WIMPs
Weak-scale particles that gravitate, cluster, and decline to be detected. Forty years of experimental searches, no detection, but the framework hasn't been refuted.
Placeholder for a 3D visualisation of Dark Matter Candidates. The interactive scene will land in Phase 3. Roughly 26% of the universe's energy density behaves like cold, non-baryonic, gravitationally clustering matter. Plain ΛCDM asserts that dark matter exists; this family asks what it is. Five candidates dominate the literature: WIMPs, axions, primordial black holes, sterile neutrinos, and self-interacting dark matter. Each has a different theoretical motivation, a different production mechanism in the early universe, and a different experimental signature today. None has produced a confirmed detection after decades of dedicated searches.
In one sentence
Hypothetical particles with masses around the weak scale that interact with ordinary matter via the weak nuclear force and gravity but not light. Their thermal abundance from the early universe naturally matches the observed dark matter density. Direct-detection experiments have been searching for decades and have not seen them.
The claim
WIMPs (Weakly Interacting Massive Particles) are particles with masses roughly between a few GeV and a few TeV, with cross sections characteristic of the weak nuclear force. They carry no electric charge, emit no light, and barely interact with ordinary matter. They cluster gravitationally and behave like cold dark matter on cosmological scales. The simplest supersymmetric model predicts a particle (the neutralino) that fits this profile exactly.
The motivation is the so-called WIMP miracle. If a particle with weak-scale mass and weak-scale coupling existed in thermal equilibrium with the early universe's plasma, it would freeze out as the universe expanded and cooled, leaving a relic abundance today that lands very close to the observed dark matter density, without fine-tuning. This coincidence drove the field for decades.
Three experimental fronts test the framework. Direct detection (XENONnT, LZ, PandaX) looks for nuclear recoils as WIMPs scatter off detector atoms. Indirect detection (Fermi-LAT, AMS-02, IceCube) looks for the products of WIMP-WIMP annihilation in the Galactic center, dwarf galaxies, and the Sun. Collider searches at the LHC look for missing-energy signatures. All three produced null results through 2025, pushing the simplest WIMP models into corners. XENONnT's 2025 result set spin-independent WIMP-nucleon cross-section limits below ~10^-48 cm² for masses 30 to 50 GeV.
The family stance
Dark matter is some form of non-baryonic, gravitationally clustering matter that is not in the Standard Model. Multiple specific candidate particles or objects are seriously researched. The case for 'something' beyond ordinary matter is overwhelming; the case for any one specific candidate is not.
Predictions
- Nuclear recoils with characteristic energy spectrum in xenon or argon detectors at rates set by WIMP-nucleon cross-section, WIMP mass, and local halo density
- Gamma rays, antimatter, and neutrinos from WIMP-WIMP annihilation in the Galactic center, dwarf spheroidals, and the Sun
- Missing transverse momentum in LHC events with one or more visible particles (mono-jet, mono-photon, mono-Z)
- Thermal freeze-out yielding Ωh² ≈ 0.12 for ⟨σv⟩ ≈ 3×10^-26 cm³/s, the 'WIMP miracle' relic abundance
Evidence
- XENONnT 2025 set the most stringent spin-independent WIMP-nucleon cross-section limits to date, ~10^-48 cm² at WIMP mass 30 to 50 GeV, with no detection
- Galaxy rotation curves, CMB, gravitational lensing, and cluster collisions all require a CDM-like component, which WIMPs naturally provide
- The thermal-relic calculation lands at the observed dark matter density without fine-tuning, motivating continued searches even after null results
- LZ and DARWIN follow-up programs will reach the 'neutrino fog' where atmospheric neutrinos provide an irreducible background, completing the canonical WIMP search
Counterpoints
- LHC has produced no evidence of weak-scale supersymmetric WIMPs (neutralinos); natural SUSY models with TeV-scale masses now require fine-tuning
- Direct-detection limits exclude the simplest weak-cross-section WIMPs for masses where the WIMP miracle was strongest
- The WIMP miracle is less compelling post-LHC: many of the natural models that gave the coincidence are now constrained or ruled out
- Critics argue WIMPs are becoming unfalsifiable: every null result is met with a more elaborate model variant
Variants in this family
▸Go deeperTechnical detail with proper terminology
The WIMP miracle in numbers: thermal freeze-out gives Ωh² ≈ 3×10^-27 cm³/s / ⟨σv⟩. The observed Ωh² ≈ 0.12 requires ⟨σv⟩ ≈ 3×10^-26 cm³/s, almost exactly the weak-interaction cross section for a particle near the TeV scale.
Direct detection rate: nuclear recoil rate ∝ ρ_DM × σ_χN × A² × v_DM / m_χ, where A is the nuclear mass number. Heavy targets like xenon (A = 131) enhance the spin-independent cross section by A². Coherent neutrino scattering off the target nucleus becomes an irreducible background below σ_χN ~ 10^-49 cm².
Indirect-detection final states: γγ, e+e-, μ+μ-, τ+τ-, bb, tt, WW, ZZ. Each gets a different telescope test. Several 'potential excesses' (Galactic Center GeV gamma-ray excess, 130 GeV line at Fermi-LAT, AMS-02 positron excess) have been published but all admit astrophysical explanations.
Collider missing-mass searches: ATLAS and CMS look for mono-jet, mono-photon, mono-Z events. Simplified DM models in the WIMP regime are excluded below ~1 TeV for typical mediator couplings. No anomaly has emerged at LHC Run 2 or Run 3.
References
- EstablishedLee & Weinberg (1977). Cosmological Lower Bound on Heavy Neutrino Masses. Phys. Rev. Lett. 39, 165
- EstablishedJungman, Kamionkowski & Griest (1996). Supersymmetric dark matter. Phys. Rept. 267, 195
- EstablishedBertone, Hooper & Silk (2005). Particle dark matter: evidence, candidates and constraints. Phys. Rept. 405, 279
- EstablishedSchumann (2019). Direct Detection of WIMP Dark Matter. J. Phys. G 46, 103003
- EstablishedXENON Collaboration (2025). WIMP Dark Matter Search Using a 3.1 Tonne-Year Exposure of the XENONnT Experiment. Phys. Rev. Lett. 135
Last reviewed May 17, 2026
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