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'''Weakly interacting massive particles''' ('''WIMPs''') are hypothetical particles that are one of the proposed candidates for [[dark matter]].
There exists no formal definition of a WIMP, but broadly, it is an [[elementary particle]] which interacts via [[gravity]] and any other force (or forces) which 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<ref>{{cite journal | last = Garrett | first = Katherine | title = Dark matter: A primer | year = 2010 | journal = Advances in Astronomy | volume = 2011 | issue = 968283 | pages = 1–22 | doi = 10.1155/2011/968283| arxiv = 1006.2483 | bibcode = 2011AdAst2011E...8G | doi-access = free }}</ref> 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 (physics)|cross section]] of <math>\langle \sigma v \rangle</math>
Experimental efforts to detect WIMPs include the search for products of WIMP annihilation, including [[gamma ray]]s, [[neutrino]]s and [[cosmic ray]]s in nearby galaxies and galaxy clusters; direct detection experiments designed to measure the collision of WIMPs with [[Atomic nucleus|nuclei]] in the laboratory, as well as attempts to directly produce WIMPs in colliders, such as the [[Large Hadron Collider]] at [[CERN]].
Because [[supersymmetry|supersymmetric]] extensions of the Standard Model of particle physics readily predict a new particle with these properties, this apparent coincidence is known as the "'''WIMP miracle'''", and a stable supersymmetric partner has long been a prime WIMP candidate.<ref>{{cite journal |last1=Jungman |first1=Gerard |last2=Kamionkowski |first2=Marc |last3=Griest |first3=Kim |year=1996 |title=Supersymmetric dark matter |journal=Physics Reports |volume=267 |issue=5–6 |pages=195–373 |s2cid=119067698 |arxiv=hep-ph/9506380 |bibcode=1996PhR...267..195J |doi=10.1016/0370-1573(95)00058-5}}</ref> However, in the early 2010s, results from [[Dark matter#Direct detection|direct-detection]] experiments and the lack of evidence for supersymmetry at the [[Large Hadron Collider]] (LHC) experiment<ref>{{cite news |url=http://news.discovery.com/space/lhc-discovery-maims-supersymmetry-again-130724.htm |title=LHC discovery maims supersymmetry again |website=Discovery News |archive-date=2016-03-13 |access-date=2014-06-05 |archive-url=https://web.archive.org/web/20160313000505/http://news.discovery.com/space/lhc-discovery-maims-supersymmetry-again-130724.htm |url-status=dead }}</ref><ref>{{cite arXiv |last=Craig |first=Nathaniel |year=2013 |title=The State of Supersymmetry after Run I of the LHC |class=hep-ph |eprint=1309.0528}}</ref> have cast doubt on the simplest WIMP hypothesis.<ref>{{cite journal |last1=Fox |first1=Patrick J. |last2=Jung |first2=Gabriel |last3=Sorensen |first3=Peter |last4=Weiner |first4=Neal |year=2014 |title=Dark matter in light of LUX |journal=Physical Review D |volume=89 |issue=10 |page=103526 |arxiv=1401.0216 |bibcode=2014PhRvD..89j3526F |doi=10.1103/PhysRevD.89.103526}}</ref>
== 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.<ref>{{cite book |last1=Klapdor-Kleingrothaus |first1=H. V. |title=Beyond the Desert |publisher=IOP |year=1998 |editor1=Klapdor-Kleingrothaus |editor-first=V. |volume=1997 |page=485 |chapter=Double beta decay and dark matter search – window to new physics now, and in future (GENIUS) |bibcode=1998hep.ex....2007K |editor2=Paes |editor-first2=H. |arxiv=hep-ex/9802007}}</ref> WIMP-like particles are also predicted by [[universal extra dimension]] and [[little Higgs]] theories.
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The main theoretical characteristics of a WIMP are:
* Interactions only through the [[weak nuclear force]] and [[gravity]], or possibly other interactions with [[Cross section (physics)|cross-sections]] no higher than the weak scale;<ref name="Kamionkowski">{{cite journal |arxiv=hep-ph/9710467 |last1=Kamionkowski |first1=Marc |title=WIMP and Axion Dark Matter |journal=High Energy Physics and Cosmology |volume=14 |pages=394 |year=1997|bibcode=1998hepc.conf..394K }}</ref>
* Large mass compared to standard particles (WIMPs with sub-[[Electron volt|GeV]]/''c''<sup>2</sup> 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".<ref>{{cite
== 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.<ref>{{cite journal|last1=de Swart|first1=J. G.|last2=Bertone|first2=G.|last3=van Dongen|first3=J.|title=How dark matter came to matter|journal=Nature Astronomy|date=2017|volume=1|issue=59|pages=0059|doi=10.1038/s41550-017-0059|arxiv = 1703.00013 |bibcode = 2017NatAs...1E..59D |s2cid=119092226}}</ref> 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.<ref>{{
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.<ref name="Kamionkowski" /> 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.<ref name="Griest" /> 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.<ref name="Kamionkowski" /> If this model is correct, the dark matter particle would have the properties of the WIMP.
== Indirect detection ==
{{see also|Indirect detection of dark matter}}
Because WIMPs may only interact through gravitational and weak forces, they would be extremely difficult to detect. However, 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 galaxy|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 Gamma-ray Space Telescope|Fermi]]-LAT gamma ray telescope<ref>{{cite journal |doi=10.1103/PhysRevD.89.042001 |title=Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope |date=2014 |collaboration=The Fermi-LAT Collaboration |journal=Physical Review D |volume=89 |issue=4 |pages=042001 |arxiv=1310.0828 |last1=Ackermann |first1=M. |display-authors=etal |bibcode=2014PhRvD..89d2001A |s2cid=46664722 }}</ref> and the VERITAS ground-based gamma ray observatory.<ref>{{cite journal |last1=Grube |first1=Jeffrey |title=VERITAS Limits on Dark Matter Annihilation from Dwarf Galaxies |pages=689–692 |author2=VERITAS Collaboration |year=2012 |doi=10.1063/1.4772353 |journal=AIP Conference Proceedings|volume=1505 |bibcode=2012AIPC.1505..689G |arxiv = 1210.4961 |s2cid=118510709 }}</ref> 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; however, by 2014, only 37 cosmological neutrinos had been observed,<ref>{{cite journal |doi=10.1103/PhysRevLett.113.101101 |pmid=25238345 |title=Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data |date=2014 |collaboration=IceCube Collaboration
|journal=Physical Review Letters |volume=113 |issue=10 |pages=101101 |arxiv=1405.5303 |bibcode=2014PhRvL.113j1101A |last1=Aartsen |first1=M. G. |s2cid=220469354 |display-authors=etal}}</ref> 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.<ref name="Griest" /> As more and more WIMPs thermalize inside the Sun, they would begin to [[annihilation|annihilate]] with each other, theoretically forming a variety of particles, including high-energy [[neutrino]]s.<ref>{{cite journal |doi=10.1103/PhysRevD.74.115007 |title=Indirect detection of light neutralino dark matter in the next-to-minimal supersymmetric standard model |date=2006 |last1=Ferrer |first1=F. |last2=Krauss |first2=L. M. |last3=Profumo |first3=S. |journal=Physical Review D |volume=74 |issue=11 |pages=115007 |arxiv=hep-ph/0609257 |bibcode=2006PhRvD..74k5007F |s2cid=119351935 }}</ref> 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<ref>{{cite journal |doi=10.1016/0370-2693(86)90349-7|title=Can scalar neutrinos or massive Dirac neutrinos be the missing mass?|journal=Physics Letters B|volume=167|issue=3|pages=295–300|year=1986|last1=Freese|first1=Katherine|bibcode=1986PhLB..167..295F}}</ref> and from within the galactic center.<ref>{{cite journal |doi=10.1142/S0217732305017391 |title=Dark Matter Dynamics and Indirect Detection |date=2005 |last1=Merritt |first1=D. |last2=Bertone |first2=G. |author-link=David Merritt |journal=Modern Physics Letters A |volume=20 |issue=14 |pages=1021–1036 |arxiv=astro-ph/0504422 |bibcode=2005MPLA...20.1021B |s2cid=119405319 }}</ref><ref>{{
== Direct detection ==
{{see also|Direct detection of dark matter}}
''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.
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[[Image:CDMS parameter space 2004.png |thumb|right|upright=1.6|Fig 1. CDMS parameter space excluded as of 2004. DAMA result is located in green area and is disallowed.]]
=== 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 [[Kelvin|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 [[electrical resistance|resistance]]. [[Cryogenic Rare Event Search with Superconducting Thermometers|CRESST]], [[CoGeNT]], and [[EDELWEISS]] run similar setups.
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'''Crystal scintillators''' – Instead of a liquid noble gas, an in principle simpler approach is the use of a scintillating crystal such as NaI(Tl). This approach is taken by [[DAMA/LIBRA]], an experiment that observed an annular modulation of the signal consistent with WIMP detection (see ''{{section link||Recent limits}}''). Several experiments are attempting to replicate those results, including [[ANAIS]], [[Cryogenic_Observatory_for_Signatures_Seen_in_Next-Generation_Underground_Searches|COSINUS]] and [[DM-Ice]], which is codeploying NaI crystals with the [[IceCube Neutrino Observatory|IceCube]] detector at the South Pole. [[Korea Invisible Mass Search|KIMS]] is approaching the same problem using CsI(Tl) as a scintillator.
'''Bubble chambers''' – The [[PICASSO]] (Project In Canada to Search for Supersymmetric Objects) experiment is a direct dark matter search experiment that is located at [[SNOLAB]] in Canada. It uses bubble detectors with [[Freon]] as the active mass. PICASSO is predominantly sensitive to spin-dependent interactions of WIMPs with the fluorine atoms in the Freon. COUPP, a similar experiment using trifluoroiodomethane(CF<sub>3</sub>I), published limits for mass above 20
A bubble detector is a radiation sensitive device that uses small droplets of superheated liquid that are suspended in a gel matrix.<ref>{{
PICASSO reports results (November 2009) for spin-dependent WIMP interactions on <sup>19</sup>F, for masses of 24 Gev new stringent limits have been obtained on the spin-dependent cross section of 13.9 pb (90% CL). The obtained limits restrict recent interpretations of the DAMA/LIBRA annual modulation effect in terms of spin dependent interactions.<ref>{{cite journal |author=PICASSO Collaboration |title=Dark Matter Spin-Dependent Limits for WIMP Interactions on <sup>19</sup>F by PICASSO |journal=Physics Letters B |date=2009 |doi=10.1016/j.physletb.2009.11.019 |bibcode=2009PhLB..682..185A |volume=682 |issue=2 |pages=185–192 |arxiv=0907.0307|s2cid=15163629 }}</ref>
PICO is an expansion of the concept planned in 2015.<ref>{{
'''Other types of detectors''' – [[Time projection chamber]]s (TPCs) filled with low pressure gases are being studied for WIMP detection. The [[Directional Recoil Identification From Tracks]] (DRIFT) collaboration is attempting to utilize the predicted directionality of the WIMP signal. DRIFT uses a [[carbon disulfide]] target, that allows WIMP recoils to travel several millimetres, leaving a track of charged particles. This charged track is drifted to an [[MWPC]] readout plane that allows it to be reconstructed in three dimensions and determine the origin direction. DMTPC is a similar experiment with CF<sub>4</sub> gas.
The DAMIC (DArk Matter In CCDs) and SENSEI (Sub Electron Noise Skipper CCD Experimental Instrument) collaborations employ the use of scientific [[Charge-coupled device|Charge Coupled Devices]] (CCDs) to detect light Dark Matter. The CCDs act as both the detector target and the readout instrumentation. WIMP interactions with the bulk of the CCD can induce the creation of electron-hole pairs, which are then collected and readout by the CCDs. In order to decrease the noise and achieve detection of single electrons, the experiments make use of a type of CCD known as the Skipper CCD, which allows for averaging over repeated measurements of the same collected charge.<ref>{{
=== Recent limits ===
[[File:Direct Detection Constraints.png
There are currently no confirmed detections of dark matter from direct detection experiments, with the strongest exclusion limits coming from the [[Large Underground Xenon experiment|LUX]] and [[Cryogenic Dark Matter Search|SuperCDMS]] experiments, as shown in figure 2.
With 370 kilograms of xenon, LUX is more sensitive than XENON or CDMS.<ref>
{{cite web |url=https://www.science.org/content/article/new-experiment-torpedoes-lightweight-dark-matter-particles |title=New Experiment Torpedoes Lightweight Dark Matter Particles |date=30 October 2013 |access-date=6 May 2014}}
</ref>
{{cite web |url=http://newscenter.lbl.gov/news-releases/2013/10/30/lux-first-results/ |title=First Results from LUX, the World's Most Sensitive Dark Matter Detector |publisher=Berkeley Lab News Center |date=30 October 2013 |access-date=6 May 2014}}
</ref>
Historically, there have been four anomalous sets of data from different direct detection experiments, two of which have now been explained with backgrounds ([[CoGeNT]] and CRESST-II), and two which remain unexplained ([[DAMA/LIBRA]] and [[Cryogenic Dark Matter Search|CDMS-Si]]).<ref>{{cite journal |title=Largest-ever dark-matter experiment poised to test popular theory |url=http://www.nature.com/news/largest-ever-dark-matter-experiment-poised-to-test-popular-theory-1.18772 |journal=Nature |access-date=15 January 2017|doi=10.1038/nature.2015.18772 |year=2015 |last1=Cartlidge |first1=Edwin |s2cid=182831370 |url-access=subscription }}</ref><ref>{{cite journal |last1=Davis |first1=Jonathan H. |date=2015 |title=The Past and Future of Light Dark Matter Direct Detection |journal=International Journal of Modern Physics A |volume=30 |issue=15 |page=1530038 |arxiv=1506.03924 |bibcode=2015IJMPA..3030038D |doi=10.1142/S0217751X15300380 |s2cid=119269304}}</ref> In February 2010, researchers at CDMS announced that they had observed two events that may have been caused by WIMP-nucleus collisions.<ref name="strib">{{cite web |url=http://www.startribune.com/local/79624932.html?page=1&c=y |title=Key to the universe found on the Iron Range? |website=[[Star Tribune]] |access-date=December 18, 2009}}</ref><ref>
{{ |url = http://cdms.berkeley.edu/0912.3592v1.pdf
|title = Results from the Final Exposure of the CDMS II Experiment
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|archive-url = https://web.archive.org/web/20091229234000/http://cdms.berkeley.edu/0912.3592v1.pdf
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{{ |url = http://cdms.berkeley.edu/results_summary.pdf
|title = Latest Results in the Search for Dark Matter
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}}</ref><ref>{{cite journal |author=The CDMS II Collaboration |date=2010 |title=Dark Matter Search Results from the CDMS II Experiment |journal=Science |volume=327 |issue=5973 |pages=1619–1621 |arxiv=0912.3592 |bibcode=2010Sci...327.1619C |doi=10.1126/science.1186112 |pmid=20150446 |s2cid=2517711}}</ref>
[[CoGeNT]], a smaller detector using a single germanium puck, designed to sense WIMPs with smaller masses, reported hundreds of detection events in 56 days.<ref name="NN-2010-02-26">{{cite journal |author=Hand |first=Eric |date=2010-02-26 |title=A CoGeNT result in the hunt for dark matter |url=http://www.nature.com/news/2010/100226/full/news.2010.97.html |journal=Nature |publisher=Nature News |doi=10.1038/news.2010.97|url-access=subscription }}</ref><ref>{{cite journal |title=Results from a Search for Light-Mass Dark Matter with a P-type Point Contact Germanium Detector |author=C. E. Aalseth |collaboration=CoGeNT collaboration |doi=10.1103/PhysRevLett.106.131301 |date=2011 |journal=Physical Review Letters |volume=106 |issue=13 |arxiv=1002.4703 |bibcode=2011PhRvL.106m1301A |pmid=21517370 |page=131301|s2cid=24822628 }}</ref> They observed an annual modulation in the event rate that could indicate light dark matter.<ref name="Dacey2011">{{cite web |last1=Dacey |first1=James |date=June 2011 |title=CoGeNT findings support dark-matter halo theory |url=http://physicsworld.com/cws/article/news/2011/jun/15/cogent-findings-support-dark-matter-halo-theory |access-date=5 May 2015 |publisher=physicsworld}}</ref> However, a dark matter origin for the CoGeNT events has been refuted by more recent analyses, in favour of an explanation in terms of a background from surface events.<ref>{{cite journal |last1=Davis |first1=Jonathan H. |last2=McCabe |first2=Christopher |last3=Boehm |first3=Celine |title=Quantifying the evidence for Dark Matter in CoGeNT data |journal=Journal of Cosmology and Astroparticle Physics |date=2014 |volume=1408 |issue=8 |page=014 |doi=10.1088/1475-7516/2014/08/014 |arxiv = 1405.0495 |bibcode = 2014JCAP...08..014D |s2cid=54532870 }}</ref>
Annual modulation is one of the predicted signatures of a WIMP signal,<ref>{{cite journal|last1=Drukier|first1=Andrzej K.|last2=Freese|first2=Katherine|last3=Spergel|first3=David N.|title=Detecting cold dark-matter candidates|journal=Physical Review D|date=15 June 1986|volume=33|issue=12|pages=3495–3508|doi=10.1103/PhysRevD.33.3495|pmid=9956575|bibcode=1986PhRvD..33.3495D}}</ref><ref name="Freese1988">{{cite journal |author=Freese |first1=K. |last2=Frieman |first2=J. |last3=Gould |first3=A. |year=1988 |title=Signal Modulation in Cold Dark Matter Detection |journal=Physical Review D |volume=37 |issue=12 |pages=3388–3405 |bibcode=1988PhRvD..37.3388F |doi=10.1103/PhysRevD.37.3388 |osti=1448427 |pmid=9958634 |s2cid=2610174}}</ref> and on this basis the DAMA collaboration has claimed a positive detection. Other groups, however, have not confirmed this result. The CDMS data, made public in May 2004. exclude the entire DAMA signal region given certain standard assumptions about the properties of the WIMPs and the dark matter halo, and this has been followed by many other experiments (see Figure 2).
The [[Korea Invisible Mass Search#COSINE|COSINE-100]] collaboration (a merging of KIMS and DM-Ice groups) published their results on replicating the DAMA/LIBRA signal in December 2018 in journal Nature; their conclusion was that "this result rules out WIMP–nucleon interactions as the cause of the annual modulation observed by the DAMA collaboration".<ref>{{
===
[[File:WIMPsLZexperiment2023.png
The 2020s should see the emergence of several multi-tonne mass direct detection experiments, which will probe WIMP-nucleus cross sections orders of magnitude smaller than the current state-of-the-art sensitivity. Examples of such next-generation experiments are LUX-ZEPLIN (LZ) and XENONnT, which are multi-tonne liquid xenon experiments, followed by DARWIN, another proposed liquid xenon direct detection experiment of 50–100 tonnes.<ref>{{cite arXiv |eprint=1110.0103|last1= Malling|first1= D. C.|title= After LUX: The LZ Program |display-authors= etal |class= astro-ph.IM|year= 2011}}</ref><ref>{{cite journal |last1=Baudis |first1=Laura |title=DARWIN: dark matter WIMP search with noble liquids |journal=J. Phys. Conf. Ser. |date=2012 |volume=375 |issue=1 |page=012028 |doi=10.1088/1742-6596/375/1/012028 |arxiv=1201.2402|bibcode=2012JPhCS.375a2028B |s2cid=30885844 }}</ref>
Such multi-tonne experiments will also face a new background in the form of neutrinos, which will limit their ability to probe the WIMP parameter space beyond a certain point, known as the neutrino floor. However, although its name may imply a hard limit, the neutrino floor represents the region of parameter space beyond which experimental sensitivity can only improve at best as the square root of exposure (the product of detector mass and running time).<ref>{{cite journal |last1=Billard |first1=J. |last2=Strigari |first2=L. |last3=Figueroa-Feliciano |first3=E. |date=2014 |title=Implication of neutrino backgrounds on the reach of next generation dark matter direct detection experiments |journal=Physical Review D |volume=89 |issue=2 |page=023524 |arxiv=1307.5458 |bibcode=2014PhRvD..89b3524B |doi=10.1103/PhysRevD.89.023524 |s2cid=16208132}}</ref><ref>{{cite journal |last1=Davis |first1=Jonathan H. |title=Dark Matter vs. Neutrinos: The effect of astrophysical uncertainties and timing information on the neutrino floor |journal=Journal of Cosmology and Astroparticle Physics |date=2015 |volume=1503 |issue=3 |page=012 |doi=10.1088/1475-7516/2015/03/012 |arxiv=1412.1475|bibcode = 2015JCAP...03..012D |s2cid=118596203 }}</ref> For WIMP masses below 10
In December 2021, results from [[PandaX]] have found no signal in their data, with a lowest excluded cross section of {{val|3.8|e=-47|ul=cm2}} at 40
In July 2023, the [[XENON#XENONnT|XENONnT]] and [[LZ experiment]] published the first results of their searches for WIMPs,<ref>{{
== See also ==
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{div col begin|colwidth=20em}}
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; Theoretical candidates
{{div col begin|colwidth=20em}}
* {{annotated link|Lightest supersymmetric particle|abbreviation=LSP}}
* {{annotated link|Majorana fermion}}
* {{annotated link|Neutralino}}
* {{annotated link|Micro black hole#Conjectures for the final state|Planck-mass-sized black hole remnant}}
* {{annotated link|Sterile neutrino}}
{{div col end}}
<!-- please keep entries in alphabetical order -->
== References ==
{{reflist}}
== Further reading ==
* {{
|last=Bertone
|first=Gianfranco
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|bibcode=2010pdmo.book.....B
}}
* {{
* {{cite journal |last1=Davis |first1=Jonathan H. |title=The Past and Future of Light Dark Matter Direct Detection |journal=International Journal of Modern Physics A |date=2015 |volume=30 |issue=15 |page=1530038 |doi=10.1142/S0217751X15300380 |arxiv=1506.03924 |bibcode=2015IJMPA..3030038D |s2cid=119269304}}
* {{cite journal |title=Update on the Halo-independent Comparison of Direct Dark Matter Detection Data |year=2015 |journal=Physics Procedia |doi=10.1016/j.phpro.2014.12.009 |volume=61 |pages=45–54 |last1=Del Nobile |first1=Eugenio |last2=Gelmini |first2=Graciela B. |last3=Gondolo |first3=Paolo |last4=Huh |first4=Ji-Haeng |bibcode=2015PhPro..61...45D |arxiv = 1405.5582 }}
== External links ==
* [http://pdg.lbl.gov/2004/listings/s030.pdf Particle Data Group review article on WIMP search] (S. Eidelman et al. (Particle Data Group), Physical Letters B 592, 1 (2004) Appendix : OMITTED FROM SUMMARY TABLE).
* [[Timothy J. Sumner]], [https://web.archive.org/web/20061020063709/http://relativity.livingreviews.org/Articles/lrr-2002-4/index.html Experimental Searches for Dark Matter] in Living Reviews in Relativity, Vol 5, 2002.
* [https://www.newscientist.com/article/mg21929320.700-out-of-the-shadows-picking-up-hints-of-dark-matter.html Portraits of darkness, New Scientist, August 31, 2013. Preview only.]
* {{
{{Dark matter}}
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