Misplaced Pages

#923076

83-535: 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 according to Big Bang cosmology, and usually will constitute cold dark matter . Obtaining

166-485: A jet of particles is emitted. This inelastic scattering suggests that the charge in the proton is not uniform but split among smaller charged particles: quarks. In the Standard Model, vector ( spin -1) bosons ( gluons , photons , and the W and Z bosons ) mediate forces, whereas the Higgs boson (spin-0) is responsible for the intrinsic mass of particles. Bosons differ from fermions in the fact that multiple bosons can occupy

249-428: A WIMP are: 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

332-636: A color-neutral baryon . Symmetrically, three antiquarks with the colors "antired", "antiblue" and "antigreen" can form a color-neutral antibaryon . Quarks also carry fractional electric charges , but, since they are confined within hadrons whose charges are all integral, fractional charges have never been isolated. Note that quarks have electric charges of either ⁠+ + 2 / 3 ⁠   e or ⁠− + 1 / 3 ⁠   e , whereas antiquarks have corresponding electric charges of either ⁠− + 2 / 3 ⁠   e or  ⁠+ + 1 / 3 ⁠   e . Evidence for

415-452: A consequence of flavor and color combinations and antimatter , the fermions and bosons are known to have 48 and 13 variations, respectively. Among the 61 elementary particles embraced by the Standard Model number: electrons and other leptons , quarks , and the fundamental bosons . Subatomic particles such as protons or neutrons , which contain two or more elementary particles, are known as composite particles . Ordinary matter

498-520: 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

581-420: A fact explained by confinement . Every quark carries one of three color charges of the strong interaction ; antiquarks similarly carry anticolor. Color-charged particles interact via gluon exchange in the same way that charged particles interact via photon exchange. Gluons are themselves color-charged, however, resulting in an amplification of the strong force as color-charged particles are separated. Unlike

664-602: 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. 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

747-419: 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 § Recent limits ). Several experiments are attempting to replicate those results, including ANAIS , COSINUS and DM-Ice , which is codeploying NaI crystals with

830-440: A loop (a one-dimensional sphere, that is, a circle). As a string moves through space it sweeps out something called a world sheet . String theory predicts 1- to 10-branes (a 1- brane being a string and a 10-brane being a 10-dimensional object) that prevent tears in the "fabric" of space using the uncertainty principle (e.g., the electron orbiting a hydrogen atom has the probability, albeit small, that it could be anywhere else in

913-423: A neutron into a proton then decays into an electron and electron-antineutrino pair. The Z does not convert particle flavor or charges, but rather changes momentum; it is the only mechanism for elastically scattering neutrinos. The weak gauge bosons were discovered due to momentum change in electrons from neutrino-Z exchange. The massless photon mediates the electromagnetic interaction . These four gauge bosons form

SECTION 10

#1733094264924

996-490: 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). For WIMP masses below 10 GeV

1079-512: A new theory of so-called Techniquarks, interacting via so called Technigluons. The main idea is that the Higgs boson is not an elementary particle but a bound state of these objects. According to preon theory there are one or more orders of particles more fundamental than those (or most of those) found in the Standard Model. The most fundamental of these are normally called preons, which is derived from "pre-quarks". In essence, preon theory tries to do for

1162-620: A similar annual modulation suggesting the signal could be just a statistical artifact supporting a hypothesis first put forward in 2020. 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. Such multi-tonne experiments will also face

1245-472: A smaller detector using a single germanium puck, designed to sense WIMPs with smaller masses, reported hundreds of detection events in 56 days. They observed an annual modulation in the event rate that could indicate light dark matter. 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. Annual modulation

1328-642: A type of CCD known as the Skipper CCD, which allows for averaging over repeated measurements of the same collected charge. There are currently no confirmed detections of dark matter from direct detection experiments, with the strongest exclusion limits coming from the LUX and SuperCDMS experiments, as shown in figure 2. With 370 kilograms of xenon LUX is more sensitive than XENON or CDMS. First results from October 2013 report that no signals were seen, appearing to refute results obtained from less sensitive instruments. and this

1411-528: 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. Crystal scintillators – Instead of

1494-488: Is a consequence of the high masses of the W and Z bosons, which in turn are a consequence of the Higgs mechanism . Through the process of spontaneous symmetry breaking , the Higgs selects a special direction in electroweak space that causes three electroweak particles to become very heavy (the weak bosons) and one to remain with an undefined rest mass as it is always in motion (the photon). On 4 July 2012, after many years of experimentally searching for evidence of its existence,

1577-524: Is a form of matter that neither emits nor absorbs light. Within physics, this behavior is characterized by dark matter not interacting with electromagnetic radiation , hence making it dark and rendering it undetectable via conventional instruments in physics. Data from galaxy rotation curves indicate that approximately 80% of the mass of a galaxy cannot be seen, forcing researchers to innovate ways that indirectly detect it through dark matter's effects on gravitational fluctuations. As we shall see below, it

1660-527: 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 4 gas. The DAMIC (DArk Matter In CCDs) and SENSEI (Sub Electron Noise Skipper CCD Experimental Instrument) collaborations employ

1743-688: Is composed of atoms , themselves once thought to be indivisible elementary particles. The name atom comes from the Ancient Greek word ἄτομος ( atomos ) which means indivisible or uncuttable . Despite the theories about atoms that had existed for thousands of years the factual existence of atoms remained controversial until 1905. In that year Albert Einstein published his paper on Brownian motion , putting to rest theories that had regarded molecules as mathematical illusions. Einstein subsequently identified matter as ultimately composed of various concentrations of energy . Subatomic constituents of

SECTION 20

#1733094264924

1826-568: Is differentiated via the spin–statistics theorem : it is half-integer for fermions, and integer for bosons. Notes : [†] An anti-electron ( e ) is conventionally called a " positron ". [‡] The known force carrier bosons all have spin = 1. The hypothetical graviton has spin = 2; it is unknown whether it is a gauge boson as well. In the Standard Model , elementary particles are represented for predictive utility as point particles . Though extremely successful,

1909-442: Is massless, although some models containing massive Kaluza–Klein gravitons exist. Although experimental evidence overwhelmingly confirms the predictions derived from the Standard Model , some of its parameters were added arbitrarily, not determined by a particular explanation, which remain mysterious, for instance the hierarchy problem . Theories beyond the Standard Model attempt to resolve these shortcomings. One extension of

1992-407: Is necessary to invoke cold dark matter or WDM. In other words, hot dark matter being the sole substance in explaining cosmic galaxy formation is no longer viable, placing hot dark matter under the larger umbrella of mixed dark matter (MDM) theory. An example of a hot dark matter particle is the neutrino . Neutrinos have very small masses, and do not take part in two of the four fundamental forces,

2075-499: Is observed. 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

2158-673: Is one of the predicted signatures of a WIMP signal, 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 COSINE-100 collaboration (a merging of KIMS and DM-Ice groups) published their results on replicating

2241-399: Is roughly what is expected for a new particle in the 100  GeV 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

2324-520: Is the existence of X and Y bosons , which cause proton decay . The non-observation of proton decay at the Super-Kamiokande neutrino observatory rules out the simplest GUTs, however, including SU(5) and SO(10). Supersymmetry extends the Standard Model by adding another class of symmetries to the Lagrangian . These symmetries exchange fermionic particles with bosonic ones. Such a symmetry predicts

2407-437: Is the level of significance required to officially label experimental observations as a discovery . Research into the properties of the newly discovered particle continues. The graviton is a hypothetical elementary spin-2 particle proposed to mediate gravitation. While it remains undiscovered due to the difficulty inherent in its detection , it is sometimes included in tables of elementary particles. The conventional graviton

2490-550: Is useful to differentiate dark matter into "hot" (HDM) and " cold " (CDM) types–some even suggesting a middle-ground of "warm" dark matter (WDM). The terminology refers to the mass of the dark matter particles (which dictates the speed at which they travel): HDM travels faster than CDM because the HDM particles are theorized to be of lower mass. In terms of its application, the distribution of hot dark matter could also help explain how clusters and superclusters of galaxies formed after

2573-541: The Big Bang . Theorists claim that there exist two classes of dark matter: 1) those that "congregate around individual members of a cluster of visible galaxies" and 2) those that encompass "the clusters as a whole." Because cold dark matter possesses a lower velocity, it could be the source of "smaller, galaxy-sized lumps," as shown in the image. Hot dark matter, then, should correspond to the formation of larger mass aggregates that surround whole galaxy clusters. However, data from

Weakly interacting massive particle - Misplaced Pages Continue

2656-420: The Higgs boson was announced to have been observed at CERN's Large Hadron Collider. Peter Higgs who first posited the existence of the Higgs boson was present at the announcement. The Higgs boson is believed to have a mass of approximately 125 GeV/ c . The statistical significance of this discovery was reported as 5 sigma, which implies a certainty of roughly 99.99994%. In particle physics, this

2739-587: The IceCube detector at the South Pole. 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

2822-519: The Large Hadron Collider ( ATLAS and CMS ). The Standard Model is widely considered to be a provisional theory rather than a truly fundamental one, however, since it is not known if it is compatible with Einstein 's general relativity . There may be hypothetical elementary particles not described by the Standard Model, such as the graviton , the particle that would carry the gravitational force , and sparticles , supersymmetric partners of

2905-516: The Large Hadron Collider at CERN . String theory is a model of physics whereby all "particles" that make up matter are composed of strings (measuring at the Planck length) that exist in an 11-dimensional (according to M-theory , the leading version) or 12-dimensional (according to F-theory ) universe. These strings vibrate at different frequencies that determine mass, electric charge, color charge, and spin. A "string" can be open (a line) or closed in

2988-403: The atomic nucleus . Like quarks, gluons exhibit color and anticolor – unrelated to the concept of visual color and rather the particles' strong interactions – sometimes in combinations, altogether eight variations of gluons. There are three weak gauge bosons : W , W , and Z ; these mediate the weak interaction . The W bosons are known for their mediation in nuclear decay: The W converts

3071-467: The cosmic microwave background radiation, as measured by the COBE satellite, is highly uniform, and such high-velocity hot dark matter particles cannot form clumps as small as galaxies beginning from such a smooth initial state, highlighting a discrepancy in what dark matter theory and the actual data are saying. Theoretically, in order to explain relatively small-scale structures in the observable Universe , it

3154-562: The electromagnetic force , which diminishes as charged particles separate, color-charged particles feel increasing force. Nonetheless, color-charged particles may combine to form color neutral composite particles called hadrons . A quark may pair up with an antiquark: the quark has a color and the antiquark has the corresponding anticolor. The color and anticolor cancel out, forming a color neutral meson . Alternatively, three quarks can exist together, one quark being "red", another "blue", another "green". These three colored quarks together form

3237-409: The on-shell scheme . Estimates of the values of quark masses depend on the version of quantum chromodynamics used to describe quark interactions. Quarks are always confined in an envelope of gluons that confer vastly greater mass to the mesons and baryons where quarks occur, so values for quark masses cannot be measured directly. Since their masses are so small compared to the effective mass of

3320-428: The " multiverse " outside our known universe). Some predictions of the string theory include existence of extremely massive counterparts of ordinary particles due to vibrational excitations of the fundamental string and existence of a massless spin-2 particle behaving like the graviton . Technicolor theories try to modify the Standard Model in a minimal way by introducing a new QCD-like interaction. This means one adds

3403-560: 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". In 2021 new results from COSINE-100 and ANAIS-112 both failed to replicate the DAMA/LIBRA signal and in August 2022 COSINE-100 applied an analysis method similar to one used by DAMA/LIBRA and found

Weakly interacting massive particle - Misplaced Pages Continue

3486-403: The Standard Model attempts to combine the electroweak interaction with the strong interaction into a single 'grand unified theory' (GUT). Such a force would be spontaneously broken into the three forces by a Higgs-like mechanism . This breakdown is theorized to occur at high energies, making it difficult to observe unification in a laboratory. The most dramatic prediction of grand unification

3569-606: The Standard Model have been made since its codification in the 1970s. These include notions of supersymmetry , which double the number of elementary particles by hypothesizing that each known particle associates with a "shadow" partner far more massive. However, like an additional elementary boson mediating gravitation, such superpartners remain undiscovered as of 2024. All elementary particles are either bosons or fermions . These classes are distinguished by their quantum statistics : fermions obey Fermi–Dirac statistics and bosons obey Bose–Einstein statistics . Their spin

3652-416: The Standard Model is limited by its omission of gravitation and has some parameters arbitrarily added but unexplained. According to the current models of Big Bang nucleosynthesis , the primordial composition of visible matter of the universe should be about 75% hydrogen and 25% helium-4 (in mass). Neutrons are made up of one up and two down quarks, while protons are made of two up and one down quark. Since

3735-447: The Standard Model what the Standard Model did for the particle zoo that came before it. Most models assume that almost everything in the Standard Model can be explained in terms of three to six more fundamental particles and the rules that govern their interactions. Interest in preons has waned since the simplest models were experimentally ruled out in the 1980s. Accelerons are the hypothetical subatomic particles that integrally link

3818-504: 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

3901-486: 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

3984-553: 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. 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

4067-450: The atom were first identified toward the end of the 19th century , beginning with the electron , followed by the proton in 1919, the photon in the 1920s, and the neutron in 1932. By that time the advent of quantum mechanics had radically altered the definition of a "particle" by putting forward an understanding in which they carried out a simultaneous existence as matter waves . Many theoretical elaborations upon, and beyond ,

4150-419: The correct abundance of dark matter today via thermal production requires a self- annihilation cross section of ⟨ σ v ⟩ ≃ 3 × 10 − 26 c m 3 s − 1 {\displaystyle \langle \sigma v\rangle \simeq 3\times 10^{-26}\mathrm {cm} ^{3}\;\mathrm {s} ^{-1}} , which

4233-523: The current experimental and theoretical knowledge about elementary particle physics is the Particle Data Group , where different international institutions collect all experimental data and give short reviews over the contemporary theoretical understanding. other pages are: Hot dark matter Hot dark matter ( HDM ) is a theoretical form of dark matter which consists of particles that travel with ultrarelativistic velocities. Dark matter

SECTION 50

#1733094264924

4316-429: 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

4399-474: 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

4482-480: 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

4565-463: The detector is almost insensitive to background radiation. The detector sensitivity can be adjusted by changing the temperature, typically operated between 15 °C and 55 °C. There is another similar experiment using this technique in Europe called SIMPLE. PICASSO reports results (November 2009) for spin-dependent WIMP interactions on F, for masses of 24 Gev new stringent limits have been obtained on

4648-531: The dominant source of neutrino background is from the Sun , while for higher masses the background contains contributions from atmospheric neutrinos and the diffuse supernova neutrino background . In December 2021, results from PandaX have found no signal in their data, with a lowest excluded cross section of 3.8 × 10  cm at 40 GeV with 90% confidence level. In July 2023 the XENONnT and LZ experiment published

4731-578: The early 2010s, results from direct-detection experiments along with the lack of evidence for supersymmetry at the Large Hadron Collider (LHC) experiment has cast doubt on the simplest WIMP hypothesis. 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. The main theoretical characteristics of

4814-468: The electroweak interaction among elementary particles. Although the weak and electromagnetic forces appear quite different to us at everyday energies, the two forces are theorized to unify as a single electroweak force at high energies. This prediction was clearly confirmed by measurements of cross-sections for high-energy electron-proton scattering at the HERA collider at DESY . The differences at low energies

4897-543: The existence of supersymmetric particles , abbreviated as sparticles , which include the sleptons , squarks , neutralinos , and charginos . Each particle in the Standard Model would have a superpartner whose spin differs by 1 ⁄ 2 from the ordinary particle. Due to the breaking of supersymmetry , the sparticles are much heavier than their ordinary counterparts; they are so heavy that existing particle colliders would not be powerful enough to produce them. Some physicists believe that sparticles will be detected by

4980-483: The existence of quarks comes from deep inelastic scattering : firing electrons at nuclei to determine the distribution of charge within nucleons (which are baryons). If the charge is uniform, the electric field around the proton should be uniform and the electron should scatter elastically. Low-energy electrons do scatter in this way, but, above a particular energy, the protons deflect some electrons through large angles. The recoiling electron has much less energy and

5063-484: 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

SECTION 60

#1733094264924

5146-530: The first results of their searches for WIMPs, the first excluding cross sections above 2.58 × 10 cm at 28 GeV with 90% confidence level and the second excluding cross sections above 9.2 × 10 cm at 36 GeV with 90% confidence level. Elementary particle In particle physics , an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. The Standard Model presently recognizes seventeen distinct particles—twelve fermions and five bosons . As

5229-449: The fluorine atoms in the Freon. COUPP, a similar experiment using trifluoroiodomethane(CF 3 I), published limits for mass above 20 GeV in 2011. The two experiments merged into PICO collaboration in 2012. A bubble detector is a radiation sensitive device that uses small droplets of superheated liquid that are suspended in a gel matrix. It uses the principle of a bubble chamber but, since only

5312-402: The laboratory, as well as attempts to directly produce WIMPs in colliders, such as the Large Hadron Collider at CERN . Because 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. However, in

5395-502: 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". A decade after

5478-572: 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 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

5561-454: 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

5644-452: The newfound mass of the neutrino to the dark energy conjectured to be accelerating the expansion of the universe . In this theory, neutrinos are influenced by a new force resulting from their interactions with accelerons, leading to dark energy. Dark energy results as the universe tries to pull neutrinos apart. Accelerons are thought to interact with matter more infrequently than they do with neutrinos. The most important address about

5727-749: The non-observation of an annihilation signal, include the Fermi -LAT gamma ray telescope and the VERITAS ground-based gamma ray observatory. 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, making such

5810-477: The observable universe. The number of protons in the observable universe is called the Eddington number . In terms of number of particles, some estimates imply that nearly all the matter, excluding dark matter , occurs in neutrinos, which constitute the majority of the roughly 10 elementary particles of matter that exist in the visible universe. Other estimates imply that roughly 10 elementary particles exist in

5893-453: 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

5976-466: The only elementary fermions with neither electric nor color charge . The remaining six particles are quarks (discussed below). The following table lists current measured masses and mass estimates for all the fermions, using the same scale of measure: millions of electron-volts relative to square of light speed (MeV/ c ). For example, the most accurately known quark mass is of the top quark ( t ) at 172.7  GeV/ c , estimated using

6059-475: The ordinary particles. The 12 fundamental fermions are divided into 3  generations of 4 particles each. Half of the fermions are leptons , three of which have an electric charge of −1  e , called the electron ( e ), the muon ( μ ), and the tau ( τ ); the other three leptons are neutrinos ( ν e , ν μ , ν τ ), which are

6142-501: The other common elementary particles (such as electrons, neutrinos, or weak bosons) are so light or so rare when compared to atomic nuclei, we can neglect their mass contribution to the observable universe's total mass. Therefore, one can conclude that most of the visible mass of the universe consists of protons and neutrons, which, like all baryons , in turn consist of up quarks and down quarks. Some estimates imply that there are roughly 10 baryons (almost entirely protons and neutrons) in

6225-430: The same quantum state ( Pauli exclusion principle ). Also, bosons can be either elementary, like photons, or a combination, like mesons . The spin of bosons are integers instead of half integers. Gluons mediate the strong interaction , which join quarks and thereby form hadrons , which are either baryons (three quarks) or mesons (one quark and one antiquark). Protons and neutrons are baryons, joined by gluons to form

6308-448: 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

6391-399: The small droplets can undergo a phase transition at a time, the detector can stay active for much longer periods. When enough energy is deposited in a droplet by ionizing radiation, the superheated droplet becomes a gas bubble. The bubble development is accompanied by an acoustic shock wave that is picked up by piezo-electric sensors. The main advantage of the bubble detector technique is that

6474-452: 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. PICO is an expansion of the concept planned in 2015. Other types of detectors – Time projection chambers (TPCs) filled with low pressure gases are being studied for WIMP detection. The Directional Recoil Identification From Tracks (DRIFT) collaboration

6557-399: The surrounding gluons, slight differences in the calculation make large differences in the masses. There are also 12 fundamental fermionic antiparticles that correspond to these 12 particles. For example, the antielectron (positron) e is the electron's antiparticle and has an electric charge of +1  e . Isolated quarks and antiquarks have never been detected,

6640-409: The universe at any given moment). String theory proposes that our universe is merely a 4-brane, inside which exist the three space dimensions and the one time dimension that we observe. The remaining 7 theoretical dimensions either are very tiny and curled up (and too small to be macroscopically accessible) or simply do not/cannot exist in our universe (because they exist in a grander scheme called

6723-492: The use of scientific 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

6806-405: The visible universe (not including dark matter ), mostly photons and other massless force carriers. The Standard Model of particle physics contains 12 flavors of elementary fermions , plus their corresponding antiparticles , as well as elementary bosons that mediate the forces and the Higgs boson , which was reported on July 4, 2012, as having been likely detected by the two main experiments at

6889-452: Was confirmed after the final data run ended in May 2016. 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 CDMS-Si ). In February 2010, researchers at CDMS announced that they had observed two events that may have been caused by WIMP-nucleus collisions. CoGeNT ,

#923076