, $p_T$-dependent resolution with non-Gaussian tails could change the optimal $p_s$ or degrade the ratio's sensitivity, so a full-simulation study is the natural next test.","The same coarse-ratio logic could be applied to other TMD-sensitive observables, such as angular correlations or event-shape variables, wherever the interesting physics appears as a shift between a low- and high-momentum region.","Fixing $p_s = 2$ GeV for all dilepton-mass bins was a practical choice dictated by the published CMS binning; optimizing $p_s$ per mass bin could sharpen the extraction, since the peak of the $p_T$ spectrum moves with $m(ll)$."],"forward_implications":["The intrinsic-$k_T$ width can be extracted from as few as two $p_T$ bins, so future measurements do not need fine binning in the low-$p_T$ region where lepton efficiency and momentum-resolution systematics are largest.","The $p_T$-ratio has statistical sensitivity comparable to the fine-binned $p_T$ shape both at truth level and after 3\\% lepton momentum smearing, so no precision is lost by coarse graining.","Applying the ratio to existing CMS data reproduces the $q_s$ values from a previous fine-binned parton-branching fit, giving cross-checks on both methods.","The separation momentum $p_s$ must be chosen deliberately: too small a $p_s$ dilutes TMD sensitivity, too large a $p_s$ hides the low-$p_T$ information, and the pseudo-data procedure in the paper provides a way to optimize it.","The same methodology can be stress-tested with more complex TMD parameterizations and with very small or very large $q_s$ values to ensure the extraction is unbiased."],"supporting_citations":[{"why":"Provides the previous $q_s$ extraction and the parton-branching template sets used as benchmarks for the $p_T$-ratio results.","marker":"[9]"},{"why":"Supplies the CMS dilepton $p_T$ measurements in five mass bins used for the real-data extraction.","marker":"[16]"},{"why":"Establishes the calculation setup for Z production in the parton branching method, including the matching with NLO matrix elements and showers.","marker":"[13]"},{"why":"Provides the fitted parton densities and the Gaussian intrinsic-$k_T$ boundary condition that define the template samples.","marker":"[20]"},{"why":"Gives the parton branching evolution equations and two-loop kernels that generate the TMD distributions.","marker":"[18]"},{"why":"Introduces the soft-gluon resolution scale used to separate resolvable and non-resolvable branchings in the evolution.","marker":"[17]"}],"fun_headline_variants":["Two-bin ratio captures intrinsic kT with fewer errors","Simple pT ratio beats fine bins for intrinsic kT","Drell-Yan two-bin ratio slashes systematics in kT extraction","Skip fine bins: ratio reveals parton transverse momentum"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that detector momentum response is well approximated by a 3\\% Gaussian smearing of dressed lepton momenta and that the $p_T > p_s$ bin can serve as a $q_s$-independent reference; if real migration is stronger or correlated differently, the claimed sensitivity and systematic advantage could break down.","fun_headline_variants_meta":{"raw":{"variants":["Two-bin ratio captures intrinsic kT with fewer errors","Simple pT ratio beats fine bins for intrinsic kT","Drell-Yan two-bin ratio slashes systematics in kT extraction","Skip fine bins: ratio reveals parton transverse momentum"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000227,"raw_usage":{"total_tokens":1456,"prompt_tokens":911,"completion_tokens":545,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":527,"completion_tokens_details":{"reasoning_tokens":476}},"tokens_in":527,"tokens_out":545,"duration_ms":5990,"temperature":1.0,"reasoning_tokens":476,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T00:57:39.733043+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Take the same CMS phase space, replace the 3\\% Gaussian lepton-smearing model with a full detector simulation with $p_T$-dependent resolution, and re-run the two-bin fit; if the extracted $q_s$ shifts by more than the quoted uncertainty or becomes incompatible with the fine-binned extraction, the central claim is falsified.","supporting_citations":[{"cited_title":"The small kT region in Drell- Yan production at next-to-leading order with the parton branching method","cited_arxiv_id":null,"evidence_quote":"Provides the previous $q_s$ extraction and the parton-branching template sets used as benchmarks for the $p_T$-ratio results."},{"cited_title":"Measurement of the mass dependence of the transverse momen- tum of lepton pairs in Drell-Yan production in proton-proton collisions at √s = 13 TeV","cited_arxiv_id":null,"evidence_quote":"Supplies the CMS dilepton $p_T$ measurements in five mass bins used for the real-data extraction."},{"cited_title":"Production of Z- bosons in the parton branching method","cited_arxiv_id":null,"evidence_quote":"Establishes the calculation setup for Z production in the parton branching method, including the matching with NLO matrix elements and showers."},{"cited_title":"Collinear and TMD Quark and Gluon Densities from Parton Branching So- lution of QCD Evolution Equations","cited_arxiv_id":null,"evidence_quote":"Gives the parton branching evolution equations and two-loop kernels that generate the TMD distributions."},{"cited_title":"Soft-gluon resolution scale in QCD evolution equations","cited_arxiv_id":null,"evidence_quote":"Introduces the soft-gluon resolution scale used to separate resolvable and non-resolvable branchings in the evolution."}],"review_version":1}