{"id":"29507f28-1b7f-4427-b1d8-f259da0ea523","arxiv_id":"2512.21290","paper_version":3,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":5,"one_line_summary":"FCC-ee could measure the total ZH production cross section to 0.31% (0.52%) precision at 240 (365) GeV by combining leptonic and hadronic Z recoil analyses.","lead":"This simulation study shows that a future electron-positron collider, FCC-ee, could measure the total rate of Higgs-boson-plus-Z production to 0.31% precision at 240 GeV. The result combines electron, muon, and hadronic Z decays and is claimed to be independent of how the Higgs decays.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Model-independence claim relies on bias tests limited to SM decay modes; a moderate BSM branching ratio into untested topologies can bias sigma_ZH above the quoted 0.31%.","rationale":"The paper is a well-executed sensitivity study, and the statistical projections are plausible within the stated Monte Carlo framework. However, the strongest framing—'model independence confirmed at the level of the obtained precision'—is not supported by the evidence. The bias tests in Section 7 perturb only SM decay modes, while the analysis is meant to measure the inclusive ZH cross section without assumptions about Higgs decays. The hadronic selection efficiency varies by several percent across decay modes, and the H->invisible test at 1% injection already produces a combined bias (0.34%) slightly larger than the quoted 0.31% uncertainty. The paper excuses this because the SM invisible BR is small, but that excuse is exactly what a model-independent measurement cannot rely on: BSM decays could have sizable branching ratios into phase-space regions not covered by the tests. The final paragraph of Section 7 acknowledges this possibility but asserts, without calculation, that such effects would be within the quoted uncertainties. That assertion should be tested directly, not assumed. This does not overturn the paper's status as a useful projection, but it does mean the conclusion should remain conditional until the model-independence claim is tested against explicitly non-SM decay topologies. I therefore recommend no change to the reader's CONDITIONAL verdict.","tokens_in":16293,"tokens_out":4113,"duration_ms":45474,"concrete_test":"Using the existing H->invisible signal sample at sqrt(s)=240 GeV, replace a few percent (e.g., 5%) of the SM Higgs decays with H->invisible while keeping sigma_ZH fixed, regenerate the combined recoil-mass templates, rerun the full fit, and compare the bias to the quoted 0.31%. If the bias exceeds 0.31%, the model-independence claim fails; repeat with a generic low-multiplicity BSM decay sample to confirm.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim that sigma_ZH is model-independent at 0.31% (240 GeV) is only as strong as the bias tests in Section 7. Those tests perturb SM branching ratios by 5% (leptonic) or 1% (hadronic/combination) and declare success if biases are within about one statistical error. This does not cover non-SM Higgs decays. Section 4.3 reports hadronic selection efficiencies spanning +8.5/-3.3% around 72.91%, so an untested decay mode with a few-percent BR and efficiency at the extremes shifts the inclusive yield by more than the quoted precision. The point is not hypothetical: Table 2 shows H->invisible with a 1% injected perturbation gives +0.34% combined bias, already larger than the 0.31% quoted uncertainty; the paper calls it acceptable only because the SM invisible BR is tiny. A BSM invisible BR at the few-percent level (or a low-multiplicity exotic mode) would plausibly scale that bias well above the quoted precision. The final paragraph of Section 7 concedes exotic scenarios are not exhaustively covered but asserts without derivation that such effects would be 'encompassed by the quoted measurement uncertainties.' That assertion is exactly what needs testing. Systematics are also asserted negligible without a detailed budget, but the model-independence gap is the primary issue.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The paper presents Monte Carlo projections for a model-independent measurement of the e+e- -> ZH cross section at FCC-ee using the recoil-mass technique in the Z->mu+mu-, Z->e+e-, and Z->qq channels at sqrt(s)=240 and 365 GeV, with integrated luminosities of 10.8 and 3.12 ab^-1. The analysis uses WHIZARD/PYTHIA/DELPHES fast simulation, a unified object and kinematic selection, BDT discriminators, and binned maximum-likelihood fits to the recoil-mass (and, for the hadronic channel, jet-pair mass) distributions. The quoted combined uncertainties are 0.31% at 240 GeV and 0.52% at 365 GeV. Model independence is argued through selection-efficiency comparisons and through bias tests that inject 5%/1% shifts in Standard Model Higgs branching ratios and compare the resulting fit biases to the quoted uncertainties.","tokens_in":16652,"tokens_out":4312,"duration_ms":43856,"significance":"If fully supported, this would be an important result: it would establish FCC-ee as capable of the most precise model-independent determination of sigma_ZH, with direct implications for the absolute HZZ coupling and for the normalization of the Higgs coupling program. The paper has notable strengths: it provides a consistent treatment of leptonic and hadronic Z-recoil channels at two energies, includes Z->tau+tau- and Z->nu-nu contributions in the signal definition, uses conservative branching-ratio injection tests as a concrete falsifiable check, and clearly reports the decay-mode dependence of selection efficiencies. However, the model-independence claim is currently broader than the tested scenarios, and one reported bias (H->invisible in the combination) is numerically larger than the quoted total uncertainty. The projected precision is plausible, but the manuscript needs additional work to substantiate the central claim.","major_comments":[{"comment":"The bias tests only perturb SM Higgs branching ratios, yet the model-independence claim covers beyond-SM scenarios. The combination's H->invisible bias is +0.34% against a quoted total uncertainty of 0.31%; the paper accepts this only because the SM invisible branching ratio is small. A BSM Higgs with a few-percent invisible branching ratio (or another low-multiplicity exotic mode) could plausibly produce a bias well above 0.31%, since the hadronic selection efficiency and BDT response for such modes sit at the extremes of Figs. 5 and 7. The final paragraph's assertion that such effects 'would be encompassed by the quoted measurement uncertainties' is not derived or tested. Please add explicit injection tests for representative BSM scenarios (e.g., H->invisible with BR = 1%, 2%, 5%; H->light-quark jets; low-multiplicity final states) and either demonstrate biases below 0.31% or enlarge t","section":"Section 7, Table 2, final paragraph"},{"comment":"The hadronic selection efficiency varies by +8.48%/-3.28% around 72.91%, which the paper acknowledges exceeds a decay-mode-independent selection criterion. The 1% BR-injection tests in Table 2 are not equivalent to populating an untested mode at the efficiency extremes. For example, a 1% BR in a mode with 81% efficiency (the +8.5% extreme) changes the inclusive detected yield by about 0.08%, while a 5% BR changes it by about 0.4%, comparable to or larger than the 0.31% quoted precision. Please quantify the mapping between the efficiency spread and the cross-section bias for such scenarios, or explicitly restrict the claimed model independence to the tested SM-like final states.","section":"Section 4.3, Figs. 5 and 10"},{"comment":"The quoted 'total uncertainties' appear to be statistical only, but the fitting strategy assigns 1% normalization uncertainties to backgrounds and states that other systematics are negligible without giving a detailed budget. For a headline precision of 0.31%, the treatment of nuisance parameters matters. Please document how the 1% background normalization uncertainties are propagated (or why they are not), and provide a breakdown of luminosity, energy-scale, background-shape, and BDT-related uncertainties. If Table 1 is statistical only, say so explicitly in the table caption and text; if it is a total, justify the claimed sub-percent systematics.","section":"Sections 5.2 and 6"}],"minor_comments":[{"comment":"The text quotes 0.57% for the hadronic channel at 365 GeV and 1.35% for the combined leptonic channels at 365 GeV, while Table 1 gives 0.56% and 1.32%. Please align the text with the table.","section":"Section 8 vs Table 1"},{"comment":"The sentence claiming that combining both energy points yields about 0.06% statistical precision on sigma_ZH is not derived in this paper. Either cite the source or remove the statement, since the analyses presented give different combined numbers.","section":"Section 1"},{"comment":"The coefficients A and B are described as optimized constants but their units/normalization are not specified. If they are dimensionless weights, state that; if they carry units, define them.","section":"Equation (4.1)"},{"comment":"The text says the bias tests include 'invisible decays within representative beyond-the-Standard-Model scenarios,' but Table 2 contains only SM H->inv. as a single row. Please clarify what BSM scenario was actually simulated, or revise the sentence.","section":"Section 7"}],"recommendation":"major_revision","confidential_remarks":"The paper is a solid and useful projection, but the model-independence claim is currently stronger than the evidence. The main fix is manageable: add BSM injection tests and quantify the impact of the hadronic efficiency spread, and either provide a systematics budget or relabel the quoted uncertainties as statistical. I would not reject the paper; the central method is sound and the result is likely correct once the claims are matched to the tests."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Dear colleague,\n\nThis is a competent FCC-ee sensitivity study that gives the most precise projected sigma_ZH numbers so far: 0.31% at 240 GeV and 0.52% at 365 GeV, from a combined leptonic+hadronic recoil-mass analysis. The unified workflow at two energies is genuinely new; previous ILC/CEPC work treated channels separately or extrapolated. The event selection, BDT setup, and fits are clearly described, and the leptonic channel efficiency is flat across Higgs decay modes, which is nice.\n\nThe soft spot is the model-independence claim. The bias tests only perturb SM branching ratios, and the acceptance criterion is \"within about one sigma of the fit's own statistical uncertainty.\" That is not a test of model independence; it is a test of the fit's ability to absorb SM variations. The hadronic selection efficiency spreads +8.5/-3.3% across decay modes, and the combination bias for H->invisible is +0.34% against a quoted 0.31% uncertainty. The paper waves this off because the SM invisible BR is tiny, but a BSM invisible BR at the few-percent level would push the bias above the quoted precision. The final paragraph of Section 7 admits exotic scenarios are not exhaustively covered and then asserts, without demonstration, that such effects would be \"encompassed by the quoted measurement uncertainties.\" That assertion needs either a wider set of injected topologies or a stated caveat that the model-independence guarantee is limited to SM-like decay modes.\n\nThe systematic treatment is also thinner than the 0.31% precision would ultimately require. The paper says beam-energy spread, luminosity, etc. are negligible, but there is no detailed budget. That is annoying for a projection, though not disqualifying.\n\nOverall: the projected precisions are plausible Monte Carlo statements, and the paper is a step forward for the FCC-ee Higgs program. But the strongest framing—\"model independence confirmed at the level of the obtained precision\"—overreaches the evidence. I would send this to peer review: the analysis is important enough that referees should press the authors to either broaden the bias tests or soften the claim. I would not quote the cross-section number without that caveat.","headline":"A solid FCC-ee sensitivity projection with genuinely new combined-channel numbers, but the model-independence claim is stretched past what the bias tests actually show.","tokens_in":17155,"tokens_out":2964,"would_cite":true,"duration_ms":27494,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"FCC-ee can pin the total ZH production cross section to 0.31% at 240 GeV by reconstructing the recoiling Z boson in its electron, muon, and hadronic decays, with model independence demonstrated through branching-ratio bias tests.","keywords":["ZH production cross section","recoil mass method","FCC-ee","model independence","Higgs couplings","hadronic Z decay","leptonic Z decay","future lepton collider"],"falsifier":"Simulate a non-SM Higgs decay mode that is not covered by the bias tests (e.g., H->4mu via a hidden sector) with the same fast-simulation and analysis chain, replacing, say, 5% of the H->bb events in the signal template. If the fitted sigma_ZH shifts by more than 0.31% at 240 GeV, the model-independence claim would be falsified.","tokens_in":16166,"feed_emoji":"⚛️","tokens_out":4308,"duration_ms":49566,"temperature":0.7,"pith_summary":"This paper argues that FCC-ee can measure the total Higgs-strahlung cross section sigma(e+e- to ZH) to a relative precision of 0.31% at sqrt(s)=240 GeV (10.8 ab^-1) and 0.52% at 365 GeV (3.12 ab^-1) without assuming a specific Higgs decay pattern. The measurement uses the recoil-mass method: identify the associated Z boson decay, then compute the mass of the system recoiling against it, which is insensitive to how the Higgs decays. The analysis is the first to combine consistently the Z->e+e-, Z->mu+mu-, and Z->qq final states for this purpose, using a common leptonic selection, an orthogonal hadronic selection, and a simultaneous statistical fit. The claim of model independence is supported by bias tests that perturb the Standard Model Higgs branching ratios and show the extracted cross section shifts less than the quoted uncertainty. If realized, this would be the most precise model-independent determination of the ZH cross section planned at any lepton collider, calibrating the absolute Higgs coupling g_HZZ.","feed_headline":"FCC-ee could measure ZH cross section to 0.31%","feed_subtitle":"Combining Z->e, mu, and hadronic recoils at 10.8 ab^-1 yields the most precise model-independent Higgs production rate yet.","key_machinery":"The recoil-mass method is the central object: m_recoil^2 = (sqrt(s) - E_ff)^2 - p_ff^2, where the difermion system comes from the associated Z boson decay. Because the selection uses only the kinematics of the reconstructed Z decay products (lepton pair or jet pair), it minimizes sensitivity to the Higgs decay mode. The analysis combines a BDT discriminator for signal-background separation with a binned maximum-likelihood fit: leptonic channels fit the recoil mass in two BDT regions, while the hadronic channel fits the two-dimensional m_recoil-versus-m_jj distribution, also in two BDT regions, to constrain backgrounds more tightly. Orthogonality among channels is enforced by vetoing events w","core_discovery":"The central claim is that a model-independent measurement of the ZH production cross section at FCC-ee reaches total uncertainties of 0.31% at 240 GeV and 0.52% at 365 GeV when all three Z decay modes (electron, muon, hadronic) are combined in a single likelihood fit. The hadronic channel alone provides 0.38% (0.56%) precision at 240 (365) GeV, and the leptonic channels improve it by 23% (8%). The analysis treats the sum of all ZH final states, including Z->tau+tau- and Z->nu nu events that pass selection, as one parameter of interest, extracted from recoil-mass distributions in two multivariate (BDT) regions for leptonic channels and from a two-dimensional fit in the (m_recoil, m_jj) plane","pith_inferences":["The bias tests cover only shifts among Standard Model Higgs decay modes and a representative invisible decay; a genuinely exotic decay with a different topology (e.g., H->4 muons or long-lived particles) could populate phase space in a way not tested, and the paper's own admission that the hadronic selection efficiency varies by +8.5%/-3.3% across modes suggests the 0.31% precision may degrade if ","The 0.31% figure is statistical plus background-normalization (1%) uncertainties, and the paper asserts all other systematics are negligible; in practice, jet energy scale, BDT training bias, or correlations among background templates at the 0.1% level would need to be demonstrated with full simulation or data control regions, which is left implicit.","The same recoil-mass selection, being based only on Z kinematics, could be adapted to measure differentially in the Higgs recoil momentum or the Z production angle, providing sensitivity to anomalous couplings (e.g., EFT operators) without re-optimizing the model-independence criteria.","Since the low-BDT region is used to constrain background normalizations, the analysis implicitly trusts Monte Carlo background shapes; a data-driven sideband subtraction could serve as a cross-check and would be a logical next step in the experimental validation."],"forward_implications":["If the 0.31% precision is achieved, it would provide a model-independent normalization for all other Higgs coupling measurements at FCC-ee, since sigma_ZH is proportional to g_HZZ^2 and the product sigma_ZH x BR(H->X) scales as g_HZZ^2 g_HXX^2 / Gamma_H.","Combined with a direct measurement of the Higgs width from H->ZZ* decays, the measurement enables extraction of absolute Higgs couplings without relying on the Standard Model assumption for the total width.","The analysis demonstrates that the hadronic Z decay channel, despite its larger decay-mode dependence, contributes substantial sensitivity (0.38% alone at 240 GeV) and improves the leptonic-only result, providing a template for future lepton colliders.","The study at 365 GeV adds sensitivity to the Higgs width through the interplay of WW-fusion and ZH production, improving the overall Higgs programme at FCC-ee.","The quoted precision of 0.31% would surpass the current projections for other proposed lepton colliders, establishing FCC-ee as the leading facility for model-independent Higgs coupling determinations."],"fun_headline_variants":["FCC-ee projected to nail ZH cross section to 0.31%","Model-independent ZH measurement: 0.31% precision","ZH cross section at FCC-ee: combined precision 0.31%","Most precise model-independent ZH rate expected"],"cache_read_input_tokens":2304,"weakest_assumption_plain":"The model-independence conclusion rests on the assumption that the Standard-Model Higgs decay composition used to build the signal template, together with the 5% and 1% branching-ratio shifts injected in the bias tests, is close enough to the true Higgs decay composition that any bias from untested or exotic decay modes falls within the quoted 0.31% uncertainty.","fun_headline_variants_meta":{"raw":{"variants":["FCC-ee projected to nail ZH cross section to 0.31%","Model-independent ZH measurement: 0.31% precision","ZH cross section at FCC-ee: combined precision 0.31%","Most precise model-independent ZH rate expected"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000227,"raw_usage":{"total_tokens":1363,"prompt_tokens":851,"completion_tokens":512,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":595,"completion_tokens_details":{"reasoning_tokens":440}},"tokens_in":595,"tokens_out":512,"duration_ms":5451,"temperature":1.0,"reasoning_tokens":440,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-03T14:08:49.134952+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Simulate a non-SM Higgs decay mode that is not covered by the bias tests (e.g., H->4mu via a hidden sector) with the same fast-simulation and analysis chain, replacing, say, 5% of the H->bb events in the signal template. If the fitted sigma_ZH shifts by more than 0.31% at 240 GeV, the model-independence claim would be falsified.","supporting_citations":[],"review_version":1}