Weakly interacting massive particle: Difference between revisions

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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 ==

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* Large mass compared to standard particles (WIMPs with sub-[[Electron volt|GeV]]/''c''² 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 journalbook |arxiv=0707.0472 |last1=Zacek |first1=Viktor |title=Fundamental Interactions |chapter=Dark Matter |year=2007 |doi=10.1142/9789812776105_0007 |journal=Fundamental Interactions|pages=170–206 |isbn=978-981-277-609-9 |s2cid=16734425 }}</ref> Their relatively low velocities would be insufficient to overcome the mutual gravitational attraction, and as a result, WIMPs would tend to clump together.<ref name="Griest">{{cite journal |arxiv=hep-ph/9303253 |last1=Griest |first1=Kim |title=The Search for the Dark Matter: WIMPs and MACHOs |journal=Annals of the New York Academy of Sciences |volume=688 |pages=390–407 |year=1993 |doi=10.1111/j.1749-6632.1993.tb43912.x|pmid=26469437 |bibcode=1993NYASA.688..390G |s2cid=8955141 }}</ref> 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.<ref>{{cite journal |doi=10.1086/169575 |last=Griest |first=Kim |title=Galactic Microlensing as a Method of Detecting Massive Compact Halo Objects |journal=The Astrophysical Journal |date=1991 |volume=366 |pages=412–421 |bibcode=1991ApJ...366..412G}}</ref> 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 [[neutrino]]s, are very light, and hence would be fast moving, or "hot".

== As dark matter ==

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=== Recent limits ===

[[File:Direct Detection Constraints.png |frame|Figure 2: Plot showing the parameter space of dark matter particle mass and interaction cross section with nucleons. The LUX and SuperCDMS limits exclude the parameter space above the labelled curves. The CoGeNT and CRESST-II regions indicate regions which were previously thought to correspond to dark matter signals, but which were later explained with mundane sources. The DAMA and CDMS-Si data remain unexplained, and these regions indicate the preferred parameter space if these anomalies are due to dark matter.|thumb|426x426px]]

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.

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=== Future of direct detection ===

[[File:WIMPsLZexperiment2023.png|frame|Upper limits for WIMP-nucleon elastic cross sections from selected experiments as reported by the LZ experiment in July 2023.|thumb|431x431px]]

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>