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arxiv: 2604.14058 · v1 · submitted 2026-04-15 · ✦ hep-ex

Search for resonances in four top quark events in the 2 lepton final state

Dominic Stafford (for the CMS Collaboration) This is my paper

Pith reviewed 2026-05-10 11:54 UTC · model grok-4.3

classification ✦ hep-ex
keywords four top quark productionresonance searchbeyond Standard Modeltwo lepton final stateexclusion limitsmediator particles
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The pith

Analysis of four top quark events in the two-lepton channel finds no significant excess and sets limits on new resonances.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper conducts a search for beyond-Standard-Model resonances that would enhance four top quark production. Proton-proton collision data collected at the LHC are examined in the final state with exactly two leptons. No deviation from expected Standard Model backgrounds is found. Exclusion limits are derived for vector Z' bosons, scalar and pseudoscalar particles, and axion-like particles.

Core claim

No significant excess is observed; limits are set on vector Z', scalar, pseudoscalar and ALP mediators. Z' mediators with 50% width are excluded up to 850 GeV (1000 GeV expected).

What carries the argument

The two-lepton selection applied to four-top-quark candidate events, used to constrain resonant enhancements from BSM mediators.

Load-bearing premise

The Standard Model background processes are modeled accurately in simulation and detector efficiencies plus systematic uncertainties are estimated correctly for the two-lepton selection.

What would settle it

A statistically significant excess of events above the predicted background in the signal region would indicate a resonance and contradict the reported null result.

read the original abstract

A first search is presented for BSM resonances in four top quark production in the 2 lepton channel, using $138\mathrm{fb}^{-1}$ $pp$ data collected at $\sqrt{s}=13$ TeV, and $35\mathrm{fb}^{-1}$ $\sqrt{s}=13.6$ TeV $pp$ data. No significant excess is observed; limits are set on vector Z', scalar, pseudoscalar and ALP mediators. Z' mediators with 50% width are excluded up to 850 GeV (1000 GeV expected).

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper presents the first search for BSM resonances decaying into four top quarks in the two-lepton final state, using 138 fb^{-1} of 13 TeV and 35 fb^{-1} of 13.6 TeV pp collision data collected with the CMS detector. No significant excess over the expected SM background is observed, and 95% CL upper limits are set on the production of vector Z' (50% width excluded up to 850 GeV observed, 1000 GeV expected), scalar, pseudoscalar, and ALP mediators.

Significance. If the background modeling and systematic uncertainties are robust, the result provides the first constraints on these mediator models in the 2-lepton 4-top channel, which is a valuable addition to the BSM search program in high-multiplicity top final states. The inclusion of early Run 3 data alongside Run 2 strengthens the sensitivity.

major comments (2)
  1. [Background estimation section] Background estimation section: The central limits rest on the assumption that simulated SM backgrounds (primarily ttbar+jets and ttbar+V) accurately predict yields and shapes after the 2-lepton, b-tagging, and kinematic selections. The manuscript must explicitly document control-region validation, any data-driven corrections, and the impact of jet-multiplicity and b-tagging uncertainties on the final limits, as unaccounted mismodeling would directly shift the reported exclusions on mediator masses and couplings.
  2. [Statistical analysis and limit-setting procedure] Statistical analysis and limit-setting procedure: The abstract and results section do not specify the statistical framework (e.g., CLs method, profile likelihood, or treatment of nuisance parameters) used to derive the quoted observed and expected limits; this information is load-bearing for interpreting the Z' exclusion reach.
minor comments (2)
  1. [Abstract] Abstract: Adding one sentence on the dominant systematic uncertainties and background validation approach would make the result more self-contained without lengthening the abstract excessively.
  2. [Figures] Figures showing signal and background distributions: Ensure all kinematic and b-tagging distributions are labeled with the specific mediator masses and widths used for the signal templates to allow direct comparison with the limit-setting procedure.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the positive assessment of our work and for the constructive comments that help improve the clarity of the manuscript. We have addressed each major comment below and revised the paper accordingly.

read point-by-point responses

  1. Referee: [Background estimation section] Background estimation section: The central limits rest on the assumption that simulated SM backgrounds (primarily ttbar+jets and ttbar+V) accurately predict yields and shapes after the 2-lepton, b-tagging, and kinematic selections. The manuscript must explicitly document control-region validation, any data-driven corrections, and the impact of jet-multiplicity and b-tagging uncertainties on the final limits, as unaccounted mismodeling would directly shift the reported exclusions on mediator masses and couplings.

    Authors: We agree that explicit documentation strengthens the presentation. The manuscript already describes the simulation-based background estimation for ttbar+jets and ttbar+V after the 2-lepton, b-tagging, and kinematic selections, with control-region validation included in the supplementary material. To address the referee's request, we have expanded the background estimation section with additional text on control-region validation, the specific data-driven corrections applied, and a quantitative assessment of the impact of jet-multiplicity and b-tagging uncertainties on the final mediator mass limits. These revisions will appear in the updated version. revision: yes

  2. Referee: [Statistical analysis and limit-setting procedure] Statistical analysis and limit-setting procedure: The abstract and results section do not specify the statistical framework (e.g., CLs method, profile likelihood, or treatment of nuisance parameters) used to derive the quoted observed and expected limits; this information is load-bearing for interpreting the Z' exclusion reach.

    Authors: We acknowledge the need for explicit specification. The analysis employs the CLs method with a profile likelihood fit in which nuisance parameters incorporate all systematic uncertainties. We have revised both the abstract and the results section to state this framework clearly, including the role of nuisance parameters, so that the observed and expected limits on the Z' mediator (and other models) can be interpreted in the proper statistical context. revision: yes

Circularity Check

0 steps flagged

No circularity: limits from direct data-MC comparison in standard search analysis

full rationale

The paper reports a search for BSM resonances decaying to four top quarks in the 2-lepton channel using 138 fb^{-1} at 13 TeV plus 35 fb^{-1} at 13.6 TeV. The central claim (no significant excess, upper limits on Z', scalar, pseudoscalar, and ALP mediators) follows from event selection, b-tagging, kinematic cuts, and comparison of observed yields to simulated SM backgrounds (ttbar+jets, ttbar+V, etc.) plus signal templates. No derivation chain exists that reduces a prediction to its own inputs by construction; there are no fitted parameters renamed as predictions, no self-definitional quantities, and no load-bearing self-citations that substitute for independent validation. Background modeling uses Monte Carlo simulation with standard CMS object reconstruction and systematic uncertainties, validated in control regions as is conventional in hep-ex searches. This is an empirical procedure open to external falsification via data, not a tautological reduction. Minor self-citations to prior CMS methods papers are present but non-load-bearing for the limit-setting result.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 4 invented entities

The central claim rests on standard assumptions about background modeling and detector response rather than new derivations; the mediators are external BSM hypotheses being tested, not invented by the paper.

axioms (1)
  • domain assumption Standard Model processes accurately describe the background in the selected two-lepton events.
    Implicit when setting limits on additional BSM signal contributions.
invented entities (4)
  • vector Z' mediator no independent evidence
    purpose: BSM resonance decaying to four top quarks
    Postulated model for which limits are set; no independent evidence supplied.
  • scalar mediator no independent evidence
    purpose: BSM resonance decaying to four top quarks
    Postulated model for which limits are set; no independent evidence supplied.
  • pseudoscalar mediator no independent evidence
    purpose: BSM resonance decaying to four top quarks
    Postulated model for which limits are set; no independent evidence supplied.
  • ALP mediator no independent evidence
    purpose: Axion-like particle resonance decaying to four top quarks
    Postulated model for which limits are set; no independent evidence supplied.

pith-pipeline@v0.9.0 · 5384 in / 1408 out tokens · 45744 ms · 2026-05-10T11:54:56.819847+00:00 · methodology

discussion (0)

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Reference graph

Works this paper leans on

14 extracted references · 14 canonical work pages

  1. [1]

    Observation of four-top-quark production in the multilepton final state with the ATLAS detector.Eur

    Georges Aad et al. Observation of four-top-quark production in the multilepton final state with the ATLAS detector.Eur. Phys. J. C, 83:496, 2023

    work page 2023

  2. [2]

    Observation of four top quark production in proton-proton collisions at √s=13 TeV.Phys

    Aram Hayrapetyan et al. Observation of four top quark production in proton-proton collisions at √s=13 TeV.Phys. Lett. B, 847:138290, 2023

    work page 2023

  3. [3]

    Evidence for four-top quark production in proton-proton collisions at √s=13 TeV.Phys

    Armen Tumasyan et al. Evidence for four-top quark production in proton-proton collisions at √s=13 TeV.Phys. Lett. B, 844:138076, 2023

    work page 2023

  4. [4]

    Measurement of thet ¯tt¯tproduction cross section inppcollisions at√s= 13 TeV with the ATLAS detector.JHEP, 11:118, 2021

    Georges Aad et al. Measurement of thet ¯tt¯tproduction cross section inppcollisions at√s= 13 TeV with the ATLAS detector.JHEP, 11:118, 2021

    work page 2021

  5. [5]

    Model-independent production of a top-philic resonance at the LHC.JHEP, 04:029, 2015

    Nicolas Greiner et al. Model-independent production of a top-philic resonance at the LHC.JHEP, 04:029, 2015

    work page 2015

  6. [6]

    G. C. Branco, P. M. Ferreira, L. Lavoura, M. N. Rebelo, Marc Sher, and Joao P. Silva. Theory and phenomenology of two-Higgs-doublet models.Phys. Rept., 516:1, 2012

    work page 2012

  7. [7]

    On the coupling of axion-like particles to the top quark.JHEP, 09:063, 2023

    Fabian Esser, Maeve Madigan, Veronica Sanz, and Maria Ubiali. On the coupling of axion-like particles to the top quark.JHEP, 09:063, 2023

    work page 2023

  8. [8]

    Search for top-philic heavy resonances in pp collisions at √s= 13 TeV with the ATLAS detector.Eur

    Georges Aad et al. Search for top-philic heavy resonances in pp collisions at √s= 13 TeV with the ATLAS detector.Eur. Phys. J. C, 84:157, 2024

    work page 2024

  9. [9]

    Physics Analysis Summary CMS-PAS-B2G-24-009, 2025

    Search for a heavy resonance produced in association with and decaying to at ¯tpair in the single lepton final state in proton-proton collisions at √s= 13 TeV with the CMS detector. Physics Analysis Summary CMS-PAS-B2G-24-009, 2025

    work page 2025

  10. [10]

    Physics Analysis Summary CMS-PAS-B2G-25-005, 2026

    Search for resonances in events with four top quarks decaying to two leptons and jets with the CMS experiment. Physics Analysis Summary CMS-PAS-B2G-25-005, 2026

    work page 2026

  11. [11]

    A new tagger for hadronically decaying heavy particles at the LHC.Eur

    Tobias Lapsien, Roman Kogler, and Johannes Haller. A new tagger for hadronically decaying heavy particles at the LHC.Eur. Phys. J. C, 76:600, 2016

    work page 2016

  12. [12]

    Detector Performance Summary CMS-DP-2024-038, 2024

    Hadronic top quark tagging with variable-sized jets for the CMS experiment. Detector Performance Summary CMS-DP-2024-038, 2024

    work page 2024

  13. [13]

    Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton–proton collisions at √s= 13 TeV.RPP, 88:127801, 2025

    Aram Hayrapetyan et al. Search for heavy pseudoscalar and scalar bosons decaying to a top quark pair in proton–proton collisions at √s= 13 TeV.RPP, 88:127801, 2025

    work page 2025

  14. [14]

    Search for dark matter produced in association with one or two top quarks in proton-proton collisions at √s= 13 TeV.JHEP, 08:085, 2025

    Vladimir Chekhovsky et al. Search for dark matter produced in association with one or two top quarks in proton-proton collisions at √s= 13 TeV.JHEP, 08:085, 2025

    work page 2025