REVIEW
Is the Light Neutralino Dark Matter Still Viable in the MSSM After the LZ-2024 Results?
High Energy Physics - Phenomenology · Submitted 7 Oct 2026 · 85 references
Pith's verdict: Solid envelope argument likely closes the h- and Z-funnel holes in the MSSM, but the headline 5.9/4.1 sigma numbers are a zero-background Poisson extrapolation and should be treated as recast estimates, not official LZ significances.
T0 · AI review
Why Pith says this
Highlight any text to comment on it.
Referee report
The paper
The paper claims
LZ-2024 data close the two remaining thermal windows for light neutralino dark matter in the MSSM, excluding them at one-sided significances above 5.9σ and 4.1σ.
The reading
What carries the argument
The central object is the one-to-one correspondence between the annihilation and scattering couplings of a nearly pure Bino: the $\tilde\chi_1^0\tilde\chi_1^0 h$ coupling $C_h$ governs both the s-channel annihilation that sets the relic density in the h-funnel and the spin-independent scattering cross section, while the $\tilde\chi_1^0\tilde\chi_1^0 Z$ coupling $C_Z$ plays the dual role in the Z-funnel for spin-dependent scattering. This identity converts the requirement that $\tilde\chi_1^0$ reproduce the measured $\Omega h^2$ into lower envelopes on $\sigma_{\rm SI}$ and $\sigma_{\rm SD}$, because the mediator's finite width and the thermal smearing of initial-state momenta keep the thermally averaged annihilation cross section finite. The quantitative work is done by 904 one-loop vertex diagrams that shift $\sigma_{\rm SI}$ by up to 50% and $\sigma_{\rm SD}$ by up to 30%, and by a background-free Poisson recast of LZ-2024 whose expected signal count, $N_{\rm ev} = 2.3\,[\sigma_{\rm SI}/\sigma_{\rm SI}^0 + \sigma_{\rm SD}/\sigma_{\rm SD}^0]\, \Omega h^2/0.12$, is calibrated to the published 90% C.L. reference cross sections.
Extended reading notes
Core claim
The paper aims to establish that the h-funnel and Z-funnel regions — the only non-coannihilation thermal production mechanisms for a sub-hundred-GeV $\tilde\chi_1^0$ in the MSSM with decoupled sfermions — are both excluded by the LZ-2024 exposure. The mechanism is a coupling identity: in the h-funnel the neutralino–neutralino–Higgs coupling controls both resonant annihilation and the spin-independent cross section $\sigma_{\rm SI}$, and in the Z-funnel the axial-vector neutralino–neutralino–$Z$ coupling controls both resonant annihilation and the spin-dependent cross section $\sigma_{\rm SD}$. Because the finite mediator width and thermal smearing cap the resonant annihilation rate, matching $\Omega h^2 \simeq 0.12$ pins the couplings, and hence the scattering cross sections, above finite lower envelopes. Even after applying the most adverse hadronic shifts (downward rescaling by 22% for $\sigma_{\rm SI}$ and 38% for $\sigma_{\rm SD}$), the predicted rates lie nearly an order of magnitude above the LZ-2024 limit curves, and a background-free Poisson recast calibrated to the official 90% C.L. limit yields exclusion significances above $5.9\sigma$ (h-funnel) and $4.1\sigma$ (Z-funnel), with p-values of $1.8\times10^{-9}$ and $2.1\times10^{-5}$.
Load-bearing premise
The result rests on assuming that a background-free Poisson likelihood calibrated to the published 90% C.L. limit remains a conservative description of the LZ-2024 experiment when extrapolated to the $5.9\sigma$ and $4.1\sigma$ tails, an extrapolation the authors themselves label 'a conservative estimate rather than an official experimental significance.'
Editorial extensions
If this is right
- The h- and Z-funnel regions that survived LZ-2022 are closed by LZ-2024, so a thermal Bino-like neutralino below 100 GeV in the MSSM with heavy sfermions must turn to coannihilation, heavy-Higgs resonance, or a well-tempered Bino–Higgsino mixture.
- The surviving non-coannihilation options favor a neutralino mass scale $\gtrsim 200$ GeV, apart from exceptional configurations such as the weakly constrained stau-coannihilation strip.
- The exclusion is independent of the relic fraction: scaling the event rate by $\Omega h^2/0.12$ when the neutralino is only part of the dark matter does not bring the funnel regions back into agreement with LZ-2024.
- The argument extends to any Majorana dark matter candidate whose relic abundance and nucleon scattering originate from the same $h$- or $Z$-mediated interaction, provided the scattering amplitude is not accidentally suppressed and no additional annihilation or entropy-injection channels intervene.
Reading between the lines
- Editorial inference: because the lower envelopes are irreducible consequences of the relic-density requirement, future direct-detection exposures can only sharpen this exclusion; no experiment weaker than LZ-2024 can reopen the funnel windows.
- Editorial inference: the paper's own comparison shows its Poisson recast gives smaller significances than a dedicated binned-likelihood recast of the same data, so an official LZ-2024 likelihood analysis would plausibly strengthen rather than weaken the quoted significances — a prediction that can be checked when full public information is released.
- Editorial inference: the coupling-identity argument is not MSSM-specific, so simplified dark matter models with $h$ or $Z$ mediators face the same tension; the concrete test is whether such models can hide in coannihilation or heavy-mediator corners.
- Editorial inference: the hadronic-uncertainty direction is one-sided in the h-funnel — the Roy–Steiner value of the pion–nucleon sigma term ($\sigma_{\pi N} \simeq 58$–$59$ MeV) would raise the predicted spin-independent rates, so a future shift toward that value would strengthen the exclusion rather than weaken it.
Original abstract
In the Minimal Supersymmetric Standard Model with heavy sfermions, a sub-hundred-GeV Bino-like neutralino can thermally achieve the observed dark matter abundance only through $h$- or $Z$-resonant annihilation. Since the couplings governing these resonances simultaneously determine the spin-independent and spin-dependent scattering off nucleons, reproducing the relic density imposes irreducible lower envelopes on the scattering cross sections. We evaluate these bounds including the complete one-loop corrections to these vertices, which enhance the direct-detection rates by up to $50\%$ and $30\%$, respectively, adopt the FLAG-2024 nucleon matrix elements with their most adverse $3\sigma$ shifts, and confront the predictions with a likelihood-based recast of the LZ data. We find that the LZ-2024 results exclude both resonant scenarios at conservative one-sided significances exceeding $5.9\sigma$ and $4.1\sigma$, respectively, irrespective of whether the neutralino constitutes all or only part of the dark matter, and independently of LHC electroweakino searches.
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
In the Minimal Supersymmetric Standard Model with heavy sfermions, a sub-hundred-GeV Bino-like neutralino can thermally achieve the observed dark matter abundance only through $h$- or $Z$-resonant annihilation. Since the couplings governing these resonances simultaneously determine the spin-independent and spin-dependent scattering off nucleons, reproducing the relic density imposes irreducible lower envelopes on the scattering cross sections. We evaluate these bounds including the complete one-loop corrections to these vertices, which enhance the direct-detection rates by up to $50\%$ and $30\%$, respectively, adopt the FLAG-2024 nucleon matrix elements with their most adverse $3\sigma$ shifts, and confront the predictions with a likelihood-based recast of the LZ data. We find that the LZ-2024 results exclude both resonant scenarios at conservative one-sided significances exceeding $5.9\sigma$ and $4.1\sigma$, respectively, irrespective of whether the neutralino constitutes all or only part of the dark matter, and independently of LHC electroweakino searches.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | In the Minimal Supersymmetric Standard Model with heavy sfermions, a sub-hundred-GeV Bino-like neutralino can thermally achieve the observed dark matter abundance only through $h$- or $Z$-resonant annihilation. | background 1.00 | 0.08 | 0.03 | asserted 0.95 |
| s1 | Since the couplings governing these resonances simultaneously determine the spin-independent and spin-dependent scattering off nucleons, reproducing the relic density imposes irreducible lower envelopes on the scattering cross sections. | background 0.89 | 0.13 | 0.03 | asserted 1.00 |
| s2 | We evaluate these bounds including the complete one-loop corrections to these vertices, which enhance the direct-detection rates by up to $50\%$ and $30\%$, respectively, adopt the FLAG-2024 nucleon matrix elements with their most adverse $3\sigma$ shifts, and confront the predictions with a likelihood-based recast of the LZ data. | method 0.93 | 0.95 | 0.03 | asserted 0.97 |
| s3 | We find that the LZ-2024 results exclude both resonant scenarios at conservative one-sided significances exceeding $5.9\sigma$ and $4.1\sigma$, respectively, irrespective of whether the neutralino constitutes all or only part of the dark matter, and independently of LHC electroweakino searches. | result 1.00 | 0.96 | 0.96 | 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:2610.10219 by the authors.
References
Discussion
Disagree with the review, or know something it missed? Leave a comment, highlight any passage above to comment on it, or challenge this review formally.