{"id":"f355b5fd-fff8-43d0-b1b4-395d91970172","arxiv_id":"2508.14988","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":3,"one_line_summary":"The first search for a Higgs boson produced with a charm quark and decaying to a W-boson pair sees no excess, and combined with the diphoton channel limits the Higgs-charm coupling to below 47 times the standard model value at 95% confidence.","lead":"Searches for a Higgs boson produced together with a charm quark, where the Higgs decays through two W bosons into an electron, a muon, and neutrinos. No signal is found in the 2016-2018 CMS data, and new upper limits are set on this process and on the Higgs-charm coupling.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Irreducible H+c-bkg modeling is the load-bearing concern: fixed shape/normalization from simulation with a borrowed 50% uncertainty, no control region, and -87% anti-correlation with cH in the 2POI fit.","rationale":"The reader's weakest_assumption identifies exactly this: the modeling of the irreducible H+c-bkg background. My stress-test agrees and elaborates why it is load-bearing. The final state is identical to the signal, the DH-bkg separator is only moderately powerful (AUC 73-78%), and the 2POI fit exhibits -87% anti-correlation, showing that the two processes are nearly degenerate. The normalization uncertainty is borrowed from a different process (ggH+bb), and no dedicated shape uncertainty or control region validates the H+c-bkg template. If this background is mis-modeled, the measured mu_cH and the observed limit 1065 would shift, and the combined kappa_c constraint could change. However, this is a standard, honestly reported limitation in a null-result search; the analysis includes systematic uncertainties and the result is statistically consistent within 1.5 sigma. Therefore the reader's CONDITIONAL verdict is appropriate, but I do not see a reason to move to ACCEPT or REJECT. The central claim is plausible and internally consistent; the verification gap is partly the lack of public data artifacts and partly the irreducible-background sensitivity already noted.","tokens_in":40290,"tokens_out":8289,"duration_ms":97887,"concrete_test":"Re-run the 1POI fit after replacing the H+c-bkg template with an alternative generated in the 3FS scheme (massive charm) or with factorization/renormalization scales varied by factors of 0.5 and 2, keeping all other settings unchanged. If the observed upper limit on mu_cH shifts by more than ~50% (comparable to the assigned normalization uncertainty) or the best-fit mu_cH moves by more than one standard deviation, the H+c-bkg modeling is under-covered and the headline result is not robust.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central limit claim (observed/expected limit 1065/506, combined |kappa_c| < 47) depends on separating the cH signal from the irreducible H+c-bkg background (Fig. 2), which has identical final-state particles and similar kinematics. In the 1POI fit, H+c-bkg is fixed to simulation with a 50% normalization uncertainty borrowed from the ggH+bb calculation [43]; in the 2POI fit it is floated and is -87% anti-correlated with the signal, degrading the limit from 1065 to 1804. This second-best-fit behavior shows that the data cannot cleanly distinguish cH from H+c-bkg. The dedicated DH-bkg classifier has only 73-78% AUC, so the separation power is modest. The shape of H+c-bkg is taken directly from simulation, with no dedicated control region or data-driven validation, and no explicit shape uncertainty is assigned to H+c-bkg as a whole (the FS shape uncertainty is applied to cH and bH, not to the H+c-bkg contribution). If the H+c-bkg normalization or shape is mis-modeled, the extracted mu_cH and the headline limit shift; the 50% uncertainty may be underestimated, as ggH+bb is not the same process as the top-loop H+c production of Fig. 2. The observed limit being about 2x above expected (a 1.5 sigma pull) further underscores that small background mismodeling could move this result noticeably.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper reports a search for Higgs boson production in association with a charm quark (cH) in the H->WW->e nu mu nu final state using 138 fb^-1 of CMS Run 2 data. Events are selected with an e-mu pair, missing transverse momentum, and at least one charm-tagged jet, split into Nc-j=1 and Nc-j>1 signal regions plus high-m_ll and top control regions. Two BDT classifiers (Dbkg and DH-bkg) are combined with k-means binning, and a binned likelihood fit extracts the cH signal strength mu_cH. In the 1POI scenario, where the irreducible H+c-bkg background is constrained to the SM prediction with a 50% uncertainty, the observed (expected) 95% CL upper limit is mu_cH < 1065 (506). In the 2POI scenario, where H+c-bkg is floated, the limit is 1804 (1097) and is -87% anti-correlated with cH. Combined with the preceding diphoton cH search, the result is |kappa_c| < 47 (51) at 95% CL under the flat-direction assumption.","tokens_in":40539,"tokens_out":11314,"duration_ms":129697,"significance":"The analysis is competently executed and follows standard CMS practice: data-driven tt normalization, two control regions, a detailed systematic inventory (Table 3), and an explicit 2POI cross-check. The limit-setting is not circular: the signal predictions are defined by externally fixed SM cross sections, and the kappa_c interpretation uses a stated published assumption. The main contribution is the first cH search in the H->WW channel; its expected sensitivity improves the combined kappa_c constraint from the diphoton-only expected 72.5 to 51, although the observed combined limit (47) is not better than the diphoton-only observed limit (38.1). The key weakness is the modeling of the irreducible H+c-bkg background, which is load-bearing for the 1POI result.","major_comments":[{"comment":"The 1POI limit depends on separating cH from the irreducible H+c-bkg background (Fig. 2). The DH-bkg AUC is only 73-78%, and the H+c-bkg template is taken from simulation with no dedicated validation; the 50% normalization uncertainty is borrowed from ggH+bb [43] and no shape uncertainty is assigned to this component. The 2POI fit demonstrates the degeneracy: H+c-bkg is -87% anti-correlated with cH, and the observed limit degrades from 1065 to 1804. Please add a robustness test using an alternative H+c-bkg template, a shape uncertainty, or a control region enriched in H+c-bkg, or promote the 2POI result to the primary result.","section":"Sections 5-7"},{"comment":"The bH contribution, which is about eight times larger than cH (sigma = 660 vs 90 fb) and enters through the 27% b-jet mistag rate, is reported to be -89% correlated with cH. bH carries the same borrowed 50% normalization uncertainty and no dedicated control region. A conservative check with a larger bH uncertainty or an alternative bH template should be shown to establish that the cH limit is not driven by bH modeling assumptions.","section":"Sections 3 and 7"}],"minor_comments":[{"comment":"The HEPData DOI is given as 10.17182/hepdata.123456, which appears to be a placeholder. Please update to the actual record.","section":"Reference [23]"},{"comment":"The first row is garbled ('Nc-j =1 =1'). It should read '=1' for the Nc-j=1 SR column and '>1' for the Nc-j>1 SR column.","section":"Table 1"},{"comment":"The sentence 'the invariant mass (the pT) of the dilepton pair must be greater than 12 (30) GeV' should be separated into two explicit requirements, e.g., m_ll > 12 GeV and pT_ll > 30 GeV.","section":"Section 4"},{"comment":"Please state explicitly that the observed combined limit |kappa_c| < 47 is not an improvement over the diphoton-only observed limit |kappa_c| < 38.1 [21]; the gain from adding the H->WW channel appears only in the expected limit (72.5 to 51).","section":"Section 7 / Abstract"}],"recommendation":"major_revision","confidential_remarks":"This is a solid CMS search that is likely publishable after the H+c-bkg modeling is addressed with additional validation or by reframing the primary result. The placeholder HEPData DOI should also be corrected. I do not see a circularity problem in the limit-setting procedure."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"What you should know: this is the first search for Higgs production in association with a charm quark in the H->WW->e nu mu nu channel, using 138 fb^-1. It sets an observed (expected) limit of 1065 (506) times the SM cH rate, and the combination with the earlier diphoton cH search gives |kappa_c| < 47 (51). The result is a clean null; nobody is claiming evidence.\n\nThe paper does several things well. The analysis follows standard CMS practice: two signal regions split by c-jet multiplicity, two control regions, data-driven tt normalization, a dedicated BDT (DH-bkg) to separate cH from the irreducible H+c-bkg process (AUC 73-78%), and a binned likelihood fit with a detailed systematic inventory. The limits are set against external SM predictions, so there is no circularity. The authors also report the 2POI fit with H+c-bkg floated, and they are transparent about the resulting -87% correlation. That is honest reporting.\n\nThe soft spots are real but not fatal. The irreducible H+c-bkg background has no dedicated control region; its normalization is fixed from simulation with a 50% uncertainty borrowed from the ggH+bb calculation [43], which is not the same process as the top-loop H+c production of Fig. 2. No explicit shape uncertainty is assigned to H+c-bkg as a whole. In the 2POI fit, floating this background degrades the limit from 1065 to 1804. The observed limit is about twice the expected value, a 1.5 sigma pull, so small background mismodeling could shift the result noticeably. And the HEPData record is still a placeholder, so independent verification of the fit internals is not yet possible.\n\nNone of this undermines the central claim: this is a sensitive, well-reported null search. The combined |kappa_c| < 47 constraint is about an order of magnitude weaker than the direct H->cc limit, but it is a genuinely different production-side probe, and the WW channel is new.\n\nWho should read it: anyone tracking Higgs-charm coupling constraints and LHC Higgs production probes. It deserves a serious referee; the main requests should be for the HEPData content and a clearer discussion of H+c-bkg shape uncertainties, perhaps a control region in a future iteration. I would accept it for peer review and expect it to be published after those checks.","headline":"First cH search in H->WW->e nu mu nu; competently done null result, but sensitivity is weak and the irreducible H+c-bkg modeling is the main soft spot.","tokens_in":41147,"tokens_out":1474,"would_cite":false,"duration_ms":17979,"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":"A search of 138 fb^-1 of LHC proton-proton collisions finds no evidence for Higgs boson production in association with a charm quark (cH) in the H→WW→eνμν final state, and sets the first cH limit in this decay channel.","keywords":["Higgs boson","charm quark","Yukawa coupling","kappa_c","associated production","H to WW","CMS","LHC"],"falsifier":"Run the identical selection on the full Run 3 dataset (about 450 fb^-1 total): under this paper's background model the expected limit should improve from 506 by roughly sqrt(138/450), and no excess beyond 3 sigma should appear in the high-DH-bkg bins of the Nc-j=1 signal region. An excess there, or a sharply different observed limit, would indicate the H+c-bkg template is wrong.","tokens_in":40059,"feed_emoji":"🔬","tokens_out":6291,"duration_ms":73167,"temperature":0.7,"pith_summary":"Using the full 13 TeV Run 2 dataset (138 fb^-1), this search looks for a Higgs boson produced alongside a charm quark and decaying to an electron-muon neutrino pair. No such signal is observed: the measured cH yield is compatible with the background-only expectation within 1.5 standard deviations, and the 95% CL upper limit on the cH signal strength is 1065 (expected 506) times the standard model prediction in the main fit. Combined with the previous CMS cH search in the diphoton channel, the analysis constrains the Higgs-charm Yukawa coupling modifier to |κc| < 47 (expected 51) at 95% CL. This is the first cH search in the WW→eνμν final state and provides a production-based probe of the charm Yukawa coupling that is complementary to direct H→cc decay searches.","feed_headline":"CMS caps Higgs-charm coupling at 47 times the standard model","feed_subtitle":"No cH signal in WW decays in 138/fb; combined production bound now at 47 times SM.","key_machinery":"The analysis is carried by two boosted-decision-tree classifiers plus charm-jet tagging. Dbkg separates cH from the ~90% top-quark background; DH-bkg separates cH from the irreducible H+c-bkg background, which has the same final state but no direct charm-Yukawa vertex. The distinction between fixing versus floating the H+c-bkg normalization (the 1POI versus 2POI fits) sets the main limit, and the flat-direction assumption converts the cross-section limit into a bound on |κc|.","core_discovery":"The central result is a 95% confidence-level upper limit on the cH production signal strength of 1065 (506 expected) times the standard model value when the normalization of the irreducible H+c-bkg background is fixed (1POI fit). When that background is floated (2POI fit), the limit loosens to 1804 (1097) because the two parameters are 87% anti-correlated. Combining the fixed-background fit with the previous CMS diphoton cH search yields |κc| < 47 (51 expected) at 95% CL, the tightest production-based constraint on the charm Yukawa coupling. The analysis separates the cH signal from the dominant top-quark background using one boosted decision tree (Dbkg) and from the kinematically similar H+","pith_inferences":["A data-driven handle on H+c-bkg could come from bH events, which share the same heavy-flavor associated-production physics; calibrating DH-bkg on a bH-enriched region might reduce the 50% modeling uncertainty and sharpen the 2POI fit.","The strong cH–bH correlation (observed at -89%) suggests that a joint cH+bH fit with a common heavy-flavor nuisance parameter could improve the cH limit.","At the HL-LHC, the expected 506 limit at 95% CL should improve roughly as the square root of luminosity; reaching standard-model sensitivity will require both more data and a factor-of-~20 reduction in the flavor-scheme and H+c-bkg uncertainties."],"forward_implications":["The cH process in the WW→eνμν channel is not observed in 138 fb^-1; the expected standard-model rate is more than 500 times below the current sensitivity.","Combined with the diphoton search, the production-based bound |κc| < 47 is the strongest from cH production, though it remains far above the direct H→cc decay bound of |κc| < 5.5.","In the 2POI fit, H+c-bkg and cH are 87% anti-correlated, so letting the H+c-bkg normalization float degrades the limit by about 70%; separating the two processes is the constraining factor.","The analysis is limited by statistical uncertainties today, but theoretical uncertainties from flavor-scheme choice and heavy-flavor modeling will dominate at the high-luminosity LHC."],"supporting_citations":[{"why":"Supplies the previous cH search in the diphoton channel that is combined here to obtain the |κc| < 47 bound.","marker":"[21]"},{"why":"Provides the ggH+bb theoretical uncertainty that sets the 50% normalization uncertainty on heavy-flavor H-bkg modeling.","marker":"[43]"},{"why":"Names the DeepJet algorithm used for charm jet tagging via the CvsL and CvsB discriminants.","marker":"[16]"},{"why":"Establishes cH production as a probe of the Higgs-charm Yukawa coupling.","marker":"[20]"},{"why":"Justifies the flat-direction assumption used to translate the mu_cH limit into a |κc| constraint.","marker":"[92]"},{"why":"Identifies the generator (MadGraph5_aMC@NLO) used to produce cH and bH simulated samples in the 4FS and 5FS schemes.","marker":"[32]"}],"fun_headline_variants":["CMS caps Higgs-charm coupling at 47 times SM","CMS tightens Higgs-charm coupling limit to 47 times SM","Higgs-charm coupling held below 47 times SM by CMS","CMS: Higgs-charm coupling under 47 times SM","Combined CMS search limits charm coupling to 47 times SM"],"cache_read_input_tokens":2688,"weakest_assumption_plain":"The result rests on the assumption that the irreducible H+c-bkg background—a Higgs boson produced with a charm jet but without a direct charm-Yukawa vertex—is modeled well enough that the DH-bkg classifier separates it from the cH signal, with its normalization known to within the assigned 50% uncertainty when it is not floated.","fun_headline_variants_meta":{"raw":{"variants":["CMS caps Higgs-charm coupling at 47 times SM","CMS tightens Higgs-charm coupling limit to 47 times SM","Higgs-charm coupling held below 47 times SM by CMS","CMS: Higgs-charm coupling under 47 times SM","Combined CMS search limits charm coupling to 47 times SM"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.001103,"raw_usage":{"total_tokens":4461,"prompt_tokens":793,"completion_tokens":3668,"prompt_tokens_details":{"cached_tokens":256},"prompt_cache_hit_tokens":256,"prompt_cache_miss_tokens":537,"completion_tokens_details":{"reasoning_tokens":3582}},"tokens_in":537,"tokens_out":3668,"duration_ms":28499,"temperature":1.0,"reasoning_tokens":3582,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-05T18:11:34.314175+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Run the identical selection on the full Run 3 dataset (about 450 fb^-1 total): under this paper's background model the expected limit should improve from 506 by roughly sqrt(138/450), and no excess beyond 3 sigma should appear in the high-DH-bkg bins of the Nc-j=1 signal region. An excess there, or a sharply different observed limit, would indicate the H+c-bkg template is wrong.","supporting_citations":[{"cited_title":"Search for the associated production of a Higgs boson with a charm quark in the diphoton decay channel in pp collisions at √s = 13 TeV","cited_arxiv_id":null,"evidence_quote":"Supplies the previous cH search in the diphoton channel that is combined here to obtain the |κc| < 47 bound."},{"cited_title":"Taming a leading theoretical uncertainty in HH measurements via accurate simulations for bbH production","cited_arxiv_id":"2307.09992","evidence_quote":"Provides the ggH+bb theoretical uncertainty that sets the 50% normalization uncertainty on heavy-flavor H-bkg modeling."},{"cited_title":"Jet Flavour Classification Using DeepJet","cited_arxiv_id":"2008.10519","evidence_quote":"Names the DeepJet algorithm used for charm jet tagging via the CvsL and CvsB discriminants."},{"cited_title":"Probing the Charm Yukawa Coupling in Higgs + Charm Production","cited_arxiv_id":"1507.02916","evidence_quote":"Establishes cH production as a probe of the Higgs-charm Yukawa coupling."},{"cited_title":"More light on Higgs flavor at the LHC: Higgs couplings to light quarks through $h + \\gamma$ production","cited_arxiv_id":"2008.12538","evidence_quote":"Justifies the flat-direction assumption used to translate the mu_cH limit into a |κc| constraint."}],"review_version":1}