Detection of dark matter particles Dark matter

1 detection of dark matter particles

1.1 direct detection
1.2 indirect detection
1.3 collider searches dark matter

detection of dark matter particles

if dark matter made of sub-atomic particles, millions, possibly billions, of such particles must pass through every square centimeter of earth each second. many experiments aim test hypothesis. although wimps popular search candidates, axion dark matter experiment (admx) searches axions. candidate heavy hidden sector particles interact ordinary matter via gravity.

these experiments can divided 2 classes: direct detection experiments, search scattering of dark matter particles off atomic nuclei within detector; , indirect detection, products of dark matter particle annihilations or decays.

direct detection

direct detection experiments aim observe low-energy recoils (typically few kevs) of nuclei induced interactions particles of dark matter, (in theory) passing through earth. after such recoil nucleus emit energy e.g. scintillation light or phonons, detected sensitive apparatus. in order crucial maintain low background, , such experiments operate deep underground reduce interference cosmic rays. examples of underground laboratories house direct detection experiments include stawell mine, soudan mine, snolab underground laboratory @ sudbury, gran sasso national laboratory, canfranc underground laboratory, boulby underground laboratory, deep underground science , engineering laboratory , china jinping underground laboratory.

these experiments use either cryogenic or noble liquid detector technologies. cryogenic detectors operating @ temperatures below 100mk, detect heat produced when particle hits atom in crystal absorber such germanium. noble liquid detectors detect scintillation produced particle collision in liquid xenon or argon. cryogenic detector experiments include: cdms, cresst, edelweiss, eureca. noble liquid experiments include zeplin, xenon, deap, ardm, warp, darkside, pandax, , lux, large underground xenon experiment. both of these techniques focus on ability distinguish background particles (which predominantly scatter off electrons) dark matter particles (that scatter off nuclei). other experiments include simple , picasso.

currently there has been no well-established claim of dark matter detection direct detection experiment, leading instead strong upper limits on mass , interaction cross section nucleons of such dark matter particles. dama/nai , more recent dama/libra experimental collaborations claim have detected annual modulation in rate of events in detectors, claim due dark matter. results expectation earth orbits sun, velocity of detector relative dark matter halo vary small amount. claim far unconfirmed , in contradiction negative results other experiments such lux , supercdms.

a special case of direct detection experiments covers directional sensitivity. search strategy based on motion of solar system around galactic center. low pressure time projection chamber makes possible access information on recoiling tracks , constrain wimp-nucleus kinematics. wimps coming direction in sun travelling (roughly towards cygnus) may separated background, should isotropic. directional dark matter experiments include dmtpc, drift, newage , mimac.

indirect detection

collage of 6 cluster collisions dark matter maps. clusters observed in study of how dark matter in clusters of galaxies behaves when clusters collide.




video potential gamma-ray detection of dark matter annihilation around supermassive black holes. (duration 3:13, see file description.)

indirect detection experiments search products of self-annihilation or decay of dark matter particles in outer space. example, in regions of high dark matter density (e.g. centre of our galaxy) 2 dark matter particles annihilate produce gamma rays or standard model particle-antiparticle pairs. alternatively if dark matter particle unstable, decay standard model (or other) particles. these processes detected indirectly through excess of gamma rays, antiprotons or positrons emanating high density regions in our galaxy or others. major difficulty inherent in such searches there various astrophysical sources can mimic signal expected dark matter, , multiple signals required conclusive discovery.

a few of dark matter particles passing through sun or earth may scatter off atoms , lose energy. dark matter may accumulate @ center of these bodies, increasing chance of collision/annihilation. produce distinctive signal in form of high-energy neutrinos. such signal strong indirect proof of wimp dark matter. high-energy neutrino telescopes such amanda, icecube , antares searching signal. detection ligo in september 2015 of gravitational waves, opens possibility of observing dark matter in new way, particularly if form of primordial black holes.

many experimental searches have been undertaken such emission dark matter annihilation or decay, examples of follow. energetic gamma ray experiment telescope observed more gamma rays in 2008 expected milky way, scientists concluded due incorrect estimation of telescope s sensitivity.

the fermi gamma-ray space telescope searching similar gamma rays. in april 2012, analysis of available data large area telescope instrument produced statistical evidence of 130 gev signal in gamma radiation coming center of milky way. wimp annihilation seen probable explanation.

at higher energies, ground-based gamma-ray telescopes have set limits on annihilation of dark matter in dwarf spheroidal galaxies , in clusters of galaxies.

the pamela experiment (launched 2006) detected excess positrons. dark matter annihilation or pulsars. no excess antiprotons observed.

in 2013 results alpha magnetic spectrometer on international space station indicated excess high-energy cosmic rays due dark matter annihilation.

collider searches dark matter

an alternative approach detection of dark matter particles in nature produce them in laboratory. experiments large hadron collider (lhc) may able detect dark matter particles produced in collisions of lhc proton beams. because dark matter particle should have negligible interactions normal visible matter, may detected indirectly (large amounts of) missing energy , momentum escape detectors, provided other (non-negligible) collision products detected.

constraints on dark matter exist lep experiment using similar principle, probing interaction of dark matter particles electrons rather quarks. important note discovery collider searches need corroborated discoveries in indirect or direct detection sectors, in order prove particle discovered in fact dark matter of our universe.