Editing Dark matter (section)

=== Direct detection ===
{{Further|Weakly interacting massive particle#Direct detection}}
{{Main|Direct detection of dark matter}}
Direct detection experiments aim to observe low-energy recoils of nuclei (typically a few [[keV]]) induced by interactions with particles of dark matter, which (in theory) are passing through the Earth. After such a recoil, the nucleus will emit energy in the form of [[scintillation (physics)|scintillation]] light or [[phonon]]s as they pass through sensitive detection apparatus. To do so effectively, it is crucial to maintain an extremely low background, which is the reason why such experiments typically operate deep underground, where interference from [[cosmic ray]]s is minimized. Examples of underground laboratories with direct detection experiments include the [[Stawell Underground Physics Laboratory|Stawell mine]], the [[Soudan mine]], the [[SNOLAB]] underground laboratory at [[Greater Sudbury|Sudbury]], the [[Gran Sasso National Laboratory]], the [[Canfranc Underground Laboratory]], the [[Boulby Underground Laboratory]], the [[Deep Underground Science and Engineering Laboratory]] and the [[China Jinping Underground Laboratory]].

These experiments mostly use either cryogenic or noble liquid detector technologies. Cryogenic detectors operating at temperatures below 100&nbsp;mK, detect the heat produced when a particle hits an atom in a crystal absorber such as [[germanium]]. [[Noble gas|Noble liquid]] detectors detect [[scintillation (physics)|scintillation]] produced by a particle collision in liquid [[xenon]] or [[argon]]. Cryogenic detector experiments include such projects as [[Cryogenic Dark Matter Search|CDMS]], [[Cryogenic Rare Event Search with Superconducting Thermometers|CRESST]], [[EDELWEISS]], and [[European Underground Rare Event Calorimeter Array|EURECA]], while noble liquid experiments include [[LZ experiment|LZ]], [[XENON]], [[DEAP]], [[ArDM]], [[WIMP Argon Programme|WARP]], [[DarkSide (dark matter experiment)|DarkSide]], [[PandaX]], and LUX, the [[Large Underground Xenon experiment]]. Both of these techniques focus strongly on their ability to distinguish background particles (which predominantly scatter off electrons) from dark matter particles (that scatter off nuclei). Other experiments include [[SIMPLE (dark matter)|SIMPLE]] and [[PICASSO (dark matter)|PICASSO]], which use alternative methods in their attempts to detect dark matter.

Currently there has been no well-established claim of dark matter detection from a direct detection experiment, leading instead to strong upper limits on the mass and interaction cross section with nucleons of such dark matter particles.<ref>{{cite journal |last1=Drees |first1=M. |last2=Gerbier |first2=G. |title=Dark Matter |journal=Chin. Phys. C |date=2015 |volume=38 |page=090001 |url=http://pdg.lbl.gov/2015/reviews/rpp2015-rev-dark-matter.pdf |archive-url=https://web.archive.org/web/20160722093442/http://pdg.lbl.gov/2015/reviews/rpp2015-rev-dark-matter.pdf |archive-date=2016-07-22 |url-status=live}}</ref> The [[DAMA/NaI]] and more recent [[DAMA/LIBRA]] experimental collaborations have detected an annual modulation in the rate of events in their detectors,<ref>{{cite journal |last1=Bernabei |first1=R. |last2=Belli |first2=P. |last3=Cappella |first3=F. |last4=Cerulli |first4=R. |last5=Dai |first5=C. J. |last6=d'Angelo |first6=A. |last7=He |first7=H. L. |last8=Incicchitti |first8=A. |last9=Kuang |first9=H. H. |last10=Ma |first10=J. M. |last11=Montecchia |first11=F. |last12=Nozzoli |first12=F. |last13=Prosperi |first13=D. |last14=Sheng |first14=X. D. |last15=Ye |first15=Z. P. |display-authors=6 |year=2008 |title=First results from DAMA/LIBRA and the combined results with DAMA/NaI |journal=Eur. Phys. J. C |volume=56 |issue=3 |pages=333–355 |arxiv=0804.2741 |bibcode=2008EPJC...56..333B |doi=10.1140/epjc/s10052-008-0662-y |s2cid=14354488}}</ref><ref>{{cite journal |doi=10.1103/PhysRevD.33.3495 |pmid=9956575 |author1=Drukier, A. |author2=Freese, K. |author3=Spergel, D. |title=Detecting Cold Dark Matter Candidates |journal=Physical Review D |volume=33 |issue=12 |pages=3495–3508 |date=1986 |bibcode=1986PhRvD..33.3495D}}</ref> which they claim is due to dark matter. This results from the expectation that as the Earth orbits the Sun, the velocity of the detector relative to the [[dark matter halo]] will vary by a small amount. This claim is so far unconfirmed and in contradiction with negative results from other experiments such as LUX, SuperCDMS<ref>{{cite journal |last1=Davis |first1=Jonathan H. |title=The past and future of light dark matter direct detection |journal=Int. J. Mod. Phys. A |year=2015 |volume=30 |issue=15 |page=1530038 |doi=10.1142/S0217751X15300380 |arxiv=1506.03924 |bibcode=2015IJMPA..3030038D |s2cid=119269304 }}</ref> and XENON100.<ref>{{cite journal |last1=Aprile |first1=E. |title=Search for electronic recoil event rate modulation with 4&nbsp;years of XENON100 data |journal=Phys. Rev. Lett. |year=2017 |volume=118 |issue=10 |page=101101 |doi=10.1103/PhysRevLett.118.101101 |pmid=28339273 |arxiv=1701.00769|bibcode=2017PhRvL.118j1101A |s2cid=206287497 }}</ref>

A special case of direct detection experiments covers those with directional sensitivity. This is a search strategy based on the motion of the Solar System around the [[Galactic Center]].<ref name="apssyn">{{cite news |last=Stonebraker |first=Alan |title=Synopsis: Dark-Matter Wind Sways through the Seasons |newspaper=Physics – Synopses |publisher=[[American Physical Society]] |date=3 January 2014 |doi=10.1103/PhysRevLett.112.011301 }}</ref><ref name="samlee">{{cite journal |last1=Lee |first1=Samuel K. |first2=Mariangela |last2=Lisanti |first3=Annika H.G.|last3=Peter |first4=Benjamin R.|last4=Safdi |doi=10.1103/PhysRevLett.112.011301 |arxiv=1308.1953 |title=Effect of Gravitational Focusing on Annual Modulation in Dark-Matter Direct-Detection Experiments |date=3 January 2014 |journal=Phys. Rev. Lett. |volume=112 |issue=1 |page=011301 [5 pages] |bibcode=2014PhRvL.112a1301L |pmid=24483881|s2cid=34109648 }}</ref><ref name="dmgsheff">{{cite news |last=The Dark Matter Group |title=An Introduction to Dark Matter |newspaper=Dark Matter Research |location=Sheffield |publisher=University of Sheffield |url=http://www.hep.shef.ac.uk/research/dm/intro.php |access-date=7 January 2014 |archive-date=29 July 2020 |archive-url=https://web.archive.org/web/20200729020742/http://www.hep.shef.ac.uk/research/dm/intro.php  }}</ref><ref name="Kavli">{{cite news |quote=Scientists at Kavli MIT are working on ... a tool to track the movement of dark matter. |title=Blowing in the Wind |newspaper=Kavli News |location=Sheffield |publisher=[[Kavli Foundation (United States)|Kavli Foundation]] |url=http://www.kavlifoundation.org/science-spotlights/blowing-wind |access-date=7 January 2014 |archive-date=7 October 2020 |archive-url=https://web.archive.org/web/20201007192326/http://www.kavlifoundation.org/science-spotlights/blowing-wind |url-status=dead }}</ref> A low-pressure [[time projection chamber]] makes it possible to access information on recoiling tracks and constrain WIMP-nucleus kinematics. WIMPs coming from the direction in which the Sun travels (approximately towards [[Cygnus (constellation)|Cygnus]]) may then be separated from background, which should be isotropic. Directional dark matter experiments include [[Dark Matter Time Projection Chamber|DMTPC]], [[Directional Recoil Identification From Tracks|DRIFT]], Newage and MIMAC.