Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

CMS Collaboration

REVIEW 2 major objections 2 minor 1 cited by

Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV

T0 review · 2 major / 2 minor · reviewed 2026-07-14 · grok-4.5

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Pith's one-line read No excess of soft unclustered energy patterns with W or Z bosons in 138 fb^{-1} of LHC data; limits set on Higgs-to-SUEP decays.

desk verdict Standard CMS first-look null result on VH-associated Higgs o SUEP in leptonic + soft high-multiplicity tracks; useful limits and reinterpretation material, but abstract-only so methods stay unaudited. read the letter →

arxiv 2604.05996 v2 pith:IQGF5EGH submitted 2026-04-07 hep-ex

CMS Collaboration This is my paper · ORCID

classification hep-ex

keywords softunclusteredenergypatternSUEPHiggsbosonWZassociatedproductionLHCCMS

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

This CMS search looks for a Higgs boson produced together with a W or Z and decaying into a soft unclustered energy pattern (SUEP): a high-multiplicity spray of low-momentum charged particles that does not form ordinary jets. Using the full Run-2 proton-proton data set of 138 fb^{-1} at 13 TeV, the analysis selects leptonic W or Z decays and then examines the associated soft-track multiplicity for the first time. No significant excess above the standard-model background is observed. The paper therefore places upper limits on the production cross section of a Higgs boson that decays to a SUEP, covering a range of the model parameters that control the softness and multiplicity of the pattern. Auxiliary material is released so that other interpretations of the same final state can be tested.

What carries the argument

The experimental signature is a leptonically decaying W or Z boson accompanied by an anomalously large number of soft charged tracks that do not form collimated jets. Backgrounds are estimated from standard-model processes in the same high-multiplicity, low-momentum phase space; any excess would appear as a deviation from that estimate.

What would settle it

A statistically significant excess of high-multiplicity soft charged tracks above the estimated standard-model background in the leptonic W/Z-associated sample, or a measured Higgs-to-SUEP cross section lying above the reported exclusion limits for the same model parameters.

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Extended reading notes

Core claim

In 138 fb^{-1} of 13 TeV pp collisions, events containing a leptonic W or Z boson plus a high multiplicity of low-momentum charged particles show no significant excess over the standard-model expectation; consequently upper limits are set on the cross section for Higgs production followed by decay to a soft unclustered energy pattern across a range of SUEP model parameters.

Load-bearing premise

The standard-model backgrounds that produce high-multiplicity, low-momentum charged particles next to a leptonic W or Z are modeled accurately enough that a genuine SUEP signal would stand out as a clear excess.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

This is a clean first experimental look at SUEP in the VH channel with leptonic W/Z tags plus a high multiplicity of soft charged tracks. CMS finds no excess over SM expectation in 138 fb^{-1} and sets cross-section limits across a range of SUEP parameters, with material for reinterpretation. That is exactly what you want from this kind of search: a previously unprobed final state, a null result stated plainly, and limits that other people can actually use.

What is new is the final-state choice itself. Soft unclustered energy patterns have been discussed, but pairing them with a clean leptonic vector boson and high-multiplicity low-pT tracks is a genuine first application of existing collider tools to that signature. The analysis is data-driven in the usual CMS sense—compare observed events to SM background and set limits on an external signal model—so circularity is not a concern. Self-citation and free parameters in the SUEP model (dark temperature, meson mass scale, etc.) are expected and not a flaw here.

The soft spot is the one the reader already flagged and the stress-test correctly refuses to inflate: soft-track reconstruction efficiency and background modeling in the high-multiplicity, low-momentum region are load-bearing, and we cannot audit them from the abstract. That is an information boundary, not an internal contradiction or a hidden assumption we can falsify. CMS analyses of this type are generally careful; I would expect the full paper to document the usual suite of control regions, efficiency measurements, and systematics. Until then, treat the soundness score as provisional.

Who this is for: people working on exotic Higgs decays, dark-sector phenomenology, or soft-track reconstruction at the LHC. It is not paradigm-shifting, but it is solid experimental coverage of a previously empty corner. I would bring it to a reading group if someone is already thinking about SUEP or soft dark showers; otherwise it is a useful reference rather than a must-read. It clearly deserves a serious referee rather than a desk reject—standard CMS search with a new final state and public reinterpretation material. I would cite the limits if I needed a VH o SUEP constraint in the next year.

Referee Report

2 major / 2 minor

Summary. The manuscript reports a CMS search for a Higgs boson produced in association with a W or Z boson and decaying to a soft unclustered energy pattern (SUEP), using 138 fb^{-1} of 13 TeV pp collision data collected in 2016–2018. Final states with a leptonic W or Z decay accompanied by a high multiplicity of low-momentum charged particles are explored for the first time. No significant excess over the Standard Model background expectation is observed. Limits are set on the production cross section of a Higgs boson that decays to a SUEP for a range of SUEP model parameters, and material is provided to facilitate further interpretation.

Significance. If the analysis holds under full scrutiny, this is a first exploration of VH-associated Higgs→SUEP signatures in a soft, high-multiplicity charged-particle final state, delivering null-result limits and reinterpretation material for confining dark-sector models. That is a useful addition to the exotic Higgs and hidden-sector program at the LHC. The abstract-level claim form (no excess; parameter-dependent cross-section limits; reinterpretation material) is the appropriate deliverable for such a search. Soft-track reconstruction and background control in this phase space are the load-bearing experimental ingredients that determine whether the result is robust.

major comments (2)

[Abstract] Abstract (results claim): The statement of no significant excess over the SM background expectation is load-bearing and depends on accurate modeling of SM backgrounds in the high-multiplicity, low-momentum charged-particle region associated with leptonic W/Z decays. Soft-track reconstruction efficiency, pileup treatment, and background estimation/validation in this phase space cannot be audited from the abstract alone. The full manuscript must document control regions, efficiency measurements, and systematic uncertainties with enough detail for independent assessment; without that, the null-result claim cannot be certified.
[Abstract] Abstract (limits and reinterpretation): Limits are reported for a range of SUEP model parameters, with material for further interpretation. Signal simulation, acceptance definition, statistical procedure, and the exact parameter grid are not available in the abstract. These elements are load-bearing for the usability of the limits; the full text must specify them so that the cross-section limits and reinterpretation material can be checked and reused.

minor comments (2)

[Abstract] Abstract: The phrase “for a range of parameters of the SUEP model” should, in the full paper, be paired with an explicit list or table of the scanned parameters (e.g. dark temperature, dark meson mass scale) so that the scope of the limits is unambiguous at first reading.
[Abstract] Abstract: “Material is provided to facilitate further interpretation of the results” is welcome but vague; the full manuscript should state what is released (e.g. efficiency maps, simplified-likelihood inputs, HEPData tables) in the abstract or introduction for discoverability.

Circularity Check

0 steps flagged · score 0.0 of 10

No circularity: standard CMS null-result search with external signal model and data-driven SM comparison.

full rationale

This is an abstract-only review of a CMS Collaboration experimental search. The claimed result is a null finding (no significant excess over the Standard Model background expectation) plus upper limits on the production cross section of a Higgs boson decaying to a SUEP for a range of external model parameters, with material provided for reinterpretation. Nothing in the abstract indicates that the reported limits or null result are obtained by fitting a parameter to the same data and then re-presenting that fit as a prediction, by defining the signal in terms of the observed excess, by load-bearing self-citation of an unverified uniqueness theorem, or by renaming a known empirical pattern. The derivation chain is the ordinary experimental one: select final states with leptonic W/Z plus high-multiplicity low-momentum charged particles, compare observed yields to SM background expectation, and set limits on an external SUEP signal hypothesis. Residual risks (soft-track reconstruction, background modeling in this phase space) are ordinary experimental systematics and model-dependence, not circularity. Score 0 is the correct honest finding for a self-contained data-driven search against external benchmarks.

Assumptions & free parameters 1 free parameters · 3 assumptions · 0 invented entities

Abstract-only experimental search. The claim rests on standard LHC analysis assumptions (SM background modeling, detector response for soft tracks, SUEP signal model from prior theory literature) rather than free parameters fitted to force the null result. No new particles or forces are invented here; SUEP is an existing model being constrained. Free parameters of the SUEP model are scanned for limits, not fitted to manufacture the central claim.

free parameters (1)

SUEP model parameters (e.g. dark temperature, dark meson mass scale)
Abstract states limits are set 'for a range of parameters of the SUEP model.' These define signal hypotheses being constrained, not numbers fitted to produce the null result. Exact names and values are not given in the abstract.

assumptions (3)

domain assumption Standard Model background expectation in the high-multiplicity soft-track region with leptonic W/Z is accurately modeled.
Load-bearing for the 'no significant excess' statement in the abstract; without it the null claim is undefined.
domain assumption The SUEP signal model from prior literature correctly maps model parameters onto a high multiplicity of low-momentum charged particles.
The search targets that signature; mis-modeling would invalidate the interpretation of the limits.
domain assumption Soft charged-particle reconstruction and lepton identification efficiencies are sufficiently well understood for the claimed sensitivity.
Implicit in any CMS soft-track multiplicity analysis; not verifiable from the abstract.

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Cite this review

Pith. "Pith review of Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at $\sqrt{s}$ = 13 TeV." pith.science (2026). https://pith.science/paper/IQGF5EGH

@misc{pith2026260405996,
  author       = {Pith},
  title        = {Pith review of: Search for soft unclustered energy patterns produced in association with a W or Z boson in proton-proton collisions at $\sqrts$ = 13 TeV},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/IQGF5EGH}},
  note         = {Machine review of arXiv:2604.05996}
}

abstract

A search for a Higgs boson produced in association with a W or Z boson and decaying via a soft unclustered energy pattern (SUEP) is presented. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 138 fb$^{-1}$ collected between 2016 and 2018 at the LHC. Final states with a leptonic W or Z boson decay associated with a high multiplicity of low-momentum charged particles are explored for the first time. The results show no significant excess over the standard model background expectation. Limits are set on the production cross section of a Higgs boson that decays to a SUEP, for a range of parameters of the SUEP model. Material is provided to facilitate further interpretation of the results.

Figures

Figures reproduced from arXiv: 2604.05996 by the authors.

**Figure 2.** Distributions of n SUEP constituent in the extended ABCD subregions A–I in the PR-WH (upper) and PR-ZH (lower) regions, showing the observed data and the background predictions. The distribution is split into S SUEP boosted (p j 1 T ) bins for the WH (ZH) channel. The last n SUEP constituent bin includes the overflow events. The shaded bands indicate the uncertainties in the prediction, which are propagated to the … view at source ↗

**Figure 3.** Distributions of n SUEP constituent in the extended ABCD subregions A–I in the SR for the WH (upper) and ZH (lower) channels, showing the observed data, the predictions from the background-only fit, and several signal hypotheses with fully hadronic decays (B(A′ → π +π −) = 100%): mϕD = 4 GeV, TD = 8 GeV; mϕD = 3 GeV, TD = 3 GeV; and mϕD = 4 GeV, TD = 1 GeV. The distribution is split into S SUEP boosted (p j 1 T ) bi… view at source ↗

Figures from the paper (4 more)

**Figure 4.** Figure 4: Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to a [PITH_FULL_IMAGE:figures/full_fig_p011_4.png]

**Figure 5.** Figure 5: Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to a [PITH_FULL_IMAGE:figures/full_fig_p012_5.png]

**Figure 6.** Figure 6: Interpretation of the results for the decay of the 125 GeV Higgs boson mediator to [PITH_FULL_IMAGE:figures/full_fig_p013_6.png]

**Figure 7.** Figure 7: 95% CL upper limits on the signal yield from the model-agnostic fit for different [PITH_FULL_IMAGE:figures/full_fig_p014_7.png]

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Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Search for soft unclustered energy patterns containing muons in the final state in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
hep-ex 2026-05 unverdicted novelty 6.0 of 10

No significant excess observed in search for SUEP signatures with muons; exclusion limits set on mediator cross section times branching fraction down to 0.05 fb at 750 GeV.

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Reviewed July 14, 2026 · model on record in the stance chip above.