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arxiv: 2506.09490 · v6 · submitted 2025-06-11 · ✦ hep-ph · hep-ex

Evidence for BSM spin 0 and spin 2 resonances at LHC Possible Interpretations

Alain Le Yaouanc , Fran\c{c}ois Richard This is my paper

Pith reviewed 2026-05-19 09:54 UTC · model grok-4.3

classification ✦ hep-ph hep-ex
keywords LHC resonancesbeyond Standard Modelspin-2 resonanceKaluza-Klein graviton650 GeVtensor resonancescalar resonancevector boson fusion
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The pith

LHC data shows excesses around 650 GeV that fit a single 20 GeV wide spin-2 resonance in electron pairs, photons and ZZ.

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

The paper examines nine statistically significant excesses in LHC collision data near 650 GeV across different decay channels. It assigns three of those channels to one resonance with spin 2 that is produced through vector boson fusion and matches the pattern expected for a Kaluza-Klein graviton. This leads to the further claim that the data contain the start of a predicted mass sequence of such tensor states, while other channels may point to scalar states. If the assignment holds, the pattern would imply both new particles and specific production and decay rates that future electron-positron machines could exploit at high rates.

Core claim

Nine statistically significant decay channels are observed in LHC data around a mass of 650 GeV. Three of them are interpreted as coming from a 20 GeV wide resonance observed in e+e−, 2 photons and ZZ which could be a J=2 Kaluza Klein graviton resonance called T690. This hypothesis is reinforced by noting that this signal is produced by VBF and it disappears in ZZ when treated as a scalar. Given that the six other excesses have poor mass resolution, one cannot exclude the presence of an additional wide scalar resonance called H650. Assuming a Randall Sundrum RS model, we conclude that LHC observes the predicted sequence T376, T690 and T1000. At variance with the RS model, T690 weakly couples

What carries the argument

The T690 assignment that links the electron-pair, diphoton and ZZ excesses to one 20 GeV wide J=2 state produced via vector boson fusion.

If this is right

  • Perturbative unitarity then requires additional resonances T++ decaying to W+W+ and T+ decaying to ZW that already appear indicated in the data.
  • With a branching ratio to electrons of roughly 0.25 percent the same states could be produced in large numbers at future electron-positron colliders.
  • The scalar states H650 and A490 can produce observable deficits rather than excesses in top-pair mass spectra through top-loop effects in gluon fusion.
  • The scalar resonances align with the triple-Higgs-doublet structure expected in certain extensions of the Higgs sector.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The weak coupling to gluons favors a composite interpretation over a pure extra-dimension model for T690.
  • Dedicated searches for the predicted charged resonances would provide an independent test of the unitarity argument.
  • Electron-positron machines could function as resonance factories for the full mass sequence if the electron branching ratio is confirmed.
  • Similar multi-channel excesses at other mass values could reveal an entire tower of related states.

Load-bearing premise

The nine observed excesses are produced by genuine new resonances rather than statistical fluctuations or inadequately modeled Standard Model backgrounds.

What would settle it

A combined fit to the ATLAS and CMS data that shows the electron-pair, diphoton and ZZ excesses cannot share a common 20 GeV width and vector-boson-fusion production mechanism would rule out the single T690 resonance.

read the original abstract

Nine statistically significant decay channels are observed in LHC data around a mass of 650 GeV. We interpret three of them as coming from a 20 GeV wide resonance observed in $e^+e^-$ , 2 photons and ZZ which could be a $J=2$ Kaluza Klein graviton resonance called T690 (T for tensor with J=2). This hypothesis is reinforced by noting that this signal is produced by VBF and it disappears in ZZ when treated as a scalar. Given that the six other excesses have poor mass resolution, one cannot exclude the presence of an additional wide scalar resonance called H650. Assuming a Randall Sundrum RS model, we conclude that LHC observes the predicted sequence T376, T690 and T1000. At variance with the RS model, T690 weakly couples to gluon pairs, suggesting a composite model interpretation. It does significantly couple to $e^+e^-$ which has implications for $e^+e^-$ colliders. Perturbative unitarity requirements predict $T^{++} \to W^+W^+$ and $T^+\to ZW$ resonances, again indicated by LHC data. Assuming BR($e^+e^-$ )$\sim$0.25%, deduced from ATLAS and CMS, this scenario offers excellent prospects for abundantly (Gigafactory) producing a sequence of narrow resonances at future $e^+e^-$ colliders. For heavy scalars, the situation is less clear. Following ATLAS and CMS, we expect that the top loop contribution to the gluon-gluon fusion mechanism ggF could produce a deficit rather than an excess in the mass distribution of top pairs, which prevents a standard estimate of the statistical significance for heavy resonances. It seems that the pseudo-scalar and scalar resonances A490 and H650, indicated by other channels, create observable deviations in the t t analyses presented by ATLAS and CMS. The scalar resonances seem to form the triple Higgs doublet structure predicted by Weinberg. The present note summarises these arguments and collects available indications in view of electing a future collider.

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

3 major / 2 minor

Summary. The manuscript claims that nine statistically significant decay channels observed in existing LHC data around 650 GeV provide evidence for BSM resonances. It interprets three of them (e+e−, γγ, ZZ) as arising from a single 20 GeV-wide J=2 Kaluza-Klein graviton resonance T690 produced via VBF, with the remaining six possibly indicating an additional wide scalar H650; this is said to match the RS-model sequence T376, T690, T1000 (with composite-model adjustments), yielding predictions for future e+e− colliders and perturbative unitarity requirements.

Significance. If the central interpretation were substantiated by rigorous statistical combination, the result would be highly significant as concrete evidence for specific BSM resonances with testable implications for e+e− colliders and deviations in tt̄ analyses. The paper correctly notes the potential for a triple-Higgs-doublet structure and the importance of VBF production, but these strengths are undermined by the lack of new data or combined fits.

major comments (3)
  1. [Abstract and T690 interpretation] Abstract and section on T690 assignment: the claim that three channels align as a single 20 GeV-wide J=2 resonance requires a joint likelihood or at least trials-factor-corrected combination of the nine uncombined excesses from separate ATLAS/CMS publications; none is presented, and mass-resolution limitations are acknowledged but not quantitatively propagated into the resonance hypothesis.
  2. [Branching ratio and collider prospects] Branching-ratio section: BR(e+e−) ∼ 0.25% is deduced from the identical ATLAS/CMS data used to identify the excesses, so the stated predictions for e+e− colliders and the distinction from RS-model expectations reduce to quantities fitted from the input observations rather than independent tests.
  3. [Production mechanism and spin assignment] VBF and scalar-vs-tensor discussion: the assertion that the signal is VBF-produced and disappears in ZZ when treated as scalar is not supported by re-derivation of significances or background modeling under a common resonance hypothesis across the referenced channels.
minor comments (2)
  1. [Notation] Notation for the ad-hoc resonances (T690, H650, T376, T1000) should be introduced with explicit definitions and mass/width values on first appearance.
  2. [References to LHC results] Each of the nine decay channels needs explicit citation to the specific ATLAS or CMS publication, including the reported local significance and mass window.

Simulated Author's Rebuttal

3 responses · 1 unresolved

We thank the referee for the careful and detailed review of our manuscript. Our work presents an interpretive analysis of publicly reported LHC excesses around 650 GeV, proposing a possible resonance interpretation. Below we address each major comment directly, clarifying the scope and limitations of the analysis while noting revisions where appropriate.

read point-by-point responses

  1. Referee: [Abstract and T690 interpretation] Abstract and section on T690 assignment: the claim that three channels align as a single 20 GeV-wide J=2 resonance requires a joint likelihood or at least trials-factor-corrected combination of the nine uncombined excesses from separate ATLAS/CMS publications; none is presented, and mass-resolution limitations are acknowledged but not quantitatively propagated into the resonance hypothesis.

    Authors: We agree that a formal joint likelihood or trials-factor-corrected combination would provide stronger statistical support. The excesses originate from independent ATLAS and CMS publications with differing selections, backgrounds, and resolutions, and the necessary covariance information for a combined fit is not publicly available. Our manuscript notes the mass coincidence and width consistency across channels as suggestive evidence rather than a definitive statistical claim. We have revised the abstract and T690 section to more explicitly state the interpretive nature of the hypothesis and added a quantitative discussion of how the reported mass resolutions accommodate a common 20 GeV-wide resonance. revision: partial

  2. Referee: [Branching ratio and collider prospects] Branching-ratio section: BR(e+e−) ∼ 0.25% is deduced from the identical ATLAS/CMS data used to identify the excesses, so the stated predictions for e+e− colliders and the distinction from RS-model expectations reduce to quantities fitted from the input observations rather than independent tests.

    Authors: The branching-ratio estimate is derived from the observed excesses to set the normalization scale for prospective rates at future colliders; this is a standard approach in phenomenological interpretations. The distinction from standard RS expectations arises from the data-driven observation of weak coupling to gluons (absence of corresponding excesses in gluon-initiated channels), which is independent of the BR(e+e−) normalization. The collider prospects are forward-looking predictions that can be tested with new data. We have revised the relevant section to clarify that these are estimates based on current observations intended to motivate future experimental tests rather than independent validations. revision: yes

  3. Referee: [Production mechanism and spin assignment] VBF and scalar-vs-tensor discussion: the assertion that the signal is VBF-produced and disappears in ZZ when treated as scalar is not supported by re-derivation of significances or background modeling under a common resonance hypothesis across the referenced channels.

    Authors: The VBF production inference follows from the pattern of observed excesses in channels sensitive to vector-boson fusion and their absence in gluon-fusion-dominated modes. The spin-2 preference is motivated by the consistency with ZZ and other channels under a tensor hypothesis versus the additional assumptions required for a scalar. A full re-derivation of significances and background modeling under a single common hypothesis would require reprocessing the original experimental data and is beyond the scope of this interpretive note. We have expanded the discussion in the revised manuscript to include more detail on the channel-dependent production mechanisms and the rationale for the tensor assignment while acknowledging the limitations of the current approach. revision: partial

standing simulated objections not resolved
  • A rigorous joint statistical combination of the nine excesses, which would require detailed likelihood functions and covariance information from the ATLAS and CMS collaborations that are not available in public data releases.

Circularity Check

1 steps flagged

BR(e+e−) extracted from input excesses; central interpretation remains data-driven collection rather than tautological derivation

specific steps
  1. fitted input called prediction [Abstract]
    "Assuming BR(e^+e^-)∼0.25%, deduced from ATLAS and CMS, this scenario offers excellent prospects for abundantly (Gigafactory) producing a sequence of narrow resonances at future e^+e^- colliders."

    The branching ratio is extracted from the same ATLAS/CMS data excesses that are interpreted as the T690 signal. The 'excellent prospects' statement therefore incorporates a parameter fitted directly from the input observations rather than an independent first-principles calculation.

full rationale

The paper collects reported excesses from separate ATLAS/CMS publications and assigns three channels to a single T690 resonance under a VBF production hypothesis. The only load-bearing fitted quantity is the branching ratio BR(e+e−)∼0.25% stated as 'deduced from ATLAS and CMS'. This value is used to project future collider yields but does not retroactively define the existence or mass alignment of the excesses themselves. No self-citation chain, uniqueness theorem, or ansatz is invoked to force the resonance assignment; the RS-model sequence is presented as an assumption rather than a derived necessity. The derivation chain therefore contains one minor fitted-input step but remains largely self-contained against external LHC publications.

Axiom & Free-Parameter Ledger

3 free parameters · 2 axioms · 3 invented entities

The central claim rests on several fitted parameters for resonance properties and multiple postulated new particles without independent evidence outside the fitted LHC excesses.

free parameters (3)
  • T690 mass = 650 GeV
    Chosen to align with position of observed excesses across channels
  • T690 width = 20 GeV
    Selected to describe the reported signal width
  • BR(e+e-) = ~0.25%
    Deduced from ATLAS and CMS data to match observed rates
axioms (2)
  • domain assumption The nine decay channels represent statistically significant signals from new resonances
    Invoked throughout the abstract to justify interpreting LHC data as BSM particles
  • domain assumption VBF production and disappearance under scalar hypothesis confirm J=2 assignment
    Used to reinforce the tensor resonance interpretation
invented entities (3)
  • T690 no independent evidence
    purpose: Spin-2 Kaluza-Klein graviton explaining e+e-, gamma-gamma and ZZ excesses
    Postulated to fit the three high-resolution channels
  • H650 no independent evidence
    purpose: Scalar resonance accounting for poorer-resolution excesses
    Introduced as possible additional state
  • T376 and T1000 no independent evidence
    purpose: Additional resonances completing the RS sequence
    Assumed from the model framework

pith-pipeline@v0.9.0 · 5921 in / 1761 out tokens · 69555 ms · 2026-05-19T09:54:02.971796+00:00 · methodology

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