{"id":"b7fb9b97-4f2f-4bb6-a88c-646aa28f0ae2","arxiv_id":"1402.7065","paper_version":3,"verdict":"ACCEPT","confidence":"HIGH","novelty_score":6.0,"correctness_risk":"low","formal_verification":"none","parameter_count":0,"one_line_summary":"Of the minimal one- and two-field extensions that can explain the muon g-2 discrepancy, 8-TeV LHC data already exclude several, and nearly all remaining scenarios fall within the reach of 14-TeV running.","lead":"A systematic survey of the simplest new particles that could explain the muon's anomalous magnetic moment, each scenario confronted with LEP and 8-TeV LHC data. Several minimal explanations are already excluded, and the authors argue the 14-TeV run should settle nearly all the rest.","discovery_kind":"unclear","skeptic_critique":{"model":"selfhosted/deepseek-v4.1-flash","headline":"The '8-TeV rules out a subset' claim holds, but the abstract/conclusion's 'almost all'/'all' framing outruns the body: four mixing-fermion scenarios are explicitly beyond 14-TeV reach, and the marginal vector-boson exclusions rest on un-validated recast acceptances.","rationale":"The reader's weakest_assumption is well chosen: every mass bound in Table 2 scales with the assumed branching fractions, and the authors say so explicitly in §6. Because that caveat is acknowledged, I looked for what remains unresolved. Two things do. First, the abstract's 'almost all' and the conclusion's 'all of the minimal models' are stronger than §4 and §6 support: the four mixing-vector-fermion scenarios are stated to be beyond 14-TeV reach, so the honest summary is 'most,' not 'all.' This is a scope overstatement, not a calculation error, and it is easily fixed. Second, the marginal 8-TeV exclusions (V±+ψ0, VA+ψD) rest on recasting SUSY searches onto scalar/vector topologies with parton-level cuts and no validated efficiency maps; the two-body scalar decay kinematics differ from three-body gaugino decays, so the acceptance is uncertain at the O(1) level. The robust exclusions (φD+ψA, φD+ψD, φD+ψT, φA+ψT) survive this because their LHC bounds sit well above the LEP-surviving regions. So the central claim holds; the verdict should stay ACCEPT, with a request to soften the abstract/conclusion and to quantify the recast uncertainty for the vector-boson cases.","tokens_in":30874,"tokens_out":9446,"duration_ms":160860,"concrete_test":"Re-run the SRnoZc (3ℓ+MET) and four-lepton recasts for V±+ψ0 and VA+ψD using full kinematic distributions or a fast detector simulation (e.g. Delphes) rather than the parton-level 'basic selection cuts' of §6.1. If the 95% CL bound on MV (V±+ψ0) falls below ~300 GeV, or on Mψ (VA+ψD) below ~200 GeV, those scenarios un-exclude and the 'subset' narrows to the scalar cases; if the bounds hold, the concern does not land.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim has two halves. The first — 8-TeV data already exclude a subset of viable models — is supported: φD+ψA and φD+ψD are excluded, and φD+ψT's LHC bound (Mφ > 380 GeV, Table 2) sits far above the only LEP-surviving region (Mφ,ψ ~ 100–150 GeV, §5), so it survives even a factor-of-two acceptance error. The second half is where the framing outruns the body. The abstract says 'almost all viable scenarios can be tested conclusively with 14-TeV data' (abstract:s5), and the conclusion says 'all of the minimal models considered in this work can thus be either excluded or conclusively tested.' But §4 states plainly that mixing vector fermions 'cannot be excluded at the 14-TeV LHC,' and §6 lists ψD+ψ±, ψD+ψ0, ψD+ψA, ψD+ψT as viable while declining to do collider phenomenology for them. That is four of eleven viable scenarios — not 'almost all,' and not 'all.' Separately, the marginal 8-TeV exclusions (V±+ψ0 at MV > 373/476 GeV; VA+ψD at Mψ > 296 GeV) sit close to the LEP-surviving regions (MV,ψ ~ 100–300 GeV, §5), so a modest recast-acceptance error could un-exclude them. The authors acknowledge the branching-fraction caveat explicitly ('the reader should bear in mind...'), but they do not quantify it, and they do not flag the scope gap in the abstract.","agreement_with_reader":"agree"},"referee_report":{"model":"selfhosted/deepseek-v4.1-flash","summary":"The manuscript performs a model-independent study of whether new weakly coupled particles at the electroweak scale that can account for the muon g-2 discrepancy can be probed at the LHC. The authors enumerate one- and two-field extensions of the Standard Model with spin and weak isospin up to one, compute the one-loop contributions to a_mu with FeynArts supplemented by two independent reduction codes, apply LEP and electroweak-precision constraints, identify the scenarios that can explain the discrepancy at one and two sigma, and recast published 8-TeV ATLAS and CMS searches to set mass bounds. They then extrapolate these bounds to a 14-TeV, 300 fb^-1 run by rescaling cross sections. The paper reports that 8-TeV data already exclude a subset of the viable simplified models and that the 14-TeV run can probe most of the remainder.","tokens_in":31207,"tokens_out":5923,"duration_ms":115901,"significance":"The paper is a useful and reusable map from the muon g-2 anomaly to concrete collider signatures. Its value lies less in any single number than in the systematic enumeration of minimal field content, the explicit one-loop results collected in Appendix A, and especially the model-independent four-lepton contact-interaction coefficients in Appendix B, which other authors can apply directly to their own models. The cross-checked loop calculation and the explicit statement of assumptions (MFV, degenerate multiplets, vector-like couplings) are strengths. The mass bounds in Table 2 are falsifiable predictions that can be tested as more LHC data accumulate.","major_comments":[{"comment":"The scope claim in the abstract and conclusion is not consistent with the body of the paper. The conclusion states that 'Combining LEP and 14-TeV LHC data, all of the minimal models considered in this work can thus be either excluded or conclusively tested,' and the abstract says 'almost all viable scenarios can be tested conclusively with 14-TeV data.' But Section 4 states explicitly that mixing vector fermions 'cannot be excluded at the 14-TeV LHC,' and Section 6 declines to perform collider phenomenology for the four scenarios psi_D+psi_pm, psi_D+psi_0, psi_D+psi_A, and psi_D+psi_T. That is four of the eleven viable scenarios listed at the start of Section 6, which is 'most' rather than 'almost all,' and certainly not 'all.' The 'all' in the conclusion is directly contradicted by Section 4. The authors should reword both statements to make the mixing-fermion exception explicit, or explain why those scenarios are excluded by some argument not given in Section 4.","section":"Abstract (abstract:s5) and Section 8 (Conclusions)","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The 14-TeV projections rescale 8-TeV acceptances by the ratio of parton-level cross sections, an approximation the authors themselves call 'admittedly rather ad hoc.' For the marginal exclusions this matters: the V_pm+psi_0 bound (M_V > 373 GeV for a singlet, 476 GeV for a doublet) and the V_A+psi_D bound (M_psi > 296 GeV) sit close to the LEP-surviving regions (M_V,psi ~ 100-300 GeV, Section 5), so a modest error in the assumed selection efficiency could un-exclude them. The paper should attach an estimated uncertainty band to these projections, or at minimum soften the 'conclusively tested' language for the marginal vector-boson scenarios, since the claim of conclusive testing rests on an unvalidated acceptance extrapolation.","section":"Section 6.2 and Table 2","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The authors acknowledge that the LHC bounds assume no decay channels beyond those listed in Table 2, and state that additional channels 'would reduce the observable signal at the LHC and thus weaken the limits presented below.' This caveat is stated but not quantified. Because every mass bound in Table 2, and therefore the claim that a subset of models is already excluded, scales with the assumed branching fractions, a short quantitative statement would strengthen the paper: for example, how far does the M_phi_D > 395 GeV bound move if an unlisted decay drains 30% of the rate, and does the phi_D+psi_T exclusion survive? This is a request to make an acknowledged limitation concrete, not a challenge to the result.","section":"Section 6, Table 2","authors_acknowledge":null,"authors_acknowledge_p":null}],"minor_comments":[{"comment":"The bullet on pp -> phi^pm phi^0 states that the ATLAS bound 'eliminates all allowed parameter space of Delta a_mu for phi_D+psi_pm and phi_D+psi_A.' However, phi_D+psi_pm is not among the viable scenarios listed at the start of Section 6, and Section 5 does not identify it as a viable explanation of the discrepancy. This appears to be a typo for phi_D+psi_D; please check and correct.","section":"Section 6.1, first bullet","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"Table 2 lists rows for phi_0+psi_D, but Section 5 analyzes only phi_0+psi_pm. Please clarify whether phi_0+psi_D is a distinct scenario carried over from the text or a typographical duplication.","section":"Table 2","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"References [8] and [21] are identical (Peskin and Takeuchi, Phys. Rev. D 46, 381 (1992)). One of them should be removed and the citations merged.","section":"References [8] and [21]","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The numerical factor 8.6 x (0.03 x 200 GeV / (|epsilon_i|_max M_i)) in Eq. (31) is not derived in the text. A one-line explanation of where the 8.6 and the 200 GeV reference scale come from would help the reader reproduce the estimate.","section":"Eq. (31)","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The caption notes that the 14-TeV projection is 'dotted for V_pm+psi_D' but does not explain why this one scenario is treated differently from the others. A brief clarification would improve readability.","section":"Figure 7 caption","authors_acknowledge":null,"authors_acknowledge_p":null},{"comment":"The notation c_M Delta'_psi, c_psi Delta_psi, and c'_psi Delta'_psi is introduced without spelling out which combinations are retained and which are dropped in the subsequent approximations. A sentence making the bookkeeping explicit would help.","section":"Section 2.2, Eq. (5)","authors_acknowledge":null,"authors_acknowledge_p":null}],"recommendation":"minor_revision","confidential_remarks":"The technical core of this paper is sound: the loop calculation is cross-checked, the LEP contact-interaction bounds are applied conservatively, and the model-independent coefficients in Appendix B are a genuine community resource. The main issue is a scope overstatement in the abstract and conclusion that is contradicted by Section 4; the fix is a rewording plus a short sensitivity statement, not new analysis. I would be glad to see a revised version."},"author_rebuttal":null,"desk_editor":{"model":"selfhosted/deepseek-v4.1-flash","letter":"The thing to know: this is a reference paper, and a good one. Freitas, Lykken, Kell and Westhoff walk through every one- and two-field extension up to spin one and isospin one that can plausibly produce the muon anomaly, compute the one-loop contributions, apply LEP and 8-TeV bounds, and project to 14 TeV. The loop amplitudes are done with FeynArts and cross-checked by two independent reduction codes — the right standard. Table 7, the model-independent one-loop coefficients for four-lepton contact interactions from a pair of new fields, is the piece I'd actually pull off the shelf; as far as I know that hadn't been assembled before, and it's reusable for anyone constraining a two-field lepton coupling at LEP. The negative results are also worth having: the scalar triplet, the neutral vector, the single vector leptons — all dead, and now stated in one place with the reasons attached. The note in §4 that their doublet-plus-singlet result agrees with Kannike et al. except for a sign in one doubly-charged term is the kind of thing I want authors to say out loud. My one real complaint is framing. The abstract says 'almost all viable scenarios can be tested conclusively with 14-TeV data' [abstract:s5], and the conclusion says 'all of the minimal models considered in this work can thus be either excluded or conclusively tested.' But §4 says plainly that mixing vector fermions cannot be excluded at 14 TeV, and §6 declines to do collider phenomenology for those four scenarios for exactly that reason. That's four of eleven viable cases, and the body knows it. The abstract should too — it's a two-sentence fix, not a structural problem. Second, smaller: the marginal 8-TeV exclusions (V±+ψ0, VA+ψD) sit close to the LEP-surviving regions, so a modest recast-acceptance error could un-exclude them. The authors flag the branching-fraction caveat explicitly but don't quantify it; a line on how much the bounds move under a drained decay mode would help. The 14-TeV projections rescaling fixed efficiencies are crude and the authors say so. None of this touches the load-bearing claim, which rests on direct searches, not the optional LEP loop bounds. Who should read it: anyone working on light new physics coupled to muons, and anyone who will need these contact-interaction coefficients. Worth a serious referee.","headline":"A careful, useful enumeration of which minimal g-2 explanations survive LEP and 8-TeV data — the body is honest, but the abstract's 'almost all' oversells the 14-TeV reach.","tokens_in":31866,"tokens_out":1002,"would_cite":true,"duration_ms":17420,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"pith_extraction":{"msc":[],"pacs":["13.40.Em","12.60.-i","14.80.-j","13.85.Rm"],"model":"selfhosted/deepseek-v4.1-flash","headline":"The muon's magnetic moment can be used to predict what the LHC should already have seen, and the paper works out which candidate explanations survive.","keywords":["muon anomalous magnetic moment","g-2 anomaly","LHC searches","simplified models","vector-like leptons","minimal flavor violation","LEP contact interactions","collider recasting"],"falsifier":"The claim would be broken by exhibiting a parameter point inside the perturbative, flavor-symmetric window that survives both the LEP contact-interaction limits and the projected 14-TeV bounds; the paper itself points to multi-TeV vector-lepton mixing as one such corner, so a dedicated search closing that corner, or failing to, would settle the reach argument.","tokens_in":32207,"feed_emoji":"🧲","tokens_out":3967,"duration_ms":68100,"temperature":0.7,"pith_summary":"The measured muon magnetic moment sits about three standard deviations above the standard-model prediction, $a_μ^{exp}-a_μ^{th}=(287±80)×10^{-11}$. The paper asks a sharp question: if that gap comes from new weakly coupled particles near the electroweak scale, which specific particles are still allowed by everything we have already measured, and can the LHC finish the job? Rather than committing to one model, the authors enumerate every minimal addition of one or two fields with spin 0, $1/2$, or 1 and weak isospin up to one, compute each one-loop contribution to $a_μ$, and discard the cases that come out negative or too small. The survivors are then confronted with LEP precision data and with recast 8-TeV ATLAS and CMS searches. The payoff is a shortlist with mass bounds in the few-hundred-GeV range and projections near half a TeV to nearly a TeV for the 14-TeV run.","feed_headline":"LHC data already rules out some muon g-2 explanations","feed_subtitle":"A field-by-field sweep of new particles that could explain the muon's magnetic moment, and what 14 TeV can close.","key_machinery":"The load-bearing device is an exhaustive enumeration: every assignment of spin (0, $1/2$, 1) and weak isospin (singlet, doublet, triplet) to one or two new fields, with the couplings to muons that gauge invariance and the standard-model Higgs allow. Each case is reduced to a single number by projecting the one-loop $μ→μγ$ amplitude onto the magnetic form factor at zero momentum transfer, expanding in $m_μ$, and cross-checking with two independent computer implementations. The result is expressed as a required range of coupling over mass, typically $g/M$ or $Y/M$ between about 0.004 and 0.010 GeV$^{-1}$, which translates directly into a preferred mass window once perturbativity caps the coupling at $√{4π}$. Minimal flavor violation is the second piece of machinery: it is what keeps $μ→eγ$ and the muon mass under control, and it is what dictates how the new fermions are produced and how they decay, so that the recast of the experimental searches is well defined.","core_discovery":"The paper's claim is that the connection between the muon anomaly and collider data can be made model-independent enough to be decisive. Of the many candidate fields, most fail on their own: a neutral vector boson, a scalar doublet, and a scalar triplet are excluded or give the wrong sign, and single vector-like fermions are either negative or too small once Z-pole mixing limits are applied. Only a charged vector boson with right-handed couplings survives as a one-field explanation. Two mixing vector leptons can work, but only in a flavor scenario where the mixing among the new fermions is unconstrained, and then the viable masses run into the multi-TeV region the LHC cannot reach. The interesting cases are therefore two fields of different spin, and there the existing 8-TeV data already bite: the scalar-doublet-plus-fermion-doublet and scalar-doublet-plus-adjoint-fermion scenarios are excluded at two $\\sigma$, with bounds such as $M_{φ_D}>395$ GeV, $M_{φ_A}>456$ GeV, $M_{ψ_D}>296$ GeV, and $M_V>398$ GeV. Projecting to 14 TeV with 300 fb$^{-1}$ pushes these to roughly 660, 760, 510, and 676 GeV, which the authors argue closes almost every remaining scenario. A secondary contribution is a set of general one-loop four-lepton contact-interaction bounds from LEP, applicable to any coupling of a lepton to two new weakly coupled fields.","pith_inferences":["Because every mass bound scales with the assumed branching fractions, a discovery in a decay channel not listed in the paper's table would shift the quoted bounds by tens of GeV and could reopen the marginal scenarios; the authors say as much, but the size of the effect is worth tracking explicitly.","The 14-TeV projections assume selection efficiencies carry over unchanged from 8 TeV; if multi-lepton triggers and background rejection improve as they typically do, the real reach is likely to exceed the quoted 0.5 to 0.9 TeV rather than fall short of it.","The same enumeration could be run in reverse as a discovery template: an excess in a specific final state would single out one row of the table, turning a null-search program into a particle-identification scheme.","The paper's treatment of the electron magnetic moment as a constraint rather than a target suggests that improved electron $g-2$ measurements would squeeze the same parameter space from below, independently of collider reach."],"forward_implications":["If the anomaly is real and the new physics is perturbative, at least one new particle should sit within a few hundred GeV, so a 14-TeV run with hundreds of inverse femtobarns should either produce a multi-lepton excess or close the minimal explanations.","Any future multi-lepton excess at the LHC can be matched against the paper's table of viable spin and isospin assignments and their predicted mass orderings.","The one-loop four-lepton contact-interaction limits give a general constraint on any lepton coupling to two new fields, usable in models outside the specific list tabulated here.","A confirmed deviation in the electron magnetic moment of the size implied by the flavor-symmetric relation $δa_e/δa_μ=m_e^2/m_μ^2$ would remove the low-mass vector-lepton mixing window.","The negative results are as useful as the positive ones: a confirmed muon anomaly would count against type-II seesaw scalars and simple neutral vector bosons as its source."],"supporting_citations":[{"why":"Supplies the Brookhaven E821 measurement of the muon magnetic moment that defines the discrepancy.","marker":"[2]"},{"why":"Supplies the standard-model prediction and the numerical value $(287±80)×10^{-11}$ used as the target throughout.","marker":"[3]"},{"why":"Supplies the effective-operator relation between $a_μ$ and $μ→eγ$ that motivates the minimal-flavor-violation assumption.","marker":"[10]"},{"why":"Supplies the LEP four-lepton contact-interaction limits used to exclude neutral vector bosons and scalar doublets and to bound loop-level couplings.","marker":"[16]"},{"why":"Supplies the Z-pole bounds on mixing between standard-model leptons and vector leptons, which kill the single-fermion scenarios.","marker":"[20]"},{"why":"Supplies the ATLAS three-lepton plus missing-energy search recast into the scalar-doublet and scalar-triplet mass bounds.","marker":"[23]"},{"why":"Supplies the ATLAS four-lepton search recast into the vector-fermion and vector-boson mass limits.","marker":"[25]"},{"why":"Supplies the CMS slepton search recast into the $M_V>398$ GeV bound on charged vector bosons.","marker":"[24]"},{"why":"Supplies the procedure used to extrapolate 8-TeV searches to 14-TeV projections.","marker":"[28]"}],"fun_headline_variants":["8-TeV LHC data already excludes two-field muon g-2 models","14-TeV LHC could close nearly every muon g-2 scenario","Field-by-field sweep narrows muon g-2 explanations at the LHC","Only a charged vector boson survives as a one-field muon g-2 fix","LEP Z-pole limits undercut vector-like fermion muon g-2 fixes"],"cache_read_input_tokens":0,"weakest_assumption_plain":"Every mass bound assumes each new particle decays only through the channels listed in the paper's summary table, with the stated branching fractions; the authors acknowledge that any additional decay mode would drain the signal and weaken the limits.","fun_headline_variants_meta":{"raw":{"variants":["8-TeV LHC data already excludes two-field muon g-2 models","14-TeV LHC could close nearly every muon g-2 scenario","Field-by-field sweep narrows muon g-2 explanations at the LHC","Only a charged vector boson survives as a one-field muon g-2 fix","LEP Z-pole limits undercut vector-like fermion muon g-2 fixes"]},"model":"selfhosted/deepseek-v4.1-flash","effort":"low","attempts":1,"cost_usd":0.0,"raw_usage":{"total_tokens":1379,"prompt_tokens":1049,"completion_tokens":330,"prompt_tokens_details":null,"completion_tokens_details":{"reasoning_tokens":235}},"tokens_in":1049,"tokens_out":330,"duration_ms":5272,"image_pages":[],"temperature":1.0,"reasoning_budget":50,"reasoning_tokens":235,"transport_provider":"selfhosted","cache_read_input_tokens":0,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-10-29T06:25:11.012456+00:00","model_set":{"reader":"selfhosted/deepseek-v4.1-flash"},"falsifier":"The claim would be broken by exhibiting a parameter point inside the perturbative, flavor-symmetric window that survives both the LEP contact-interaction limits and the projected 14-TeV bounds; the paper itself points to multi-TeV vector-lepton mixing as one such corner, so a dedicated search closing that corner, or failing to, would settle the reach argument.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the Brookhaven E821 measurement of the muon magnetic moment that defines the discrepancy."},{"cited_title":"The muon g−2","cited_arxiv_id":"0902.3360","evidence_quote":"Supplies the standard-model prediction and the numerical value $(287±80)×10^{-11}$ used as the target throughout."},{"cited_title":"Minimal Flavor Violation in the Lepton Sector","cited_arxiv_id":"hep-ph/0507001","evidence_quote":"Supplies the effective-operator relation between $a_μ$ and $μ→eγ$ that motivates the minimal-flavor-violation assumption."},{"cited_title":"A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model","cited_arxiv_id":"hep-ex/0612034","evidence_quote":"Supplies the LEP four-lepton contact-interaction limits used to exclude neutral vector bosons and scalar doublets and to bound loop-level couplings."},{"cited_title":"Effects of new leptons in Electroweak Precision Data","cited_arxiv_id":"0803.4008","evidence_quote":"Supplies the Z-pole bounds on mixing between standard-model leptons and vector leptons, which kill the single-fermion scenarios."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the ATLAS three-lepton plus missing-energy search recast into the scalar-doublet and scalar-triplet mass bounds."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the ATLAS four-lepton search recast into the vector-fermion and vector-boson mass limits."},{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Supplies the CMS slepton search recast into the $M_V>398$ GeV bound on charged vector bosons."},{"cited_title":"Projected Performance of an Upgraded CMS Detector at the LHC and HL-LHC: Contribution to the Snowmass Process","cited_arxiv_id":"1307.7135","evidence_quote":"Supplies the procedure used to extrapolate 8-TeV searches to 14-TeV projections."}],"review_version":1}