REVIEW
Dark Diffraction at LZ from a Screened Neutral Composite Baryon
High Energy Physics - Phenomenology · Submitted 22 Sep 2026 · 43 references
Pith's verdict: A careful, honest proof of principle for an elastic composite-DM explanation of the LZ 248 keV candidate: the four-term minimality result is real, but the quantitative node and sideband predictions rest on a hand-imposed part-in-10^5 cancellation that no dynamics enforces.
T0 · AI review
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Referee report
The paper
The paper claims
This paper argues that the 248 keV LZ recoil candidate can be explained elastically, by a screened composite dark-matter baryon whose charge form factor acts as a momentum-space band-pass filter, predicting diffraction nodes at fixed…
The reading
What carries the argument
The object that carries the argument is the dark charge form factor $F_D(q) = \sum_{i=1}^N Q_i \exp(-q^2 r_i^2/6)$, one Gaussian per charged constituent species, subject to neutrality $\sum_i Q_i = 0$; this is the paper's momentum-space band-pass filter. A Descartes-type rule for exponential sums limits $N$ terms to at most $N-2$ finite nodes, and the two-term bound $|F_2(q)|/|F_2(q_\star)| \ge (q/q_\star)^2$ rules out two terms outright. The benchmark's distinctive feature is a cancellation to one part in $10^5$ between constituent Gaussians that holds $|F_D|$ below $10^{-4}$ over the screened band, which is what allows the recoil spectrum to peak near the candidate while placing only a few percent of the rate below 55 keV.
Extended reading notes
Core claim
The central claim is that the LZ 248 keV event admits an elastic explanation through a strongly screened composite-baryon form factor. Concretely, the fewest independent Gaussian terms needed to reproduce a hard recoil spectrum at LZ is four: two terms cannot suppress the low-momentum amplitude better than the pure $q^2$ law, and three terms peak at 170 keV with too little rate near the candidate, while the four-term benchmark fixes a definite pair of momentum-space nodes at $q_1 \simeq 0.084$ GeV and $q_2 \simeq 0.166$ GeV, corresponding to xenon recoil energies of 29 and 113 keV. A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete current through a neutral bosonic four-quark baryon, though the authors emphasize that it motivates rather than derives the benchmark radii. The transferable predictions are the nodes, which should appear at the same momenta in every target with recoil energies scaling as $1/m_A$, and a second recoil lobe beyond the region of interest, capped by the kinematic endpoint, whose population would bound the baryon mass.
Load-bearing premise
The load-bearing premise is that the dark form factor can genuinely vanish over a wide low-momentum band — a cancellation to one part in $10^5$ between constituent Gaussians realized by hand-chosen radii — and the paper does not construct dynamics that enforce this sum rule; if no such dynamics can coexist with fermi-sized charge radii inside a 200 GeV baryon, the benchmark and its node predictions fail.
Editorial extensions
If this is right
- A single elastic composite-baryon current can account for the 248 keV LZ event without inelastic mass splittings or boosted populations, provided four independent Gaussian terms suffice.
- Two momentum-space nodes are predicted at fixed momenta, appearing at 29 and 113 keV in xenon, 95 and 370 keV in argon, 52 and 203 keV in germanium, and 21 and 80 keV in tungsten — a common momentum-space structure that neither a node-free form factor nor an inelastic splitting produces.
- A second recoil lobe grows beyond the region of interest, capped by the kinematic endpoint, so a joint signal-region and sideband analysis would bound the baryon mass, the benchmark's high-energy population rising from 0.5 true recoils at 150 GeV to 7.5 at 1 TeV.
- The low-energy stop band suppresses the rate below 55 keV to a few percent of the total, so the absence of a conventional WIMP-like low-energy population is expected rather than in tension.
Reading between the lines
- If the nodes are real, tungsten and argon provide the cleanest independent tests: argon can reach the first node without ever reaching the candidate momentum, and tungsten's nodes at 21 and 80 keV sit away from its own Helm minima, making each a fairly background-free check of the band-pass hypothesis.
- The one-part-in-$10^5$ cancellation is the natural place for new dark-flavor dynamics: if a symmetry or selection rule can enforce $F_D \approx 0$ over a broad band while breaking controllably to generate the second node, that sum rule would be a more fundamental statement than any single benchmark.
- A cross-target test is the sharpest discriminator against inelastic interpretations, since the $1/m_A$ node scaling is a distinct fingerprint whereas inelastic splittings tie recoil energies to the reduced-mass relation; measuring nodes in two targets at the predicted momenta would separate the mechanisms even without a second event.
- Because the high-energy population grows steeply with baryon mass, an empty sideband would act as a mass bound and force the screening cancellation to be even more severe at fixed coupling, tightening the theoretical cost the paper itself flags.
Original abstract
The LUX-ZEPLIN (LZ) experiment recently reported a nuclear-recoil-like candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}$ keV. We show that such an energetic recoil can arise from the elastic form factor of composite dark matter, without invoking an inelastic mass splitting or a boosted population. A neutral baryon of $N$ dark quarks can have a charge form factor that is suppressed at low momentum transfer but recovers at higher momentum transfer, providing a momentum-space band-pass filter. Modeling the form factor with one Gaussian per charged constituent species, we prove that two terms cannot produce a hard recoil spectrum and find that three yield too few events in the LZ signal window, while four suffice. A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete realization through a neutral bosonic baryon made of four dark quarks. For a 200 GeV benchmark normalized to one accepted event, we predict approximately 1.5 true recoils beyond the current LZ region of interest. The form factor also produces diffraction nodes at fixed momentum transfers, placing them at recoil energies that scale as $1/m_A$ across target nuclei.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The LUX-ZEPLIN (LZ) experiment recently reported a nuclear-recoil-like candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}$ keV. We show that such an energetic recoil can arise from the elastic form factor of composite dark matter, without invoking an inelastic mass splitting or a boosted population. A neutral baryon of $N$ dark quarks can have a charge form factor that is suppressed at low momentum transfer but recovers at higher momentum transfer, providing a momentum-space band-pass filter. Modeling the form factor with one Gaussian per charged constituent species, we prove that two terms cannot produce a hard recoil spectrum and find that three yield too few events in the LZ signal window, while four suffice. A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete realization through a neutral bosonic baryon made of four dark quarks. For a 200 GeV benchmark normalized to one accepted event, we predict approximately 1.5 true recoils beyond the current LZ region of interest. The form factor also produces diffraction nodes at fixed momentum transfers, placing them at recoil energies that scale as $1/m_A$ across target nuclei.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The LUX-ZEPLIN (LZ) experiment recently reported a nuclear-recoil-like candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}$ keV. | background 0.99 | 0.08 | 0.03 | asserted 1.00 |
| s1 | We show that such an energetic recoil can arise from the elastic form factor of composite dark matter, without invoking an inelastic mass splitting or a boosted population. | contribution 0.60 | 0.91 | 0.79 | asserted 0.98 |
| s2 | A neutral baryon of $N$ dark quarks can have a charge form factor that is suppressed at low momentum transfer but recovers at higher momentum transfer, providing a momentum-space band-pass filter. | contribution 0.47 | 0.54 | 0.23 | asserted 0.87 |
| s3 | Modeling the form factor with one Gaussian per charged constituent species, we prove that two terms cannot produce a hard recoil spectrum and find that three yield too few events in the LZ signal window, while four suffice. | result 0.79 | 0.93 | 0.24 | asserted 1.00 |
| s4 | A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete realization through a neutral bosonic baryon made of four dark quarks. | contribution 0.68 | 0.64 | 0.07 | asserted 0.97 |
| s5 | For a 200 GeV benchmark normalized to one accepted event, we predict approximately 1.5 true recoils beyond the current LZ region of interest. | result 0.99 | 0.89 | 0.10 | asserted 0.91 |
| s6 | The form factor also produces diffraction nodes at fixed momentum transfers, placing them at recoil energies that scale as $1/m_A$ across target nuclei. | result 0.97 | 0.80 | 0.10 | asserted 1.00 |
What was examined, and what was not
- arXiv listing abstract v1
- full text
- figures and tables
- references and citing sentences
- relations to other papers
- P abstract
- S sections
- T body sentences
- C citations
- R cross-paper relations
Figures
Figures reproduced from arXiv:2609.25723 by the authors.
References
Discussion
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