{"id":"24c9f4dc-efcd-486e-b6a9-ebc7ec75b2f0","arxiv_id":"2506.13500","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":0,"one_line_summary":"For an RPV supersymmetric sbottom diquark model, SMEFT 4-quark operators describe LHC top-pair data only for squark masses so large that the effects are unobservable, so SMEFT bounds cannot constrain this model.","lead":"Physicists show that a popular shortcut for describing new particles, the SMEFT, cannot describe a supersymmetric diquark model's top-pair signals at the LHC. Whenever the model's effects are large enough to measure, the shortcut gives wrong answers, so LHC bounds on this model must come from the full model, not the shortcut.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The no-overlap conclusion is conditional on a fine-tuned one-light-sbottom spectrum; without an RGE/UV-completion check, the analyzed corner may be unrealizable, limiting the general lesson.","rationale":"Reader's weakest_assumption is the same spectrum assumption, so I partially agree. I would not move the verdict because the paper's central comparison is transparently scoped to this simplified model and the authors flag the unnaturalness; the conditional verdict already captures the need for caveats. The remaining caveats (LO BSM signal, no shipped code, order-of-magnitude direct search) are secondary: they affect quantitative bounds but not the qualitative no-overlap conclusion. The most useful addition would be an RGE/UV-completion check to show the corner is realizable, which would turn a scope limitation into a stronger result.","tokens_in":27036,"tokens_out":13290,"duration_ms":159328,"concrete_test":"Run the two-loop MSSM+RPV RGEs from M_GUT down to the TeV scale with lambda''_313 nonzero and all other RPV couplings zero, scanning non-universal soft masses so that m_btilde_R is in the 0.5-3 TeV range while gluino and other squark masses exceed about 5 TeV; check for tachyonic sbottom mass and Landau poles. If no boundary condition survives, the analyzed parameter region is not UV-realizable, and the general conclusion should be restricted to a low-scale toy model; if viable points exist, the fine-tuning concern is reduced to a question of naturalness rather than realizability.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim is the Sec. 5 statement that there is no region of parameter space of the RPV model that is simultaneously measurable at the LHC and well described by its SMEFT implementation. The demonstration is internally coherent, but its scope rests on the Sec. 2/footnote 7 assumption that btilde_R is the only light superpartner and lambda''_313 the only sizable coupling. The authors themselves call this 'not very natural' and note that RG running tends to destroy the hierarchy; the conclusion is then generalized ('the SMEFT is model independent only in the sense that it does not reproduce the LHC signals of any perturbative model'). Because no RGE or UV-completion analysis is supplied, the analyzed slice may not be realizable in any UV-complete supersymmetric theory, and the practical statement that SMEFT analyses cannot yield present or near-future bounds on this RPV model is not established for realistic spectra. If additional superpartners are light, direct production and cascade decays change the signal and the bounds; if the hierarchy cannot be stabilized, the parameter region is empty. Neither possibility invalidates the pointwise RPV-versus-SMEFT comparison, but both limit the generality of the conclusion.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper asks whether dimension-six four-quark SMEFT operators can faithfully reproduce the LHC top-pair signals of a simplified R-parity-violating supersymmetric model in which only the right-handed sbottom is light and couples through λ''_313. The authors perform tree-level matching to obtain the two Warsaw-basis operators (Eq. 2.7), simulate the full RPV model including on-shell single-sbottom and sbottom-pair production, and compare differential distributions (p_T of top quarks, m_tt, p_T(tt), charge asymmetry) against CMS and ATLAS parton-level data using the experimental covariance matrices. They derive 95% CL limits both in the full RPV model and in its SMEFT implementation, and they find that the SMEFT describes the RPV model only for sbottom masses above roughly 5 TeV, where the effects are far below LHC sensitivity. For all masses and couplings with observable effects, the SMEFT misses the on-shell t-tbar-j resonance contributions and overestimates the off-shell exchange in the high-p_T tails. The paper concludes that there is no parameter region of this RPV model that is simultaneously measurable at the LHC and well described by the SMEFT, and it uses the strong sensitivity of the fits to the quadratic d=6 terms to question the convergence of the SMEFT expansion.","tokens_in":27209,"tokens_out":9930,"duration_ms":109172,"significance":"If correct, this is a valuable cautionary case study for the common practice of translating LHC top-quark measurements into SMEFT bounds and then into constraints on specific UV models. The strengths of the paper are the clean tree-level matching, the direct use of public parton-level distributions with full covariance information, the inclusion of on-shell mediator production in the 'full' model, and the unusually transparent discussion of the model's approximations and unnaturalness. The no-overlap conclusion is supported by several independent observables and by explicit comparisons in tables and figures, so it is likely to be robust within the stated benchmark. The main limitation is that the demonstration concerns one deliberately SMEFT-friendly, fine-tuned slice of parameter space; the broader statement that the SMEFT 'does not reproduce the LHC signals of any perturbative model' is an extrapolation beyond the evidence presented.","major_comments":[],"minor_comments":[{"comment":"The concluding sentence that the SMEFT 'is model independent only in the sense that it does not reproduce the LHC signals of any perturbative model' is stronger than the analysis supports: the paper studies a single scenario, and the authors themselves note that the assumed one-light-sbottom spectrum is unnatural and tends to be destroyed by RG running. The stress-test concern about this point lands as a scope limitation rather than as an error: the pointwise RPV-versus-SMEFT comparison is valid for the defined benchmark, but the phrase 'any perturbative model' should be tempered to something like 'the class of single-mediator, SMEFT-friendly scenarios considered here,' or a short RGE/UV-completion discussion should be added to justify the stability of the hierarchy.","section":"Sec. 5 and Footnote 7"},{"comment":"The statement that the large difference between the O(Λ^-2) and O(Λ^-4) fits 'shows that the expansion in inverse powers of Λ does not converge' is not strictly established by that comparison alone, because a linear-plus-quadratic d=6 fit is not a complete O(Λ^-4) calculation: d=8 interference terms, which are also O(Λ^-4), are omitted and could in principle cancel part of the quadratic term. The direct RPV-versus-SMEFT comparisons do support the failure of the EFT in the sensitive region, so the conclusion is likely correct, but the convergence claim should be rephrased as, for example, 'the large difference is inconsistent with a rapidly convergent expansion at the energy scales probed.'","section":"Sec. 4.7 and Conclusions"},{"comment":"The exclusion curves in Figs. 4, 6, 7, 9, 13, and 15 extend to λ''=4 even though the text states that the constant-width Breit-Wigner approximation is questionable for λ''>3 and that the LO calculation cannot be trusted for λ''>4. The central conclusion is unaffected because the unitarity bound λ''<1.12 covers the main argument, but the displayed curves above λ''≈3 should be shaded or marked as indicative only.","section":"Sec. 4.2 and Sec. 4.7"},{"comment":"There is a duplicated article in 'yields the the upper bounds' in the second paragraph of Sec. 4.4; this should be corrected.","section":"Sec. 4.4"},{"comment":"The 'total' column in Tables 1 and 2 can be negative because the positive t-tbar-j contribution and the negative exclusive-t-tbar interference cancel; the captions should explicitly note that negative values mean the overall BSM contribution changes sign in that bin and should not be read as a physically meaningful positive ratio.","section":"Tables 1 and 2"},{"comment":"The quantitative exclusion limits are derived from leading-order matrix elements for the BSM signal while the SM background is treated at NNLO. The paper cites K-factors near unity for the EFT operators, but a sentence quantifying the expected NLO uncertainty on the full RPV contributions, especially the on-shell t-tbar-j channel, would strengthen the reliability of the numerical bounds and of the no-overlap claim.","section":"Sec. 4.1 and Sec. 5"}],"recommendation":"minor_revision","confidential_remarks":"The paper is honest and well within the journal's scope; the main risk is that the broad concluding sentence about 'any perturbative model' will be quoted out of context. I suggest the handling editor encourage the authors to qualify that statement, and perhaps to add a brief remark on whether the assumed hierarchy can be stabilized by a UV completion, since this is the only point on which the advertised general lesson is weaker than the actual demonstration."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Quick take: this is a genuinely useful counterexample paper. It takes a concrete, SMEFT-friendly RPV sbottom model, matches it at tree level to two 4-quark operators, and shows that the SMEFT description of inclusive top-pair data fails everywhere the model is actually detectable. The on-shell single-sbottom t-tbar-jet channel is the killer: it dominates the strongest constraints and is simply absent from the EFT. The paper earns its main claim.\n\nWhat is new: most SMEFT-vs-UV comparisons stay at the level of “the EFT cannot reproduce a resonance.” Here they quantify the failure for a model with no 2-to-1 resonance, using current CMS and ATLAS parton-level distributions with covariance matrices, and show the EFT overestimates bounds by large factors even in the exclusive t-tbar channel, because dropping the momentum dependence of the propagator is bad at high pT or high mtt. The matching is clean, the simulations are straightforward, and the authors flag their own approximations (constant width, LO BSM signal, single-light-sbottom assumption). No circularity: the Wilson coefficients are derived from the UV model, not fitted to define it.\n\nSoft spots, in order of importance. First, the analyzed parameter slice is fine-tuned. Only btilde_R is light and only lambda''_313 is nonzero; the authors admit this is not natural and that RG running tends to destroy it. That means the no-overlap theorem is really a no-overlap result for this corner. It is a valid counterexample to the claim that a generic SMEFT fit can stand in for a perturbative UV model, but it does not establish that “SMEFT reproduces no perturbative model’s LHC signals.” The concluding generalization is stronger than the evidence. Second, the chi-square limits do not include theory uncertainties on the LO BSM signal, so the quoted 95% CL curves have unquantified error; minor for the qualitative conclusion, more relevant if the bounds are used numerically. Third, no code or model files are shipped, so independent verification means reimplementing MadGraph setups. The direct-search section is admittedly an order-of-magnitude comparison, fine for justifying M_sbottom >= 500 GeV.\n\nWho this is for: anyone using SMEFT global fits to constrain diquark-like or RPV-like UV completions, and anyone arguing about EFT validity at the LHC. It deserves a serious referee; the right outcome is publication after the scope of the conclusion is tightened and the LO signal uncertainty is at least bracketed. I would cite it as a cautionary example.","headline":"A concrete, well-executed counterexample showing SMEFT 4-quark operators fail for an LHC-detectable RPV sbottom model; the main caveat is the fine-tuned spectrum, not the EFT-vs-UV comparison itself.","tokens_in":27778,"tokens_out":2069,"would_cite":true,"duration_ms":20967,"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 paper claims that four-quark SMEFT operators cannot describe the LHC-visible signals of an R-parity-violating sbottom diquark model.","keywords":["SMEFT","R-parity violation","4-quark operators","top pair production","sbottom diquark","effective field theory validity","LHC constraints","unitarity bound"],"falsifier":"Measurable check: at 13 TeV, measure the parton-level $p_T(t_{\\rm high})$ distribution in $t\\bar t+$ jet events with enough statistics to resolve the Jacobian peak at $p_T\\simeq M_{\\tilde b}/2$ for $M_{\\tilde b}\\simeq 1.5$ TeV and $\\lambda''_{313}=1$; the full RPV model predicts this peak while the SMEFT cannot produce it. Conversely, if a SMEFT fit using only the two matched operators, with $C_1^{td}=-C_8^{td}/3>0$, reproduces the full RPV exclusion curves for $M_{\\tilde b}<3$ TeV within the experimental uncertainties of the LHC differential distributions used here, the paper's central claim would be disproved.","tokens_in":26792,"feed_emoji":"⚛️","tokens_out":11394,"duration_ms":105751,"temperature":0.7,"pith_summary":"This paper asks whether four-quark operators of the Standard Model Effective Field Theory (SMEFT) can stand in for a concrete weakly coupled new-physics model when deriving bounds from LHC top-pair data. The model is a supersymmetric one with baryon-number violation, in which a right-handed sbottom acts like a diquark coupling a down quark to a top quark. Matching the sbottom out at tree level gives two dimension-six four-quark operators, but the paper finds that their predictions deviate from the full model precisely where the LHC is sensitive: on-shell sbottom production contributes through $t\\bar t+$ jet channels the EFT omits, and the point-like approximation overestimates the $t$-channel exchange in the high-energy tails. Agreement between the EFT and the full model is reached only for sbottom masses around 5 TeV or above, where the effects are below collider sensitivity for couplings allowed by perturbative unitarity. The paper concludes that present or near-future LHC bounds on this RPV model cannot be obtained from SMEFT analyses.","feed_headline":"Four-quark SMEFT cannot bound an RPV sbottom at the LHC","feed_subtitle":"Effective operators match the full model only where its effects drop below collider sensitivity.","key_machinery":"The load-bearing object is the tree-level matching of the sbottom to two four-quark operators, $O^{(1)}_{td}$ and $O^{(8)}_{td}$, with $C_1^{td}=|\\lambda''_{313}|^2/(3M_{\\tilde b}^2)$ and $C_8^{td}=-|\\lambda''_{313}|^2/M_{\\tilde b}^2$; this is equivalent to replacing the sbottom propagator $1/(q^2-M_{\\tilde b}^2)$ by $-1/M_{\\tilde b}^2$. The argument then runs through a detailed comparison of the full RPV model, with Breit-Wigner propagators for possibly on-shell sbottoms in $t\\bar t j$ and $t\\bar t jj$ channels, and the SMEFT implementation, keeping only the leading order in the two operators, for the distributions measured by the LHC experiments. The failure of the EFT is driven by two mechanisms: the neglect of momentum flow through the $t$-channel propagator, which overestimates the BSM contribution in the tails, and the omission of on-shell sbottom production, which produces a resonance in the top+jet invariant mass and a Jacobian peak at $p_T\\sim M_{\\tilde b}/2$.","core_discovery":"Integrating out the right-handed sbottom generates exactly two dimension-six operators at tree level, the color singlet $O^{(1)}_{td}$ and color octet $O^{(8)}_{td}$, with related Wilson coefficients $C_1^{td}=-C_8^{td}/3>0$. The paper tests whether this SMEFT implementation reproduces the full RPV model by comparing parton-level predictions for inclusive $t\\bar t$ production against the LHC differential measurements of top transverse momenta, the top-pair invariant mass, the top-pair transverse momentum, and the top-pair charge asymmetry. It finds that for sbottom masses up to 3 TeV the SMEFT overestimates the exclusive $t\\bar t$ contribution, sometimes by an order of magnitude or with the wrong sign in high-$p_T$ and high-$m_{t\\bar t}$ bins, while the $t\\bar t j$ channel with an on-shell sbottom, which dominates the strongest constraints, cannot be described by the dimension-six operators at all. Only when $M_{\\tilde b}\\gtrsim 5$ TeV do the two descriptions agree to within roughly 20%, but then the effects are below LHC sensitivity for any coupling satisfying the unitarity bound. The stated conclusion is that no region of parameter space simultaneously gives measurable LHC effects and a reliable SMEFT description.","pith_inferences":["The same failure pattern, tail overestimation plus missing on-shell production, should apply to any weakly coupled $t$-channel mediator coupling a light quark to a top quark, because the EFT breaks down whenever the momentum transfer approaches the mediator mass, $|q^2|\\sim M^2$.","A practical consequence the authors leave implicit is that recasting LHC top-pair data into bounds on such models should use dedicated searches for $t\\bar t+$ jet resonances and Jacobian peaks in top-$p_T$, rather than global SMEFT fits, and the high-luminosity LHC will be better positioned for that search.","One could extend the comparison quantitatively to future LHC runs: as luminosity grows, the measurable region extends toward heavier sbottom masses, and the paper's numbers suggest that SMEFT and full-model predictions will still differ well above 3 TeV, so a forecast of where direct searches overtake SMEFT limits would be a concrete next step.","A model with more than one light superpartner would introduce additional on-shell production channels that the EFT misses entirely, so the numerical failure found here is likely a lower bound on the SMEFT discrepancy for less fine-tuned spectra."],"forward_implications":["SMEFT-based bounds on this RPV model from top-pair data are not reliable for sbottom masses up to at least 3 TeV.","The observables that give the strongest constraints, $p_T(t_{\\rm high})$, $p_T(t_h)$ and $p_T(t\\bar t)$, are dominated by single on-shell sbottom production, which the dimension-six operators do not describe, so the EFT limits cannot be read off as model limits.","Even restricting to the exclusive $t\\bar t$ channel, the SMEFT overestimates the new-physics contribution by factors of two or more in the high-$p_T$ and high-$m_{t\\bar t}$ bins for $M_{\\tilde b}<3$ TeV, so the problem is not only missing channels.","If the high-scale unitarity bound $\\lambda''_{313}<1.12$ is imposed, current data exclude the model only for $M_{\\tilde b}<1.9$ TeV, precisely where the SMEFT implementation fails; for heavier sbottoms the model is beyond LHC reach.","The large difference between linear and quadratic SMEFT fits to the same distributions indicates that the expansion in inverse powers of the new-physics scale does not converge for this model at LHC energies."],"supporting_citations":[{"why":"Supplies the RPV superpotential, the coupling convention for $\\lambda''_{313}$, and the perturbative unitarity bound used to restrict the coupling.","marker":"[40]"},{"why":"Defines the dimension-six operator basis and the notation used for the two operators produced by the matching.","marker":"[9]"},{"why":"Provides the 13 TeV parton-level differential top-pair distributions and covariance matrices used for most exclusion limits.","marker":"[58]"},{"why":"Provides the top-pair charge asymmetry measurement used for the remaining constraints.","marker":"[59]"},{"why":"Supplies the global SMEFT fit results for the Wilson coefficients that the paper uses as the literature comparison baseline.","marker":"[31]"},{"why":"Gives the NLO QCD corrections to the two four-quark operators, justifying the near-unity K-factors used in the SMEFT simulation.","marker":"[60]"},{"why":"Provides the LHC search for pair-produced heavy particles decaying to a top quark and a gluon, used to argue that direct searches do not strongly constrain the sbottom scenario.","marker":"[55]"}],"fun_headline_variants":["SMEFT misses RPV diquark effects at LHC","Four-quark SMEFT cannot reproduce RPV sbottom","SMEFT bounds fail for RPV diquark model","Diquark signals beyond SMEFT reach at LHC","RPV sbottom escapes SMEFT constraints"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The scenario assumes the right-handed sbottom is much lighter than all other superpartners and that the RPV coupling $\\lambda''_{313}$ is the only sizable new coupling, so every other supersymmetric contribution decouples; the authors admit this is not very natural and that renormalization-group running tends to destroy the hierarchy.","fun_headline_variants_meta":{"raw":{"variants":["SMEFT misses RPV diquark effects at LHC","Four-quark SMEFT cannot reproduce RPV sbottom","SMEFT bounds fail for RPV diquark model","Diquark signals beyond SMEFT reach at LHC","RPV sbottom escapes SMEFT constraints"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000235,"raw_usage":{"total_tokens":1563,"prompt_tokens":1071,"completion_tokens":492,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":687,"completion_tokens_details":{"reasoning_tokens":413}},"tokens_in":687,"tokens_out":492,"duration_ms":5521,"temperature":1.0,"reasoning_tokens":413,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T20:00:33.020736+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Measurable check: at 13 TeV, measure the parton-level $p_T(t_{\\rm high})$ distribution in $t\\bar t+$ jet events with enough statistics to resolve the Jacobian peak at $p_T\\simeq M_{\\tilde b}/2$ for $M_{\\tilde b}\\simeq 1.5$ TeV and $\\lambda''_{313}=1$; the full RPV model predicts this peak while the SMEFT cannot produce it. Conversely, if a SMEFT fit using only the two matched operators, with $C_1^{td}=-C_8^{td}/3>0$, reproduces the full RPV exclusion curves for $M_{\\tilde b}<3$ TeV within the experimental uncertainties of the LHC differential distributions used here, the paper's central claim would be disproved.","supporting_citations":[],"review_version":2}