Weakly interacting massive particles (WIMPs) are hypothetical particles that are one of the proposed candidates for dark matter. These particles would have mass and would interact with gravity, would have been created in abundance during the Big Bang, and would since have reduced in number because of self-annihilation caused by their weak interaction.
There exists no formal definition of a WIMP, but broadly, it is an elementary particle that interacts via gravity and any other force (or forces) that is as weak as or weaker than the weak nuclear force, but also non-vanishing in strength. Many WIMP candidates are expected to have been produced thermally in the early Universe, similarly to the particles of the Standard Model according to Big Bang cosmology, and usually will constitute cold dark matter. Obtaining the correct abundance of dark matter today via thermal production requires a self-annihilation cross section of ≃ , which is roughly what is expected for a new particle in the 100 GeV/c2 mass range that interacts via the electroweak force.
Experimental efforts to detect WIMPs include the search for products of WIMP annihilation, including gamma rays, neutrinos and cosmic rays in nearby galaxies and galaxy clusters; direct detection experiments designed to measure the collision of WIMPs with nuclei in the laboratory, as well as attempts to directly produce WIMPs in colliders, such as the Large Hadron Collider at CERN. As of 2026, none of these efforts have shown success.
Supersymmetric extensions of the Standard Model of particle physics readily predict new particles that could serve as WIMPs. This apparent coincidence is known as the "WIMP miracle", and a stable supersymmetric partner has long been a prime WIMP candidate. These candidate WIMPs include neutralinos and gravitinos. The lack of evidence for supersymmetry at the Large Hadron Collider (LHC) experiment have cast doubt on these simplest WIMP hypotheses, however.
Theoretical framework and properties WIMP-like particles are predicted by R-parity-conserving supersymmetry, a type of extension to the Standard Model of particle physics, although none of the large number of new particles in supersymmetry have been observed. WIMP-like particles are also predicted by universal extra dimension and little Higgs theories. Model parity candidate SUSY R-parity lightest supersymmetric particle (LSP) UED KK-parity lightest Kaluza–Klein particle (LKP) little Higgs T-parity lightest T-odd particle (LTP)
The main theoretical characteristics of a WIMP are: Interactions only through the weak nuclear force and gravity, or possibly other interactions with cross-sections no higher than the weak scale; Large mass compared to standard particles (WIMPs with sub-GeV/c2 masses may be considered to be light dark matter).
Because of their lack of electromagnetic interaction with normal matter, WIMPs would be invisible through normal electromagnetic observations. Because of their large mass, they would be relatively slow moving and therefore "cold". Their relatively low velocities would be insufficient to overcome the mutual gravitational attraction, and as a result, WIMPs would tend to clump together. WIMPs are considered one of the main candidates for cold dark matter, the others being massive compact halo objects (MACHOs) and axions. These names were deliberately chosen for contrast, with MACHOs named later than WIMPs. In contrast to WIMPs, there are no known stable particles within the Standard Model of particle physics that have the properties of MACHOs. The particles that have little interaction with normal matter, such as neutrinos, are very light, and hence would be fast moving, or "hot".
As dark matter
A decade after the dark matter problem was established in the 1970s, WIMPs were suggested as a potential solution to the issue. Although the existence of WIMPs in nature is still hypothetical, it would resolve a number of astrophysical and cosmological problems related to dark matter. There is consensus today among astronomers that most of the mass in the Universe is indeed dark. Simulations of a universe full of cold dark matter produce galaxy distributions that are roughly similar to what is observed.The Millennium Simulation Project, Introduction: The Millennium Simulation The Millennium Run used more than 10 billion particles to trace the evolution of the matter distribution in a cubic region of the Universe over 2 billion light-years on a side. By contrast, hot dark matter would smear out the large-scale structure of galaxies and thus is not considered a viable cosmological model.
WIMPs fit the model of a relic dark matter particle from the early Universe, when all particles were in a state of thermal equilibrium. For sufficiently high temperatures, such as those existing in the early Universe, the dark matter particle and its antiparticle would have been both forming from and annihilating into lighter particles. As the Universe expanded and cooled, the average thermal energy of these lighter particles decreased and eventually became insufficient to form a dark matter particle-antiparticle pair. The annihilation of the dark matter particle-antiparticle pairs, however, would have continued, and the number density of dark matter particles would have begun to decrease exponentially. Eventually, however, the number density would become so low that the dark matter particle and antiparticle interaction would cease, and the number of dark matter particles would remain (roughly) constant as the Universe continued to expand. Particles with a larger interaction cross section would continue to annihilate for a longer period of time, and thus would have a smaller number density when the annihilation interaction ceases. Based on the current estimated abundance of dark matter in the Universe, if the dark matter particle is such a relic particle, the interaction cross section governing the particle-antiparticle annihilation can be no larger than the cross section for the weak interaction. If this model is correct, the dark matter particle would have the properties of the WIMP.
Indirect detection
Because WIMPs may only interact through gravitational and weak forces, they would be extremely difficult to detect. Nonetheless, there are many experiments underway to attempt to detect WIMPs both directly and indirectly. Indirect detection refers to the observation of annihilation or decay products of WIMPs far away from Earth. Indirect detection efforts typically focus on locations where WIMP dark matter is thought to accumulate the most: in the centers of galaxies and galaxy clusters, as well as in the smaller satellite galaxies of the Milky Way. These are particularly useful since they tend to contain very little baryonic matter, reducing the expected background from standard astrophysical processes. Typical indirect searches look for excess gamma rays, which are predicted both as final-state products of annihilation, or are produced as charged particles interact with ambient radiation via inverse Compton scattering. The spectrum and intensity of a gamma ray signal depends on the annihilation products, and must be computed on a model-by-model basis. Experiments that have placed bounds on WIMP annihilation, via the non-observation of an annihilation signal, include the Fermi-LAT gamma ray telescope and the VERITAS ground-based gamma ray observatory. The Galactic Center GeV excess and a similar 21-GeV excess in the Galactic halo have been proposed to be caused by WIMP annihilation. Although the annihilation of WIMPs into Standard Model particles also predicts the production of high-energy neutrinos, their interaction rate is thought to be too low to reliably detect a dark matter signal at present. Future observations from the IceCube observatory in Antarctica may be able to differentiate WIMP-produced neutrinos from standard astrophysical neutrinos; by 2014, only 37 cosmological neutrinos had been observed, making such a distinction impossible.
Another type of indirect WIMP signal could come from the Sun. Halo WIMPs may, as they pass through the Sun, interact with solar protons, helium nuclei as well as heavier elements. If a WIMP loses enough energy in such an interaction to fall below the local escape velocity, it would theoretically not have enough energy to escape the gravitational pull of the Sun and would remain gravitationally bound. As more and more WIMPs thermalize inside the Sun, they would begin to annihilate with each other, theoretically forming a variety of particles, including high-energy neutrinos. These neutrinos may then travel to the Earth to be detected in one of the many neutrino telescopes, such as the Super-Kamiokande detector in Japan. The number of neutrino events detected per day at these detectors depends on the properties of the WIMP, as well as on the mass of the Higgs boson. Similar experiments are underway to attempt to detect neutrinos from WIMP annihilations within the Earth and from within the galactic center.
Direct detection
Direct detection refers to the observation of the effects of a WIMP-nucleus collision as the dark matter passes through a detector in an Earth laboratory. While most WIMP models indicate that a large enough number of WIMPs must be captured in large celestial bodies for indirect detection experiments to succeed, it remains possible that these models are either incorrect or only explain part of the dark matter phenomenon. Thus, even with the multiple experiments dedicated to providing indirect evidence for the existence of cold dark matter, direct detection measurements are also necessary to solidify the theory of WIMPs.
Although most WIMPs encountering the Sun or the Earth are expected to pass through without any effect, it is hoped that a large number of dark matter WIMPs crossing a sufficiently large detector will interact often enough to be seen—at least a few events per year. The general strategy of current attempts to detect WIMPs is to find very sensitive systems that can be scaled to large volumes. This follows the lessons learned from the history of the discovery, and (by now routine) detection, of the neutrino.
Experimental techniques
Cryogenic crystal detectors – A technique used by the Cryogenic Dark Matter Search (CDMS) detector at the Soudan Mine relies on multiple very cold germanium and silicon crystals. The crystals (each about the size of a hockey puck) are cooled to about 50 mK. A layer of metal (aluminium and tungsten) at the surfaces is used to detect a WIMP passing through the crystal. This design hopes to detect vibrations in the crystal matrix generated by an atom being "kicked" by a WIMP. The tungsten transition edge sensors (TES) are held at the critical temperature so they are in the superconducting state. Large crystal vibrations will generate heat in the metal and are detectable because of a change in resistance. CRESST, CoGeNT, and EDELWEISS run similar setups.
Noble gas scintillators – Another way of detecting atoms "knocked about" by a WIMP is to use scintillating material, so that light pulses are generated by the moving atom and detected, often with PMTs. Experiments such as DEAP at SNOLAB and DarkSide at the LNGS instrument a very large target mass of liquid argon for sensitive WIMP searches. ZEPLIN, and XENON used xenon to exclude WIMPs at higher sensitivity, with the most stringent limits to date provided by the XENON1T detector, utilizing 3.5 tons of liquid xenon. Even larger multi-ton liquid xenon detectors have been approved for construction from the XENON, LUX-ZEPLIN and PandaX collaborations.