{"id":"b3695f14-21a0-499a-adce-2a482ae4088f","arxiv_id":"1908.06996","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":7,"one_line_summary":"In a simplified partial-compositeness model, energy-dependent gluon form factors suppress heavy top partner production by up to an order of magnitude and add a few-percent distortion to quark-initiated top pair production.","lead":"If the top quark is a mixture of an elementary and a composite state, its interactions with gluons should show energy-dependent structure. This paper models that structure with proton-style form factors and shows how top quark and top partner pair production at a hadron collider would change, including a new wiggle in the top pair mass distribution.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Two-gluon amplitude ansatz is the load-bearing weak point: the predicted top-partner suppression and small gg->ttbar corrections are imposed by an arbitrary overall form factor, not derived, and no robustness check is given.","rationale":"The reader's weakest assumption identifies the same point, and I agree. The one-gluon construction is internally consistent: the current in Eq. (10), the rotation to mass eigenstates in Eqs. (13)-(15), and the qqbar cross sections in Eqs. (33)-(36) follow from the Lagrangian in Appendix B, and the low-energy limit matches known EFT operators. The qq->ttbar 'wiggle', while model-dependent in shape, at least follows from the stated dipole ansatz and is a legitimate falsifiable signature. The problem is the two-gluon extension. Equation (43) has the correct limits but is an interpolation, not a derivation. The numerical output is exponentially sensitive to Lambda_T and to the functional form, and no uncertainty or robustness scan is presented. Since the paper's strongest practical statement is about LHC top-partner searches, the missing check is load-bearing. This does not require rejection: the paper is an exploratory phenomenological study and should be read as such. It should remain conditional, with the two-gluon ansatz either derived, scanned over plausible form factors, or explicitly labelled as a toy estimate with no direct benchmark implications.","tokens_in":17985,"tokens_out":7113,"duration_ms":81289,"concrete_test":"Recompute the gg->TT and gg->ttbar cross sections and the ratios shown in Figs. 5 and 6 using the same bare amplitudes but with two alternative gauge-invariant overall form factors: (i) the exponential F of Eq. (38) with Lambda_T = Lambda_c (about 2.2 TeV for the benchmark) instead of 11f; and (ii) a dipole F = (1 - s/Lambda_T^2 e^{i eta})^{-2} symmetrized as in Eq. (38), with Lambda_T = 11f. If the gg->TT suppression relative to point-like changes by more than an order of magnitude, or if the gg->ttbar ratio changes sign or exceeds a few percent, then the stated robustness of the ansatz is refuted and the LHC benchmark recommendation should be treated as parameter-dependent.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The suppression of gg->TT shown in Fig. 5, which underlies the conclusion that point-like top-partner benchmarks overestimate LHC signals, is not a derived consequence of partial compositeness. It is imposed by the ad hoc overall form factor F(t,u,s) of Eqs. (37)-(41), taken from the proton-photon model of Ref. [34], together with the choice Lambda_T = 11f. For the benchmark mT ~ 5.7 TeV, threshold sqrt(s) ~ 2mT gives s ~ 130 TeV^2 while 2 Lambda_T^2 ~ 87 TeV^2, so F is an exponential suppression of order exp(-s/(2 Lambda_T^2)) and dominates the cross section. In the proton case, F alone is not the full amplitude: Ref. [34] requires resonance and handbag contributions, which are simply dropped in Section IV A. The authors flag the arbitrariness ('Despite its arbitrariness...') but give no test showing the conclusions are unchanged. A different scale (e.g. Lambda_T ~ Lambda_c ~ 2.2 TeV from the one-gluon fit) or a different functional form (monopole, dipole, or a form factor attached only to the t/u exchange diagrams) would change the suppression by orders of magnitude. Since both the LHC benchmark criticism and the smallness of the gg->ttbar corrections come from this two-gluon ansatz, it is the least secure condition for the central claim.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript constructs a simplified phenomenological model of top-quark partial compositeness in which the composite top partner T' has gluonic interactions described by Dirac and Pauli form factors (dipole approximation), and the light top quark inherits energy-dependent form factors through mixing. The paper derives explicit cross-section formulas for qqbar -> TT and qqbar -> ttbar (Eqs. (33)-(36)) and extends the prescription to gg -> TT and gg -> ttbar by multiplying the bare amplitudes with an overall form factor F(t,u,s) taken from the proton-photon model of Ref. [34]. Using a benchmark with f = 0.6 TeV, M = 9f, M_D = 5f, kappa_g = 2, lambda = 3 and Lambda_T = 11f, the paper claims that (i) the qqbar -> ttbar invariant mass distribution develops a 'wiggle' beyond the EFT and resonance descriptions, and (ii) composite top partner production is strongly suppressed relative to point-like benchmarks, so that current LHC top-partner searches may overestimate the expected signal. It also argues that gg -> ttbar corrections remain small.","tokens_in":18430,"tokens_out":5892,"duration_ms":63511,"significance":"If the two-gluon form-factor ansatz were either derived or shown to be robust, the paper would be a valuable contribution: it provides explicit amplitudes and cross sections, makes falsifiable predictions (the wiggle in m_ttbar, the suppression of composite top partner production), and connects to existing EFT constraints from Refs. [26,27]. The qqbar -> ttbar analysis in particular is a useful proof-of-principle for going beyond leading EFT operators. However, the significance of the paper's central phenomenological conclusions is currently limited because the two-gluon predictions are imposed by an ad hoc overall form factor, not derived from the composite dynamics, and no robustness checks are provided.","major_comments":[{"comment":"The suppression of gg -> TT with respect to the point-like case in Fig. 5 is not a derived consequence of partial compositeness; it is imposed by the overall form factor F(t,u,s) borrowed from the proton-photon model of Ref. [34] together with the choice Lambda_T = 11f. For the benchmark mT ~ 5.7 TeV, the threshold value sqrt(s) ~ 2mT gives s ~ 130 TeV^2, which is already of order 2 Lambda_T^2 ~ 87 TeV^2, so the exponential factors in Eqs. (38)-(39) dominate the cross section. The assertion in §IV B that 'the particular form of this parametrization does not change our conclusions' is not supported by any variation of Lambda_T or of the functional form, nor by a derivation of F from the composite sector. Because Fig. 5 is the basis for the conclusion that point-like LHC top-partner benchmarks overestimate the expected signal, this is a load-bearing gap that needs to be addressed with a concrete sensitivity study.","section":"§IV A, Eqs. (37)-(39), Fig. 5"},{"comment":"The neglect of the resonance and handbag contributions, which are essential ingredients of the proton-photon model in Ref. [34], is asserted rather than argued. In the composite-Higgs context the spectrum contains hypermesons, including a state with m_rho ~ 6f cited from the lattice, so a resonance near or above threshold could plausibly alter the time-like amplitude. The paper gives no quantitative estimate of the energy scale at which the handbag mechanism becomes relevant for the top sector. Since Eq. (43) and the smallness of the gg -> ttbar corrections in Fig. 6 rely on the same neglect, the robustness of the 'small corrections' claim is not established. A concrete test would be to include a simple resonance pole or a handbag-like term and verify that the ratio in Fig. 6 and the conclusions of Section V are unchanged.","section":"§IV A and §IV B, Eqs. (41) and (43), Fig. 6"},{"comment":"The concluding statement that 'the production of a composite top partner is expected to be suppressed compared to a point-like state' is too strong given the analysis presented. The suppression in the gg-initiated channel is a consequence of the specific form factor F(t,u,s) and the chosen Lambda_T = 11f; without a robustness analysis the paper can only claim this within the adopted benchmark model. The same caveat applies to the statement that the gg -> ttbar corrections remain small, since those corrections are also governed by the same ansatz.","section":"§V, Conclusion"}],"minor_comments":[{"comment":"The horizontal axes are labeled 's [TeV]' in several figures, but the arrow positions (e.g., 2mT ~ 11.4 TeV in Fig. 2 and threshold values in Fig. 5) indicate that the axis actually shows sqrt(s) in TeV, not s in TeV^2. Please relabel the axes consistently.","section":"Figures 2, 5, 6"},{"comment":"There are several typos, including 'namlely' in §III A, 'analougously' in §IV B, 'subsequentially' in Appendix C, and 'offshellness' in Appendix C. These should be corrected.","section":"Throughout"},{"comment":"Reference [32] for the ATLAS charge asymmetry measurement is incomplete; it should include the arXiv number or journal reference so that readers can locate the result.","section":"Reference [32]"},{"comment":"The dipole parametrization in Eq. (23) contains an explicit pole at q^2 = 4M^2; the paper notes it is unphysical and expected to be removed by other contributions, but it would be helpful to state explicitly that the numerical results in the physical region are not affected by this pole for the chosen benchmark.","section":"§III A, Eq. (23)"},{"comment":"The statement that the total qqbar -> ttbar cross section is enhanced by ~1% at the LHC and ~4% with an m(ttbar) > 1 TeV cut is based on CTEQ5 PDFs; using a modern PDF set would be more appropriate, although this does not affect the qualitative conclusions.","section":"§III D"}],"recommendation":"major_revision","confidential_remarks":"The central issue is whether the authors can supply the missing robustness analysis within the scope of a revision. If they can show that the suppression of gg -> TT and the smallness of the gg -> ttbar corrections survive variation of Lambda_T and the form-factor shape, the paper's phenomenological message would be credible. As it stands, the manuscript's own admission of 'arbitrariness' in §IV B is a serious limitation that needs to be addressed head-on rather than with an unsubstantiated assertion."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Colleague,\n\nThe one-gluon part of this paper is solid and worth your time. The authors construct a simplified partial compositeness model with a single vector-like top partner, derive the top quark form factors induced by mixing, and give explicit cross section formulas for qq->ttbar and qq->TT. The key observation—that the full energy-dependent form factor produces a wiggle in the ttbar invariant mass distribution that the leading EFT does not capture—is genuine, and the argument that qq->ttbar is more sensitive than gg->ttbar is convincing. They are also honest about what is phenomenological.\n\nThe soft spot is the two-gluon amplitude. For gg->TT and gg->ttbar, the tree-level amplitude is multiplied by an overall form factor borrowed from a proton-photon model, with the scale Lambda_T = 11f. For their benchmark mT ~ 5.7 TeV, the threshold sits at sqrt(s) ~ 11.4 TeV, where the exponential factor is already suppressive. So the headline claim—that composite top partner production is suppressed relative to point-like benchmarks—is imposed by the ansatz, not derived from partial compositeness. They flag the arbitrariness but do not test alternative functional forms or scales. A monopole or a different scale could change the suppression by orders of magnitude. The smallness of gg->ttbar corrections is similarly dependent on that choice. I would not call this a fatal flaw; it is an exploratory study. But the LHC-facing conclusion should be softened until a robustness check is done.\n\nMinor issues: there are no uncertainties on the numerical predictions, and the PDF set (CTEQ5) is old. The wiggle itself also depends on the dipole approximation and the absorptive phase; it is a reasonable benchmark, not a robust prediction, and the authors acknowledge resonance contributions may modify it.\n\nWho is this for? Composite Higgs and top partner phenomenologists who need benchmarks beyond EFT. If I were an experimental search team, I would treat the one-gluon results as a useful proof of principle and the gg->TT suppression as a cautionary tale, not a quantitative input.\n\nMy recommendation: send it to peer review. The formalism is clear, the paper is honest, and the qq->ttbar part stands on its own. Ask for a robustness section on the two-gluon form factor and a more careful statement of the conclusions. That is a manageable revision.","headline":"A transparent form-factor benchmark for top compositeness: the qq->ttbar wiggle is the real payoff, but the gg->TT suppression claim rests on an untested ansatz.","tokens_in":18879,"tokens_out":2991,"would_cite":false,"duration_ms":28897,"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":"If the top quark is partially composite, energy-dependent form factors would produce a wiggle in top-pair production and suppress heavy top-partner signals, beyond what any effective-field-theory truncation predicts.","keywords":["top quark","partial compositeness","form factors","composite Higgs","top partner searches","LHC phenomenology","chromomagnetic dipole moment","dipole approximation"],"falsifier":"A high-luminosity measurement of the $m_{t\\bar t}$ spectrum in quark-initiated production would settle the benchmark: the paper predicts an energy-growing excess, about 4% for $m_{t\\bar t}>1$ TeV, with a wiggle near $\\sqrt{s}\\sim M_D$. Finding neither, while top-partner searches observe rates matching the point-like prediction, would falsify the model. The form-factor ansatz itself could also be checked by a first-principles calculation of the top-partner's gluon form factor in a concrete composite model; if that calculation is not dipole-like, the phenomenological conclusions would need to be revisited.","tokens_in":17755,"feed_emoji":"⚛️","tokens_out":15727,"duration_ms":148147,"temperature":0.7,"pith_summary":"This paper argues that partial compositeness of the top quark can show up at colliders through energy-dependent form factors, not just through the leading effective-field-theory operators. In a simplified model in which the composite top partner's gluon interactions are written with chromo-Dirac and chromo-Pauli form factors borrowed from proton electromagnetism, the light top quark inherits modified couplings through the partial-compositeness mixing. The paper finds that in $q\\bar q\\to t\\bar t$ the full form factors produce a wiggle in the top-pair invariant-mass distribution that no EFT truncation or resonance description predicts, and that composite top-partner pair production is suppressed relative to the point-like state used as the standard LHC benchmark. If correct, this gives colliders a new observable for top compositeness and implies that current top-partner search strategies may be assuming too large a signal.","feed_headline":"Top compositeness predicts a wiggle in top-pair masses","feed_subtitle":"If true, current LHC searches for heavy top partners overestimate the signals they should see.","key_machinery":"The central object is a pair of chromo form factors, $F_1(q^2)=1+(q^2/M^2)f_1(q^2)$ and $F_2(q^2)$, for the fully composite top partner, modeled on the proton's Dirac and Pauli form factors and parametrized with the dipole form $(1-q^2/M_D^2)^{-2}$ together with a magnetic-moment normalization $\\kappa_g$ and an absorptive phase $\\eta$. Partial-compositeness mixing with angles $s_L$ and $s_R$ induces the corresponding top-quark form factors $F_1^{tg}$ and $F_2^{tg}$, which carry the energy dependence that the leading EFT expansion misses. For gluon-initiated processes, the paper additionally multiplies the bare amplitude by an overall form factor $F(t,u,s)$ with scale $\\Lambda_T$, taken from the proton-exchange model of $\\gamma\\gamma\\to p\\bar p$, to preserve gauge invariance and crossing symmetry. The energy dependence of these form factors, not their Taylor coefficients, is what produces the wiggle and the suppression.","core_discovery":"On its own terms, the paper claims that when the compositeness scale $\\Lambda_c$ lies below the mass of the new resonances $M_\\rho$, the top-gluon interaction cannot be summarized by a small set of EFT coefficients: the vertex is an energy-dependent form factor, and its full shape matters in the intermediate window $\\Lambda_c< E < M_\\rho$. Modeling the heavy composite top partner as a nucleon-like object with chromo-Dirac and chromo-Pauli form factors in the dipole approximation, and rotating to mass eigenstates with mixing angles $s_L$ and $s_R$, the authors derive the modified top-quark current and compute quark- and gluon-initiated pair production. The central results are a wiggle in the $q\\bar q\\to t\\bar t$ invariant-mass distribution that is absent in both EFT and resonance parametrizations, and a sizable suppression of top-partner pair production relative to a point-like top partner, which the authors state should be taken into account in future LHC searches.","pith_inferences":["One extension the paper leaves implicit is to compute $F_1(q^2)$ and $F_2(q^2)$ in a specific composite model, such as the lattice theory used for the benchmark masses; a measured wiggle position could then be converted into a direct determination of the compositeness scale.","The overall form factor used for $gg$-initiated amplitudes is an ansatz taken from proton-photon scattering, and the paper explicitly neglects resonance and handbag contributions; whether the predicted suppression survives in a given UV model should be treated as open.","The same form-factor logic could be applied to the top's electroweak interactions with $Z$ and $W$ bosons, where single-top and associated production would provide complementary energy-dependent probes of the same compositeness.","Because the $f_1$ operator is related by the equations of motion to four-fermion interactions that do not feed $gg\\to t\\bar t$ at tree level, the quark-initiated differential shape is arguably the most direct experimental window onto the Dirac form factor."],"forward_implications":["A differential measurement of the $m_{t\\bar t}$ distribution in quark-initiated top-pair production could search for a wiggle near the form-factor scale; in the benchmark, the total cross section rises by about 1%, and by about 4% when $m_{t\\bar t}>1$ TeV.","LHC searches for heavy top partners that compare data with a point-like production benchmark will overestimate the expected signal if the top partner is composite; the suppression is energy-growing for a purely composite state and saturates to a constant for a partially composite one.","The $gg\\to t\\bar t$ channel is a less sensitive probe of top compositeness than $q\\bar q\\to t\\bar t$, because the Dirac form factor does not contribute at tree level and the Pauli term is doubly suppressed by mixing angles and by the need to flip helicity.","Existing EFT bounds on anomalous top-gluon couplings may be conservative, because the full form factors can exceed the leading EFT terms in the intermediate energy window and may not be captured by a few Wilson coefficients.","The form-factor interactions also generate single-top-partner channels $pp\\to t\\bar T$ and $pp\\to T\\bar t$ at higher momenta, which the paper identifies as a new QCD production mechanism worth investigating."],"supporting_citations":[{"why":"Introduces the partial-compositeness mechanism for fermion masses, which is the conceptual basis for the top-quark mixing.","marker":"[1]"},{"why":"Supplies a concrete composite-Higgs UV completion with top-partner candidates and defines the class of models the paper considers.","marker":"[2]"},{"why":"Provides the semiphenomenological dipole fits to nucleon form factors that the paper adapts to the composite top partner.","marker":"[14]"},{"why":"Provides the two-component model for nucleon form factors in the time-like region that motivates the absorptive phase used in the top-gluon form factors.","marker":"[15]"},{"why":"Re-analysis of the time-like nucleon form factors in the same two-component model, used together with [15] to fix the proton-inspired parameters.","marker":"[16]"},{"why":"Lattice computation of the composite-Higgs baryon spectrum used to set the benchmark masses, $M=9f$ and $m_\\rho=6f$.","marker":"[20]"},{"why":"Supplies the existing bound on the top chromomagnetic dipole moment against which the mixing-suppressed Pauli form factor is compared.","marker":"[26]"},{"why":"Provides the constraint on the nonstandard top-gluon interaction used to normalize the Dirac form-factor Wilson coefficient.","marker":"[27]"},{"why":"Parton distribution set used to convert the partonic cross sections into the quoted LHC predictions.","marker":"[31]"},{"why":"The proton-exchange model for $\\gamma\\gamma\\to p\\bar p$ that provides the overall form factor $F(t,u,s)$ used for gluon-initiated top and top-partner production.","marker":"[34]"}],"fun_headline_variants":["Top compositeness wiggle beyond EFT","Top pairs reveal form-factor wiggle","Form factors shift top-partner search predictions","Energy-dependent top interactions reshape LHC signals","LHC top-partner searches need form-factor reality check"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise is that the dipole form factor used for the proton, applied to the composite top partner and as an overall factor in the two-gluon amplitudes, accurately describes the energy dependence of the new strong dynamics; if the true form factors have a different shape, the wiggle and the suppression will move.","fun_headline_variants_meta":{"raw":{"variants":["Top compositeness wiggle beyond EFT","Top pairs reveal form-factor wiggle","Form factors shift top-partner search predictions","Energy-dependent top interactions reshape LHC signals","LHC top-partner searches need form-factor reality check"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000406,"raw_usage":{"total_tokens":2076,"prompt_tokens":876,"completion_tokens":1200,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":492,"completion_tokens_details":{"reasoning_tokens":1146}},"tokens_in":492,"tokens_out":1200,"duration_ms":10214,"temperature":1.0,"reasoning_tokens":1146,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-14T12:28:52.934303+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"A high-luminosity measurement of the $m_{t\\bar t}$ spectrum in quark-initiated production would settle the benchmark: the paper predicts an energy-growing excess, about 4% for $m_{t\\bar t}>1$ TeV, with a wiggle near $\\sqrt{s}\\sim M_D$. Finding neither, while top-partner searches observe rates matching the point-like prediction, would falsify the model. The form-factor ansatz itself could also be checked by a first-principles calculation of the top-partner's gluon form factor in a concrete composite model; if that calculation is not dipole-like, the phenomenological conclusions would need to be revisited.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Introduces the partial-compositeness mechanism for fermion masses, which is the conceptual basis for the top-quark mixing."},{"cited_title":"(4) Let t and T be the mass eigenstates such that (t′ R T′ R ) = (−cR sR sR cR )(tR TR ) and (t′ L T′ L ) = ( cL sL −sL cL )(tL TL ) (5) 4 where cR,L = cosθR,L and sR,L = sinθR,L","cited_arxiv_id":null,"evidence_quote":"Supplies a concrete composite-Higgs UV completion with top-partner candidates and defines the class of models the paper considers."},{"cited_title":"Iachello, A","cited_arxiv_id":null,"evidence_quote":"Provides the semiphenomenological dipole fits to nucleon form factors that the paper adapts to the composite top partner."},{"cited_title":"Sigma-assisted natural composite Higgs","cited_arxiv_id":"1809.09146","evidence_quote":"Lattice computation of the composite-Higgs baryon spectrum used to set the benchmark masses, $M=9f$ and $m_\\rho=6f$."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the existing bound on the top chromomagnetic dipole moment against which the mixing-suppressed Pauli form factor is compared."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"The proton-exchange model for $\\gamma\\gamma\\to p\\bar p$ that provides the overall form factor $F(t,u,s)$ used for gluon-initiated top and top-partner production."}],"review_version":1}