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73-533: The original TPC was invented by David R. Nygren , an American physicist, at Lawrence Berkeley Laboratory in the late 1970s. Its first major application was in the PEP-4 detector, which studied 29 GeV electron–positron collisions at the PEP storage ring at SLAC . A time projection chamber consists of a gas -filled detection volume in an electric field with a position-sensitive electron collection system. The original design (and

146-456: A Presidential Distinguished Professor of Physics at the University of Texas at Arlington . He has worked at Lawrence Berkeley National Laboratory since 1973. He has been called "the most distinguished developer of particle detection instruments in the country". Nygren earned his B.A. degree at Whitman College in 1960, and his Ph.D. at the University of Washington in 1967. He is a fellow of

219-400: A beta decay reaction may interact in a distant detector as a muon or tau neutrino, as defined by the flavor of the charged lepton produced in the detector. This oscillation occurs because the three mass state components of the produced flavor travel at slightly different speeds, so that their quantum mechanical wave packets develop relative phase shifts that change how they combine to produce

292-408: A consequence. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. The three mass values are not yet known as of 2024, but laboratory experiments and cosmological observations have determined the differences of their squares, an upper limit on their sum (<  2.14 × 10  kg ), and an upper limit on the mass of

365-447: A detector by a factor of around one thousand. This feature is particularly useful in neutrino physics, where neutrino– nucleon interaction cross sections are small. The body of a typical LArTPC is formed of three parts. On one side of the detector is a high- voltage cathode plane, used to establish a drift electric field across the TPC. Although the exact electric potential at which this

438-628: A difference between the neutrino and antineutrino could simply be due to one particle with two possible chiralities. As of 2019 , it is not known whether neutrinos are Majorana or Dirac particles. It is possible to test this property experimentally. For example, if neutrinos are indeed Majorana particles, then lepton-number violating processes such as neutrinoless double-beta decay would be allowed, while they would not if neutrinos are Dirac particles. Several experiments have been and are being conducted to search for this process, e.g. GERDA , EXO , SNO+ , and CUORE . The cosmic neutrino background

511-472: A few millimeters, and the angle at which the wires are oriented relative to the vertical varies from plane to plane. Together, these planes read out signals from the drift electrons. For a detector with N anode wire planes, the inner N  − 1 planes are called induction planes. These are set at lower (more negative) potentials than the outer plane, allowing drift electrons to pass through them, inducing signals that are used for event reconstruction. The outer plane

584-415: A function of time is the "signal" that is passed to the event reconstruction. For a given anode plane wire, the signal produced will have a specific form that depends on whether the wire is located in an induction plane or in a collection plane. As a drift electron moves toward a wire in an induction plane, it induces a current in the wire, producing a "bump" in output current. As the electron moves away from

657-499: A gamma ray. The coincidence of both events—positron annihilation and neutron capture—gives a unique signature of an antineutrino interaction. In February 1965, the first neutrino found in nature was identified by a group including Frederick Reines and Friedel Sellschop . The experiment was performed in a specially prepared chamber at a depth of 3 km in the East Rand ("ERPM") gold mine near Boksburg , South Africa. A plaque in

730-593: A laboratory, but is predicted to happen within stars and supernovae. The process affects the abundance of isotopes seen in the universe . Neutrino-induced disintegration of deuterium nuclei has been observed in the Sudbury Neutrino Observatory, which uses a heavy water detector. There are three known types ( flavors ) of neutrinos: electron neutrino ν e , muon neutrino ν μ , and tau neutrino ν τ , named after their partner leptons in

803-468: A new major field of research that still continues. Eventual confirmation of the phenomenon of neutrino oscillation led to two Nobel prizes, one to R. Davis , who conceived and led the Homestake experiment and Masatoshi Koshiba of Kamiokande, whose work confirmed it, and one to Takaaki Kajita of Super-Kamiokande and A.B. McDonald of Sudbury Neutrino Observatory for their joint experiment, which confirmed

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876-566: A process analogous to light traveling through a transparent material . This process is not directly observable because it does not produce ionizing radiation , but gives rise to the Mikheyev–Smirnov–Wolfenstein effect . Only a small fraction of the neutrino's energy is transferred to the material. Onia For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has no electric charge and half-integer spin. They are distinguished from

949-418: A proton, electron, and the smaller neutral particle (now called an electron antineutrino ): Fermi's paper, written in 1934, unified Pauli's neutrino with Paul Dirac 's positron and Werner Heisenberg 's neutron–proton model and gave a solid theoretical basis for future experimental work. By 1934, there was experimental evidence against Bohr's idea that energy conservation is invalid for beta decay: At

1022-430: A segmented anode plate with either just a Frisch grid or an active electron-multiplication element like a gas electron multiplier . These newer TPCs also depart from the traditional geometry of a cylinder with an axial field in favour of a flat geometry or a cylinder with a radial field. Earlier researchers in particle physics also usually made use of a more simplified box-shaped geometry arranged directly above or below

1095-605: A varying superposition of three flavors. Each flavor component thereby oscillates as the neutrino travels, with the flavors varying in relative strengths. The relative flavor proportions when the neutrino interacts represent the relative probabilities for that flavor of interaction to produce the corresponding flavor of charged lepton. There are other possibilities in which neutrinos could oscillate even if they were massless: If Lorentz symmetry were not an exact symmetry, neutrinos could experience Lorentz-violating oscillations . Neutrinos traveling through matter, in general, undergo

1168-455: A wire, it induces a current in the opposite direction, producing an output "bump" of the opposite sign as the first. The result is a bipolar signal. In contrast, signals for a collection plane wire are unipolar, since electrons do not pass by the wire but are instead "collected" by it. For both of these geometries, a larger signal amplitude implies that more drift electrons either passed by the wire (for induction planes) or were collected by it (for

1241-407: Is advantageous as a sensitive medium for several reasons. The fact that argon is a noble element and therefore has a vanishing electronegativity means that electrons produced by ionizing radiation will not be absorbed as they drift toward the detector readout. Argon also scintillates when an energetic charged particle passes by, releasing a number of scintillation photons that is proportional to

1314-468: Is also a probe of whether neutrinos are Majorana particles , since there should be a different number of cosmic neutrinos detected in either the Dirac or Majorana case. Neutrinos can interact with a nucleus, changing it to another nucleus. This process is used in radiochemical neutrino detectors . In this case, the energy levels and spin states within the target nucleus have to be taken into account to estimate

1387-545: Is associated with the correspondingly named charged lepton . Although neutrinos were long believed to be massless, it is now known that there are three discrete neutrino masses with different tiny values (the smallest of which could even be zero ), but the three masses do not uniquely correspond to the three flavors: A neutrino created with a specific flavor is a specific mixture of all three mass states (a quantum superposition ). Similar to some other neutral particles , neutrinos oscillate between different flavors in flight as

1460-405: Is called the collection plane because the drift electrons are collected on these wires, producing additional signals. Having multiple planes with different wire orientations permits two-dimensional event reconstruction, while the third dimension is found from electron drift times. The third part is a field cage between the cathode and anode. This field cage maintains a uniform electric field between

1533-493: Is conventionally called the "normal hierarchy", while in the "inverted hierarchy", the opposite would hold. Several major experimental efforts are underway to help establish which is correct. A neutrino created in a specific flavor eigenstate is in an associated specific quantum superposition of all three mass eigenstates. The three masses differ so little that they cannot possibly be distinguished experimentally within any practical flight path. The proportion of each mass state in

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1606-460: Is important to understand because many neutrinos emitted by fusion in the Sun pass through the dense matter in the solar core (where essentially all solar fusion takes place) on their way to detectors on Earth. Starting in 1998, experiments began to show that solar and atmospheric neutrinos change flavors (see Super-Kamiokande and Sudbury Neutrino Observatory ). This resolved the solar neutrino problem:

1679-533: Is no experimental evidence for a non-zero magnetic moment in neutrinos. Weak interactions create neutrinos in one of three leptonic flavors : electron neutrinos ( ν e ), muon neutrinos ( ν μ ), or tau neutrinos ( ν τ ), associated with the corresponding charged leptons, the electron ( e ), muon ( μ ), and tau ( τ ), respectively. Although neutrinos were long believed to be massless, it

1752-456: Is now known that there are three discrete neutrino masses; each neutrino flavor state is a linear combination of the three discrete mass eigenstates. Although only differences of squares of the three mass values are known as of 2016, experiments have shown that these masses are tiny compared to any other particle. From cosmological measurements, it has been calculated that the sum of the three neutrino masses must be less than one-millionth that of

1825-443: Is set is dependent on the detector geometry, this high-voltage cathode typically produces a drift field of 500 V/cm across the detector. On the side opposite of the cathode plane is a set of anode wire planes set at potentials much higher (less negative) than that of the cathode. Each plane is separated from its neighbors by a small gap, usually on the order of 1 cm. A plane consists of many parallel conducting wires spaced by

1898-595: Is so small ( -ino ) that it was long thought to be zero . The rest mass of the neutrino is much smaller than that of the other known elementary particles (excluding massless particles ). The weak force has a very short range, the gravitational interaction is extremely weak due to the very small mass of the neutrino, and neutrinos do not participate in the electromagnetic interaction or the strong interaction . Thus, neutrinos typically pass through normal matter unimpeded and undetected. Weak interactions create neutrinos in one of three leptonic flavors : Each flavor

1971-475: The 1995 Nobel Prize . In this experiment, now known as the Cowan–Reines neutrino experiment , antineutrinos created in a nuclear reactor by beta decay reacted with protons to produce neutrons and positrons: The positron quickly finds an electron, and they annihilate each other. The two resulting gamma rays (γ) are detectable. The neutron can be detected by its capture on an appropriate nucleus, releasing

2044-564: The American Physical Society . This article about an American physicist is a stub . You can help Misplaced Pages by expanding it . Neutrino A neutrino ( / nj uː ˈ t r iː n oʊ / new- TREE -noh ; denoted by the Greek letter ν ) is an elementary particle that interacts via the weak interaction and gravity . The neutrino is so named because it is electrically neutral and because its rest mass

2117-451: The Solvay conference of that year, measurements of the energy spectra of beta particles (electrons) were reported, showing that there is a strict limit on the energy of electrons from each type of beta decay. Such a limit is not expected if the conservation of energy is invalid, in which case any amount of energy would be statistically available in at least a few decays. The natural explanation of

2190-509: The Standard Model (see table at right). The current best measurement of the number of neutrino types comes from observing the decay of the Z boson . This particle can decay into any light neutrino and its antineutrino, and the more available types of light neutrinos, the shorter the lifetime of the Z ;boson. Measurements of the Z lifetime have shown that three light neutrino flavors couple to

2263-517: The Waste Isolation Pilot Plant (WIPP) site near Carlsbad, New Mexico in Fall, 2010. Dark Matter Time Projection Chamber published first results from a surface run in 2010, setting a spin-dependent cross section limit. David R. Nygren David Robert Nygren (born December 30, 1938) is a particle physicist known for his invention of the time projection chamber . He is currently

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2336-465: The anode wires in the azimuthal direction, θ , which provides information on the radial coordinate, r . To obtain the azimuthal direction, each cathode plane is divided into strips along the radial direction. In recent years other means of position-sensitive electron amplification and detection have become more widely used, especially in conjunction with the increased application of time projection chambers in nuclear physics . These usually combine

2409-515: The cosmic neutrino background (CNB). R. Davis and M. Koshiba were jointly awarded the 2002 Nobel Prize in Physics. Both conducted pioneering work on solar neutrino detection, and Koshiba's work also resulted in the first real-time observation of neutrinos from the SN 1987A supernova in the nearby Large Magellanic Cloud . These efforts marked the beginning of neutrino astronomy . SN 1987A represents

2482-515: The muon neutrino (already hypothesised with the name neutretto ), which earned them the 1988 Nobel Prize in Physics . When the third type of lepton, the tau , was discovered in 1975 at the Stanford Linear Accelerator Center , it was also expected to have an associated neutrino (the tau neutrino). The first evidence for this third neutrino type came from the observation of missing energy and momentum in tau decays analogous to

2555-405: The proton and the electron . He considered that the new particle was emitted from the nucleus together with the electron or beta particle in the process of beta decay and had a mass similar to the electron. James Chadwick discovered a much more massive neutral nuclear particle in 1932 and named it a neutron also, leaving two kinds of particles with the same name. The word "neutrino" entered

2628-449: The 2015 Nobel Prize for Physics for their landmark finding, theoretical and experimental, that neutrinos can change flavors. As well as specific sources, a general background level of neutrinos is expected to pervade the universe, theorized to occur due to two main sources. Around 1 second after the Big Bang , neutrinos decoupled, giving rise to a background level of neutrinos known as

2701-530: The Z. The correspondence between the six quarks in the Standard Model and the six leptons, among them the three neutrinos, suggests to physicists' intuition that there should be exactly three types of neutrino. There are several active research areas involving the neutrino with aspirations of finding: International scientific collaborations install large neutrino detectors near nuclear reactors or in neutrino beams from particle accelerators to better constrain

2774-481: The beam line, such as in the CERN NA49 and NA35 experiments. In 1974, William J. Willis and Veljko Radeka demonstrated that total absorption calorimetry was possible in liquid argon detectors without the amplification that normally occurs in a gaseous ionization detector . This critical technology enabled the possibility of a time projection chamber based on Nygren's original design, but using liquid argon as

2847-525: The beta decay leading to the discovery of the electron neutrino. The first detection of tau neutrino interactions was announced in 2000 by the DONUT collaboration at Fermilab ; its existence had already been inferred by both theoretical consistency and experimental data from the Large Electron–Positron Collider . In the 1960s, the now-famous Homestake experiment made the first measurement of

2920-471: The beta decay spectrum as first measured in 1934 was that only a limited (and conserved) amount of energy was available, and a new particle was sometimes taking a varying fraction of this limited energy, leaving the rest for the beta particle. Pauli made use of the occasion to publicly emphasize that the still-undetected "neutrino" must be an actual particle. The first evidence of the reality of neutrinos came in 1938 via simultaneous cloud-chamber measurements of

2993-515: The cathode and the anode, so that drift electron trajectories deviate as little as possible from the shortest path between the point of ionization and the anode plane. This is intended to prevent distortion of particle trajectory during event reconstruction. A light-collection system often accompanies the basic LArTPC as a means of extracting more information from an event by scintillation light. It can also play an important role in triggering, because it collects scintillation light only nanoseconds after

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3066-441: The collection plane). The signal readout of all of the wires in a given anode plane can be organized into a 2D picture of a particle interaction. Such a picture is a projection of the 3D particle interaction onto a 2D plane whose normal vector is parallel to the wires in the specified anode plane. The 2D projections corresponding to each of the anode planes are combined to fully reconstruct the 3D interaction. The technique itself

3139-409: The concept. For the case of neutrinos this theory has gained popularity as it can be used, in combination with the seesaw mechanism , to explain why neutrino masses are so small compared to those of the other elementary particles, such as electrons or quarks. Majorana neutrinos would have the property that the neutrino and antineutrino could be distinguished only by chirality; what experiments observe as

3212-461: The context of preventing the proliferation of nuclear weapons . Because antineutrinos and neutrinos are neutral particles, it is possible that they are the same particle. Rather than conventional Dirac fermions , neutral particles can be another type of spin  ⁠ 1  / 2 ⁠ particle called Majorana particles , named after the Italian physicist Ettore Majorana who first proposed

3285-452: The diffusion of the electrons coming from the ionization of the gas. On passing through the detector gas, a particle will produce primary ionization along its track. The z coordinate (along the cylinder axis) is determined by measuring the drift time from the ionization event to the MWPC at the end. This is done using the usual technique of a drift chamber . The MWPC at the end is arranged with

3358-416: The drift volume. In a typical LArTPC, each wire in each anode plane is part of an RC circuit , with the wire itself located between the resistor and capacitor . The other end of the resistor is wired to a bias voltage, and the other end of the capacitor is wired to the front-end electronics. The front-end electronics amplify and digitize the current in the circuit. This amplified and digitized current as

3431-417: The electron and the recoil of the nucleus. In 1942, Wang Ganchang first proposed the use of beta capture to experimentally detect neutrinos. In the 20 July 1956 issue of Science , Clyde Cowan , Frederick Reines , Francis B. "Kiko" Harrison, Herald W. Kruse, and Austin D. McGuire published confirmation that they had detected the neutrino, a result that was rewarded almost forty years later with

3504-728: The electron neutrino. Neutrinos are fermions with spin of ⁠ 1  / 2 ⁠ . For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has spin of ⁠ 1  / 2 ⁠ and no electric charge. Antineutrinos are distinguished from neutrinos by having opposite-signed lepton number and weak isospin , and right-handed instead of left-handed chirality. To conserve total lepton number (in nuclear beta decay), electron neutrinos only appear together with positrons (anti-electrons) or electron-antineutrinos, whereas electron antineutrinos only appear with electrons or electron neutrinos. Neutrinos are created by various radioactive decays ;

3577-405: The electron neutrinos produced in the Sun had partly changed into other flavors which the experiments could not detect. Although individual experiments, such as the set of solar neutrino experiments, are consistent with non-oscillatory mechanisms of neutrino flavor conversion, taken altogether, neutrino experiments imply the existence of neutrino oscillations. Especially relevant in this context are

3650-451: The electron. More formally, neutrino flavor eigenstates (creation and annihilation combinations) are not the same as the neutrino mass eigenstates (simply labeled "1", "2", and "3"). As of 2024, it is not known which of these three is the heaviest. The neutrino mass hierarchy consists of two possible configurations. In analogy with the mass hierarchy of the charged leptons, the configuration with mass 2 being lighter than mass 3

3723-455: The energy deposited in the argon by the passing particle. Liquid argon is also relatively inexpensive, making large-scale projects economically feasible. However, one of the primary motivations for using liquid argon as a sensitive medium is its density. Liquid argon is around one thousand times denser than the gas used in Nygren's TPC design, which increases the likelihood of a particle interacting in

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3796-600: The existence of all three neutrino flavors and found no deficit. A practical method for investigating neutrino oscillations was first suggested by Bruno Pontecorvo in 1957 using an analogy with kaon oscillations; over the subsequent 10 years, he developed the mathematical formalism and the modern formulation of vacuum oscillations. In 1985 Stanislav Mikheyev and Alexei Smirnov (expanding on 1978 work by Lincoln Wolfenstein ) noted that flavor oscillations can be modified when neutrinos propagate through matter. This so-called Mikheyev–Smirnov–Wolfenstein effect (MSW effect)

3869-477: The flux of electron neutrinos arriving from the core of the Sun and found a value that was between one third and one half the number predicted by the Standard Solar Model . This discrepancy, which became known as the solar neutrino problem , remained unresolved for some thirty years, while possible problems with both the experiment and the solar model were investigated, but none could be found. Eventually, it

3942-447: The following list is not exhaustive, but includes some of those processes: The majority of neutrinos which are detected about the Earth are from nuclear reactions inside the Sun. At the surface of the Earth, the flux is about 65 billion ( 6.5 × 10 ) solar neutrinos , per second per square centimeter. Neutrinos can be used for tomography of the interior of the Earth. The neutrino

4015-593: The hydrogen nuclei in the water molecules. A hydrogen nucleus is a single proton, so simultaneous nuclear interactions, which would occur within a heavier nucleus, do not need to be considered for the detection experiment. Within a cubic meter of water placed right outside a nuclear reactor, only relatively few such interactions can be recorded, but the setup is now used for measuring the reactor's plutonium production rate. Very much like neutrons do in nuclear reactors , neutrinos can induce fission reactions within heavy nuclei . So far, this reaction has not been measured in

4088-513: The initial state, then the final state has only matched lepton and anti-lepton pairs: electron neutrinos appear in the final state together with only positrons (anti-electrons) or electron antineutrinos, and electron antineutrinos with electrons or electron neutrinos. Antineutrinos are produced in nuclear beta decay together with a beta particle (in beta decay a neutron decays into a proton, electron, and antineutrino). All antineutrinos observed thus far had right-handed helicity (i.e., only one of

4161-500: The main building commemorates the discovery. The experiments also implemented a primitive neutrino astronomy and looked at issues of neutrino physics and weak interactions. The antineutrino discovered by Clyde Cowan and Frederick Reines was the antiparticle of the electron neutrino. In 1962, Leon M. Lederman , Melvin Schwartz , and Jack Steinberger showed that more than one type of neutrino exists by first detecting interactions of

4234-588: The most favored candidates for dark matter . The experiment uses a low-pressure time projection chamber in order to extract the original direction of potential dark matter events. The collaboration includes physicists from the Massachusetts Institute of Technology (MIT), Boston University (BU), Brandeis University , and Royal Holloway University of London . Several prototype detectors have been built and tested in laboratories at MIT and BU. The collaboration took its first data in an underground laboratory at

4307-504: The neutrino masses and the values for the magnitude and rates of oscillations between neutrino flavors. These experiments are thereby searching for the existence of CP violation in the neutrino sector; that is, whether or not the laws of physics treat neutrinos and antineutrinos differently. The KATRIN experiment in Germany began to acquire data in June 2018 to determine the value of the mass of

4380-404: The neutrinos by having opposite signs of lepton number and opposite chirality (and consequently opposite-sign weak isospin). As of 2016, no evidence has been found for any other difference. So far, despite extensive and continuing searches for exceptions, in all observed leptonic processes there has never been any change in total lepton number; for example, if the total lepton number is zero in

4453-435: The one most commonly used) is a cylindrical chamber with multi-wire proportional chambers (MWPC) as endplates. Along its length, the chamber is divided into halves by means of a central high-voltage electrode disc, which establishes an electric field between the center and the end plates. Furthermore, a magnetic field is often applied along the length of the cylinder, parallel to the electric field, in order to minimize

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4526-466: The only means by which a LArTPC can identify a trigger time, they are necessary for studying phenomena like supernovae and proton decay, where the particles undergoing decay or interaction are not produced in a human-made accelerator and the timing of a beam of particles is therefore not known. Photomultiplier tubes , light guides, and silicon photomultipliers are examples of instruments used to collect this light. These are typically positioned just outside

4599-578: The only verified detection of neutrinos from a supernova. However, many stars have gone supernova in the universe, leaving a theorized diffuse supernova neutrino background . Neutrinos have half-integer spin ( ⁠ 1  / 2 ⁠ ħ ); therefore they are fermions . Neutrinos are leptons. They have only been observed to interact through the weak force , although it is assumed that they also interact gravitationally. Since they have non-zero mass, theoretical considerations permit neutrinos to interact magnetically, but do not require them to. As yet there

4672-450: The particle passes through the detector. This is comparatively (on the order of 1000 times) shorter than the time taken by the freed electrons to drift to the wire planes, so it is often sufficient to demarcate the collection time of scintillation photons as a trigger time ( t 0 ) for an event. With this trigger time, one can then find electron drift times, which enables three-dimensional reconstruction of an event. While such systems are not

4745-409: The probability for an interaction. In general the interaction probability increases with the number of neutrons and protons within a nucleus. It is very hard to uniquely identify neutrino interactions among the natural background of radioactivity. For this reason, in early experiments a special reaction channel was chosen to facilitate the identification: the interaction of an antineutrino with one of

4818-684: The pure flavor states produced has been found to depend profoundly on the flavor. The relationship between flavor and mass eigenstates is encoded in the PMNS matrix . Experiments have established moderate- to low-precision values for the elements of this matrix, with the single complex phase in the matrix being only poorly known, as of 2016. A non-zero mass allows neutrinos to possibly have a tiny magnetic moment ; if so, neutrinos would interact electromagnetically, although no such interaction has ever been observed. Neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in

4891-428: The reactor experiment KamLAND and the accelerator experiments such as MINOS . The KamLAND experiment has indeed identified oscillations as the neutrino flavor conversion mechanism involved in the solar electron neutrinos. Similarly MINOS confirms the oscillation of atmospheric neutrinos and gives a better determination of the mass squared splitting. Takaaki Kajita of Japan, and Arthur B. McDonald of Canada, received

4964-910: The scientific vocabulary through Enrico Fermi , who used it during a conference in Paris in July ;1932 and at the Solvay Conference in October ;1933, where Pauli also employed it. The name (the Italian equivalent of "little neutral one") was jokingly coined by Edoardo Amaldi during a conversation with Fermi at the Institute of Physics of via Panisperna in Rome, in order to distinguish this light neutral particle from Chadwick's heavy neutron. In Fermi's theory of beta decay , Chadwick's large neutral particle could decay to

5037-651: The sensitive medium instead of gas. In 1976, Herbert H. Chen , with collaborators at University of California, Irvine and the California Institute of Technology , proposed one of the earliest uses of liquid argon in a time projection chamber (LArTPC). Chen's initial goals with such a detector were to study neutrino-elecron scattering, but the goals evolved to measure solar or cosmic neutrinos or proton decay. In 1977, Carlo Rubbia independently, and nearly simultaneously, proposed to construct an LArTPC at CERN for rare event particle physics experiments. Liquid argon

5110-449: The two possible spin states has ever been seen), while neutrinos were all left-handed. Antineutrinos were first detected as a result of their interaction with protons in a large tank of water. This was installed next to a nuclear reactor as a controllable source of the antineutrinos (see Cowan–Reines neutrino experiment ). Researchers around the world have begun to investigate the possibility of using antineutrinos for reactor monitoring in

5183-420: Was first developed for radiation detection using argon in the early 1970s. The ZEPLIN programme pioneered the use of two-phase technology for WIMP searches. The XENON and LUX series of detectors represent the state-of the art implementation of this instrument in physics. The Dark Matter Time Projection Chamber is an experiment for direct detection of weakly interacting massive particles (WIMPs), one of

5256-423: Was postulated first by Wolfgang Pauli in 1930 to explain how beta decay could conserve energy , momentum , and angular momentum ( spin ). In contrast to Niels Bohr , who proposed a statistical version of the conservation laws to explain the observed continuous energy spectra in beta decay , Pauli hypothesized an undetected particle that he called a "neutron", using the same -on ending employed for naming both

5329-404: Was realized that both were actually correct and that the discrepancy between them was due to neutrinos being more complex than was previously assumed. It was postulated that the three neutrinos had nonzero and slightly different masses, and could therefore oscillate into undetectable flavors on their flight to the Earth. This hypothesis was investigated by a new series of experiments, thereby opening

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