Neutrino

Composition	Elementary particle
Family	Fermion
Group	Lepton
Interaction	weak interaction and gravitation
Antiparticle	Antineutrino (possibly identical to the neutrino)
Theorized	1930 by Wolfgang Pauli
Discovered	1956 by Clyde Cowan, Frederick Reines, F. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature Gravitation is a natural Phenomenon by which objects with Mass attract one another to most kinds of particles, there is an associated antiparticle with the same Mass and opposite Electric charge. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. Clyde Lorrain Cowan Jr ( December 6, 1919 &ndash May 24, 1974) was the co-discoverer of the Neutrino Frederick Reines ( March 16 1918 – August 26 1998) was an American Physicist. B. Harrison, H. W. Kruse, and A. D. McGuire.
Symbol	νe, νμ and ντ
No. of types	3 - electron, muon and tau
Electric charge	0
Color charge	0
Spin	1/2
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Neutrinos are elementary particles that travel close to the speed of light, lack an electric charge, are able to pass through ordinary matter almost undisturbed and are thus extremely difficult to detect. The elementary charge, usually denoted e, is the Electric charge carried by a single Proton, or equivalently the negative of the electric charge carried In Particle physics, color charge is a property of Quarks and Gluons which are related to their Strong interactions in the context of Quantum In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. As of 1999, it is believed neutrinos have a minuscule, but nonzero mass. Year 1999 ( MCMXCIX) was a Common year starting on Friday (link will display full 1999 Gregorian calendar) Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object They are usually denoted by the Greek letter (nu). Nu (uppercase Ν, lowercase ν; Νι Ni is the 13th letter of the Greek alphabet.

Neutrinos are created as a result of certain types of radioactive decay or nuclear reactions such as those that take place in the Sun, in nuclear reactors, or when cosmic rays hit atoms. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. The Sun (Sol is the Star at the center of the Solar System. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on There are three types, or "flavors", of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos; each type also has an antimatter partner, called an antineutrino. In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. Electron neutrinos or antineutrinos are generated whenever neutrons change into protons or vice versa, the two forms of beta decay. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted Interactions involving neutrinos are generally mediated by the weak force. The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature

Most neutrinos passing through the Earth emanate from the sun, and more than 50 trillion solar electron neutrinos pass through the human body every second^[1].

Contents 1 History 2 Properties 2.1 Popular Misconception 2.2 Types of neutrinos 2.3 Flavor oscillations 2.4 Speed 2.5 Mass 2.6 Handedness 2.7 Trivia 3 Neutrino sources 3.1 Artificially produced neutrinos 3.2 Geologically produced neutrinos 3.3 Atmospheric neutrinos 3.4 Solar neutrinos 3.5 Supernovae 3.6 Cosmic background radiation 4 Neutrino detection 5 Motivation for scientific interest in the neutrino 6 See also 7 Notes 8 References 9 External links

History

The neutrino was first postulated in December 1930 by Wolfgang Pauli to preserve conservation of energy, conservation of momentum, and conservation of angular momentum in beta decay, the decay of a neutron into a proton, an electron and an antineutrino. In Physics, the law of conservation of energy states that the total amount of Energy in an isolated system remains constant and cannot be created although it may In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Pauli theorized that an undetected particle was carrying away the observed difference between the energy, momentum, and angular momentum of the initial and final particles. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position

The current name neutrino was coined by Enrico Fermi, who developed the first theory describing neutrino interactions, as a pun on neutrone, the Italian name of the neutron: neutrone seems to use the -one suffix (even though it is a complete word, not a compound), which in Italian indicates a large object, whereas -ino indicates a small one. A pun (or paronomasia) is a Phrase that deliberately exploits confusion between similar-sounding Words for humorous or Rhetorical Italian ( or lingua italiana) is a Romance language spoken by about 63 million people as a First language, primarily in Italy. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron.

In 1942 Kan-Chang Wang first proposed to use beta-capture to experimentally detect neutrinos. Kan-Chang Wang ( ( May 28 1907 - December 10 1998) was a nuclear Physicist from China. ^[2] In 1956 Clyde Cowan, Frederick Reines, F. Clyde Lorrain Cowan Jr ( December 6, 1919 &ndash May 24, 1974) was the co-discoverer of the Neutrino Frederick Reines ( March 16 1918 – August 26 1998) was an American Physicist. B. Harrison, H. W. Kruse, and A. D. McGuire published the article "Detection of the Free Neutrino: a Confirmation" in Science, a result that was rewarded with the 1995 Nobel Prize. Science is the Academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious Scientific The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. In this experiment, now known as the neutrino experiment, neutrinos created in a nuclear reactor by beta decay were shot into protons producing neutrons and positrons both of which could be detected. The neutrino experiment, also called the Cowan and Reines neutrino experiment, was performed by Clyde L This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. It is now known that both the proposed and the observed particles were antineutrinos.

In 1962 Leon M. Lederman, Melvin Schwartz and Jack Steinberger showed that more than one type of neutrino exists by first detecting interactions of the muon neutrino (already hypothesised with the name neutretto^[3]), which earned them the 1988 Nobel Prize. Leon Max Lederman (born July 15, 1922) is an American Experimental physicist and Nobel Prize in Physics laureate for Melvin Schwartz ( November 2, 1932 – August 28, 2006) was an American Physicist. Jack Steinberger (born May 25, 1921) is a German - American Physicist currently residing near Geneva Switzerland The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. When a third type of lepton, the tau, was discovered in 1975 at the Stanford Linear Accelerator, it too was expected to have an associated neutrino. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their The tau lepton (often called the tau, tau particle, or occasionally the tauon; symbol) is a negatively charged Elementary particle with The Stanford Linear Accelerator Center ( SLAC) is a United States Department of Energy National Laboratory operated by Stanford University under First evidence for this third neutrino type came from the observation of missing energy and momentum in tau decays analogous to the beta decay leading to the discovery of the neutrino. The first detection of tau neutrino interactions was announced in summer of 2000 by the DONUT collaboration at Fermilab, making it the latest particle of the Standard Model to have been directly observed; its existence had already inferred both by theoretical consistency, as well as by experimental data from LEP. DONUT ( D irect O bservation of the NU T au E872 was an experiment at Fermilab dedicated to the search for Fermi National Accelerator Laboratory ( Fermilab) located in Batavia near Chicago, Illinois, is a U The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles

Starting in the late 1960s, several experiments found that the number of electron neutrinos arriving from the sun was between one third and one half the number predicted by the Standard Solar Model, a discrepancy which became known as the solar neutrino problem and remained unresolved for some thirty years. The Standard Solar Model (SSM is the best current physical model of our Sun. Introduction The Sun is a natural Nuclear fusion reactor powered by a Proton-proton chain reaction which converts four Hydrogen nuclei

The Standard Model of particle physics assumes massless neutrinos that don't change flavor. However, nonzero neutrino mass and accompanying flavor oscillation remained a possibility.

A practical method for investigating neutrino masses (that is, flavor oscillation) was first suggested by Bruno Pontecorvo in 1957 using an analogy with the neutral kaon system; over the subsequent 10 years he developed the mathematical formalism and the modern formulation of vacuum oscillations. Bruno Pontecorvo russian Бруно Понтекорво (Marina di Pisa Italy August 22, 1913 - Dubna Russia September 24, 1993 In Particle physics, a kaon (/ˈkeɪɒn/ also called K-meson and denoted) is any one of a group of four Mesons distinguished by the fact that they 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. Stanislav Pavlovich Mikeyev (Станислав Павлович Михеев is a Russian physicist best known as one of the discoverers of the MSW effect. Lincoln Wolfenstein (born 1923 is an American particle Physicist who studies the Weak interaction. This so-called MSW effect is important to understand neutrinos emitted by the Sun, which pass through its dense atmosphere on their way to detectors on Earth. The Mikheyev-Smirnov-Wolfenstein effect (often referred to as matter effect) is a Particle physics process which can act to modify Neutrino oscillations

Starting in 1998, experiments began to show that solar and atmospheric neutrinos change flavors (see Super-Kamiokande, Sudbury Neutrino Observatory). Super-Kamiokande, or Super-K for short is a neutrino observatory in the city of Hida, Gifu Prefecture, Japan. The Sudbury Neutrino Observatory ( SNO) is a Neutrino observatory located 6800 feet (about 2 km underground in Vale Inco 's Creighton Mine This resolved the solar neutrino problem: 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 the reactor experiment KamLAND and the accelerator experiments such as MINOS. The Kamioka Liquid Scintillator Antineutrino Detector (KamLAND is an experiment at the Kamioka Observatory, an underground Neutrino observatory near Toyama In Greek mythology, Minos ( Ancient Greek:) was a mythical king of Crete son of Zeus and Europa. 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 (Maltoni, 2004).

Raymond Davis Jr. and Masatoshi Koshiba were jointly awarded the 2002 Nobel Prize in Physics. Raymond Davis Jr ( October 14, 1914 &ndash May 31, 2006) was an American Chemist, Physicist, and Nobel Masatoshi Koshiba (小柴 昌俊 Koshiba Masatoshi, born on September 19, 1926 in Toyohashi, Aichi Prefecture) is a Japanese The Nobel Prize in Physics (Nobelpriset i fysik is awarded once a year by the Royal Swedish Academy of Sciences. Ray Davis for his pioneer work on solar neutrinos and Koshiba for the first real time observation of supernova neutrinos. The detection of solar neutrinos, and of neutrinos of SN 1987A supernova in 1987 marked the beginning of neutrino astronomy. SN 1987A was a Supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby A supernova (plural supernovae or supernovas) is a stellar Explosion. Neutrino astronomy is the branch of astronomy that observes astronomical objects with neutrino detectors in special observatories

Properties

The neutrino has half-integer spin () and is therefore a fermion. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. Because it is an electrically neutral lepton, the neutrino interacts neither by way of the strong nor the electromagnetic force, but only through the weak force. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature

An experiment done by C. S. Wu at Columbia University showed that neutrinos always have left-handed chirality. Chien-Shiung Wu ( May 13, 1912 – February 16, 1997) was a Chinese -born American Physicist with an expertise Columbia University is a private University in the United States and a member of the Ivy League. A phenomenon is said to be chiral if it is not identical to its Mirror image (see Chirality)

Detection of neutrinos is challenging and often requires large detection volumes or high intensity artificial neutrino beams.

To date, not very much is experimentally established concerning the interactions of neutrinos with matter.

Popular Misconception

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 a hydrogen nucleus, which is a single proton. It turns out that an antineutrino would travel about 30 light years through water before it undergoes this specific reaction. This doesn't prove in any way that an antineutrino cannot undergo other reactions with matter. But however it led to popular misconceptions like this one:

Because the cross section in weak nuclear interactions is very small, neutrinos can pass through matter almost unhindered. In nuclear and Particle physics, the concept of a cross section is used to express the likelihood of interaction between particles For typical neutrinos produced in the sun (with energies of a few MeV), it would take approximately one light year (~10¹⁶ m) of lead to block half of them. A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly

For example, in later theories, such as the one describing a so called MSW effect, it is thought that most solar neutrinos are interacting with matter inside the sun. The Mikheyev-Smirnov-Wolfenstein effect (often referred to as matter effect) is a Particle physics process which can act to modify Neutrino oscillations

Types of neutrinos

Neutrinos in the Standard Model
of elementary particles

Fermion	Symbol	Mass[4]
Generation 1 (electron)
Electron neutrino		< 2. 2 eV
Electron antineutrino		< 2. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. 2 eV
Generation 2 (muon)
Muon neutrino		< 170 keV
Muon antineutrino		< 170 keV
Generation 3 (tau)
Tau neutrino		< 15. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. 5 MeV
Tau antineutrino		< 15. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. 5 MeV

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 the Standard Model (see table at right). In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 The tau lepton (often called the tau, tau particle, or occasionally the tauon; symbol) is a negatively charged Elementary particle with Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The current best measurement of the number of neutrino types comes from observing the decay of the Z boson. The W and Z bosons are the Elementary particles that mediate the Weak force. This particle can decay into any light neutrino and its antineutrino, and the more types of light neutrinos available, the shorter the lifetime of the Z boson. Measurements of the Z lifetime have shown that the number of light neutrino types (with "light" meaning of less than half the Z mass) is 3. ^[5] 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. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles However, actual proof that there are only three kinds of neutrinos remains an elusive goal of particle physics.

The possibility of sterile neutrinos — relatively light neutrinos which do not participate in the weak interaction but which could be created through flavor oscillation (see below) — is unaffected by these Z-boson-based measurements, and the existence of such particles is in fact hinted by experimental data from the LSND experiment. A sterile neutrino is a hypothetical Neutrino that does not interact via any of the Fundamental interactions of the Standard Model except gravity The Liquid Scintillator Neutrino Detector (LSND was a Scintillation counter at Los Alamos National Laboratory that measured the number of Neutrinos being However, the currently running MiniBooNE experiment suggested, until recently, that sterile neutrinos are not required to explain the experimental data,^[6] although the latest research into this area is on-going and anomalies in the MiniBooNE data may allow for exotic neutrino types, including sterile neutrinos. MiniBooNE is an experiment at Fermilab designed to observe Neutrino oscillations (BooNE is an acronym for the Booster Neutrino Experiment ^[7]

Flavor oscillations

Main article: Neutrino oscillation

Neutrinos are most often created or detected with a well defined flavor (electron, muon, tau). Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a Neutrino created with a specific Lepton In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their However, in a phenomenon known as neutrino flavor oscillation, neutrinos are able to oscillate between the three available flavors while they propagate through space. Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a Neutrino created with a specific Lepton Specifically, this occurs because the neutrino flavor eigenstates are not the same as the neutrino mass eigenstates (simply called 1, 2, 3). In Mathematics, given a Linear transformation, an of that linear transformation is a nonzero vector which when that transformation is applied to it changes This allows for a neutrino that was produced as an electron neutrino at a given location to have a calculable probability to be detected as either a muon or tau neutrino after it has traveled to another location. This quantum mechanical effect was first hinted by the discrepancy between the number of electron neutrinos detected from the Sun's core failing to match the expected numbers, dubbed as the "solar neutrino problem. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons The Sun (Sol is the Star at the center of the Solar System. Introduction The Sun is a natural Nuclear fusion reactor powered by a Proton-proton chain reaction which converts four Hydrogen nuclei " In the Standard Model the existence of flavor oscillations implies a nonzero neutrino mass, because the amount of mixing between neutrino flavors at a given time depends on the differences in their squared-masses. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles It is possible that the neutrino and antineutrino are in fact the same particle, a hypothesis first proposed by the Italian physicist Ettore Majorana. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. Ettore Majorana ( 5 August 1906, Catania, Sicily, Italy – 27 March 1938 presumed dead) was an The neutrino could transform into an antineutrino (and vice versa) by flipping the orientation of its spin state. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin This change in spin would require the neutrino and antineutrino to have nonzero mass, and therefore travel slower than light, because it can take place only if inertial frames of reference exist that move faster than the particle. In Physics, an inertial frame of reference is a Frame of reference which belongs to a set of frames in which Physical laws hold in the same and simplest

Speed

Before the idea of neutrino oscillations came up, it was generally assumed that neutrinos travel at the speed of light. The question of neutrino velocity is closely related to their mass. In Physics, velocity is defined as the rate of change of Position. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object According to relativity, if neutrinos are massless, they must travel at the speed of light. However, if they carry a mass, they cannot reach the speed of light.

In the early 1980s, first measurements of neutrino speed were done using pulsed pion beams (produced by pulsed proton beams hitting a target). The pions decayed producing neutrinos, and the neutrino interactions observed within a time window in a detector at a distance were consistent with the speed of light. This measurement has been repeated using the MINOS detectors, which found the speed of 3 GeV neutrinos to be (1 − (5. In Greek mythology, Minos ( Ancient Greek:) was a mythical king of Crete son of Zeus and Europa. 1 ± 2. 9)×10⁻⁵) times the speed of light. While the central value is lower than the speed of light, the uncertainty is great enough that it is very likely that the true velocity is too close to the speed of light to see the difference. This measurement set an upper bound on the mass of the muon neutrino of 50 MeV at 99% confidence. ^[8]

The same observation was made, on a somewhat larger scale, with supernova 1987a. SN 1987A was a Supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby The neutrinos from the supernova were detected within a time window that was consistent with a speed of light for the neutrinos. So far, the question of neutrino masses cannot be decided based on measurements of the neutrino speed.

Mass

The Standard Model of particle physics assumes that neutrinos are massless, although adding massive neutrinos to the basic framework is not difficult. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles Indeed, the experimentally established phenomenon of neutrino oscillation requires neutrinos to have nonzero masses. Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a Neutrino created with a specific Lepton ^[6]

The strongest upper limit on the masses of neutrinos comes from cosmology: the Big Bang model predicts that there is a fixed ratio between the number of neutrinos and the number of photons in the cosmic microwave background. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena If the total energy of all three types of neutrinos exceeded an average of 50 electronvolts per neutrino, there would be so much mass in the universe that it would collapse. This limit can be circumvented by assuming that the neutrino is unstable; however, there are limits within the Standard Model that make this difficult. A much more stringent constraint comes from a careful analysis of cosmological data, such as the cosmic microwave background radiation, galaxy surveys and the Lyman-alpha forest. In Astronomy, a redshift survey, or galaxy survey, is a survey of a section of the sky to measure the Redshift of astronomical objects In Astronomical spectroscopy, the Lyman alpha forest is the sum of Absorption lines arising from the Lyman alpha transition of the neutral Hydrogen These indicate that the sum of the neutrino masses must be less than 0. 3 electronvolt (Goobar, 2006).

In 1998, research results at the Super-Kamiokande neutrino detector determined that neutrinos do indeed flavor oscillate, and therefore have mass. Super-Kamiokande, or Super-K for short is a neutrino observatory in the city of Hida, Gifu Prefecture, Japan. The experiment is only sensitive to the difference in the squares of the masses (Mohapatra, 2005).

The best estimate of the difference in the squares of the masses of mass eigenstates 1 and 2 was published by KamLAND in 2005: Δm₂₁² = 0. The Kamioka Liquid Scintillator Antineutrino Detector (KamLAND is an experiment at the Kamioka Observatory, an underground Neutrino observatory near Toyama 000079 eV²

In 2006, the MINOS experiment measured oscillations from an intense muon neutrino beam, determining the difference in the squares of the masses between neutrino mass eigenstates 2 and 3. In Greek mythology, Minos ( Ancient Greek:) was a mythical king of Crete son of Zeus and Europa. The initial results indicate Δm₂₃² = 0. 003 eV², consistent with previous results from Super-K. Super-Kamiokande, or Super-K for short is a neutrino observatory in the city of Hida, Gifu Prefecture, Japan. ^[9]

Currently a number of efforts are under way to directly determine the absolute neutrino mass scale in laboratory experiments. The methods applied involve nuclear beta decay (KATRIN and MARE) or neutrinoless double beta decay (e. KATRIN ( Ka rlsruhe Tri tium N eutrino Experiment is an experiment to measure the Mass of the electron neutrino with sub- eV g. GERDA, CUORE/Cuoricino, NEMO 3 and others).

Handedness

Experimental results show that (nearly) all produced and observed neutrinos have left-handed helicities (spins antiparallel to momenta), and all antineutrinos have right-handed helicities, within the margin of error. In Particle physics, helicity is the projection of the spin \vec S onto the direction of momentum \hat p: h = \vec In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In the massless limit, it means that only one of two possible chiralities is observed for either particle. A phenomenon is said to be chiral if it is not identical to its Mirror image (see Chirality) These are the only chiralities included in the Standard Model of particle interactions. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles

It is possible that their counterparts (right-handed neutrinos and left-handed antineutrinos) simply do not exist. If they do, their properties are substantially different from observable neutrinos and antineutrinos. It is theorized that they are either very heavy (on the order of GUT scale—see Seesaw mechanism), do not participate in weak interaction (so-called sterile neutrinos), or both. The grand unification energy \Lambda_{GUT} or the GUT scale, is the energy level above which it is believed the Electromagnetic force, Weak force In Theoretical physics, in the area of Quantum field theory, the seesaw mechanism is a mechanism to generate very small numbers from "reasonable numbers"

The existence of nonzero neutrino masses somewhat complicates the situation. Neutrinos are produced in weak interactions as chirality eigenstates. However, chirality of a massive particle is not a constant of motion; helicity is, but the chirality operator does not share eigenstates with the helicity operator. Free neutrinos propagate as mixtures of left- and right-handed helicity states, with mixing amplitudes on the order of m_ν / E. This does not significantly affect the experiments, because neutrinos involved are nearly always ultrarelativistic, and thus mixing amplitudes are vanishingly small (for example, most solar neutrinos have energies on the order of 100 keV–1 MeV, so the fraction of neutrinos with "wrong" helicity among them cannot exceed 10^-10). ^[10][11]

Trivia

(This refers to neutrinos associated with electrons, see neutrino flavor. Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost )

In theory, you can construct all isotopes from neutrons and neutrinos, using this method with A neutrons and B neutrinos (B<=A):

A neutrons + B neutrinos => isotope(mass number A, atomic number B)

The resulting isotope would be a neutral atom (i. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The mass number ( A) also called atomic mass number or nucleon number, is the total number of Protons and Neutrons (together known as See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny e. with equal number of protons and electrons). This is true because of the reaction:

neutron + neutrino => proton(el. charge +) + electron(el. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive  Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J  charge -)

Everything else about this reaction is just a matter of energy and chance (how often it happens). In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός

In a reverse process, which is also just a matter of energy, you can disintegrate all isotopes into a cloud of neutrons by shooting antineutrinos at them, like this:

isotope(mass number A, atomic number B) + B antineutrinos => A neutrons

This is listed as trivia here because these types of reactions are expected to happen extremely rarely in nature. In Physics, antineutrinos, the Antiparticles of Neutrinos are neutral particles produced in nuclear Beta decay. Trivia (singular trivium) are unimportant (or "trivial" items especially of information Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe.

Neutrino sources

Artificially produced neutrinos

Nuclear reactors are the major source of human-generated neutrinos. This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled Anti-neutrinos are made in the beta-decay of neutron-rich daughter fragments in the fission process. Generally, the four main isotopes contributing to the anti-neutrino flux are: uranium-235, uranium-238, plutonium-239, plutonium-241 (e. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the g. the anti-neutrinos emitted during beta-minus decay of their respective fission fragments). In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted The average nuclear fission releases about 200 MeV of energy, of which roughly 6% (or 9 MeV, depending on quoted reference) are radiated away as anti-neutrinos. For a typical nuclear reactor with a thermal power of 4,000 MW and an electrical power generation of 1,300 MW, this corresponds to a total power production of 4,250 MW (Mega-Watts), of which 250 MW is radiated away, and disappears, as anti-neutrino radiation. This is to say, 250 MW of fission energy is lost from this reactor and does not appear as heat, since the anti-neutrinos penetrate all normal building materials essentially tracelessly. The exact energy spectrum is mostly uncertain and depends, for example, on the degree to which the fuel is burned.

There is no established experimental method to measure the flux of low energy anti-neutrinos. Only anti-neutrinos with an energy above threshold of 1. 8 MeV can be uniquely identified (see "Neutrino Detection" below). An estimated 3% of all anti-neutrinos from a nuclear reactor carry an energy above this threshold. An average nuclear power plant may generate over 10²⁰ anti-neutrinos per second above this threshold, and a much larger number which cannot be seen with present detector technology.

Some particle accelerators have been used to make neutrino beams. The technique is to smash protons into a fixed target, producing charged pions or kaons. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive In Particle physics, pion (short for pi meson) is the collective name for three Subatomic particles, and. In Particle physics, a kaon (/ˈkeɪɒn/ also called K-meson and denoted) is any one of a group of four Mesons distinguished by the fact that they These unstable particles are then magnetically focused into a long tunnel where they decay while in flight. Because of the relativistic boost of the decaying particle the neutrinos are produced as a beam rather than isotropically. In Physics, the Lorentz transformation converts between two different observers' measurements of space and time where one observer is in constant motion with respect to

Nuclear bombs also produce very large quantities of neutrinos. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Fred Reines and Clyde Cowan considered the detection neutrinos from a bomb prior to their search for reactor neutrinos. Frederick Reines ( March 16 1918 – August 26 1998) was an American Physicist. Clyde Lorrain Cowan Jr ( December 6, 1919 &ndash May 24, 1974) was the co-discoverer of the Neutrino

Geologically produced neutrinos

Neutrinos are produced as a result of natural background radiation. Background radiation is the Ionizing radiation emitted from a variety of natural and artificial Radiation sources In particular, the decay chains of uranium-238 and thorium-232 isotopes, as well as potassium-40, include beta decays which emit anti-neutrinos. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Thorium (ˈθɔːriəm is a Chemical element with the symbol Th and Atomic number 90 Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 In Nuclear physics, beta decay is a type of Radioactive decay in which a Beta particle (an Electron or a Positron) is emitted These so-called geoneutrinos can provide valuable information on the Earth's interior. A first indication for geoneutrinos was found by the KamLAND experiment in 2005. The Kamioka Liquid Scintillator Antineutrino Detector (KamLAND is an experiment at the Kamioka Observatory, an underground Neutrino observatory near Toyama KamLAND's main background in the geoneutrino measurement are the anti-neutrinos coming from reactors. Several future experiments aim at improving the geoneutrino measurement and these will necessarily have to be far away from reactors.

Atmospheric neutrinos

Atmospheric neutrinos result from the interaction of cosmic rays with atomic nuclei in the Earth's atmosphere, creating showers of particles, many of which are unstable and produce neutrinos when they decay. The proton-proton chain reaction is one of several fusion reactions by which Stars convert Hydrogen to Helium, the primary alternative being the For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five A collaboration of particle physicists from Tata Institute of Fundamental Research (TIFR), India, Osaka City University, Japan and Durham University, UK recorded the first cosmic ray neutrino interaction in an underground laboratory in KGF gold mines in India in 1965. Kolar Gold Fields (KGF was one of the major gold mines in India and is located in the Kolar district in Karnataka, close to the city of

Solar neutrinos

Solar neutrinos originate from the nuclear fusion powering the sun and other stars. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus The Sun (Sol is the Star at the center of the Solar System. The details of the operation of the sun are explained by the Standard Solar Model. The Standard Solar Model (SSM is the best current physical model of our Sun. In short: when four protons fuse to become one helium nucleus, two of them have to convert into neutrons, and each such conversion releases one electron neutrino. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical

The sun sends enormous numbers of neutrinos in all directions. Every second, about 70 billion (7×10¹⁰) solar neutrinos pass through every square centimeter on Earth that faces the sun. ^[12] Since neutrinos are insignificantly absorbed by the mass of the Earth, the surface area on the side of the Earth opposite the Sun receives about the same number of neutrinos as the side facing the Sun.

Supernovae

Neutrinos are an important product of Types Ib, Ic and II (core-collapse) supernovae. SN 1987A was a Supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby A supernova (plural supernovae or supernovas) is a stellar Explosion. In such events, the pressure at the core becomes so high (10¹⁴ g/cm³) that the degeneracy of electrons is not enough to prevent protons and electrons from combining to form a neutron and an electron neutrino. Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface Degenerate matter is matter which has sufficiently high Density that the dominant contribution to its Pressure rises from the Pauli Exclusion A second and more important neutrino source is the thermal energy (100 billion kelvins) of the newly formed neutron core, which is dissipated via the formation of neutrino-antineutrino pairs of all flavors. ^[13] Most of the energy produced in supernovas is thus radiated away in the form of an immense burst of neutrinos. The first experimental evidence of this phenomenon came in the year 1987, when neutrinos from supernova 1987A were detected. SN 1987A was a Supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby The water-based detectors Kamiokande II and IMB detected 11 and 8 antineutrinos of thermal origin,^[13] respectively, while the gallium-71-based Baksan detector found 5 neutrinos (lepton number = 1) of either thermal or electron-capture origin, in a burst lasting less than 13 seconds. The is a Neutrino Physics Laboratory located underground in the Mozumi Mine of the Kamioka Mining and Smelting Co IMB, the Irvine-Michigan-Brookhaven detector was a Nucleon decay experiment and Neutrino Observatory located in a salt mine on the shore of Lake Erie Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 The Baksan Neutrino Observatory ( BNO) is a Neutrino observatory of INR RAS located in the Baksan gorge in the Caucasus. In High energy physics, the lepton number is the number of Leptons minus the number of antileptons It is thought that neutrinos would also be produced from other events such as the collision of neutron stars. A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type What was particularly interesting about this event was that the neutrino signature of the supernova arrived at earth approximately 18 hours before the arrival of the first photon signature. The exceptionally weak interaction with normal matter allowed the neutrinos to pass through the churning mass of the exploding star, while the electromagnetic photons were retarded, with the photon signature of the supernova not being released until the outermost layers of the star were superheated and released a much brighter visible light signature, observed telescopically on earth some 18 hours after the neutrinos had already arrived. This point shows how weakly interacting neutrinos truly are.

Because neutrinos interact so little with matter, it is thought that a supernova's neutrino emissions carry information about the innermost regions of the explosion. Much of the visible light comes from the decay of radioactive elements produced by the supernova shock wave, and even light from the explosion itself is scattered by dense and turbulent gases. Neutrinos, on the other hand, pass through these gases, providing information about the supernova core (where the densities were large enough to influence the neutrino signal). Furthermore, the neutrino burst is expected to reach Earth before any electromagnetic waves, including visible light, gamma rays or radio waves. The exact time delay is unknown, but for a Type II supernova, astronomers expect the neutrino flood to be released seconds after the stellar core collapse, while the first electromagnetic signal may be hours or days later. The SNEWS project uses a network of neutrino detectors to monitor the sky for candidate supernova events; it is hoped that the neutrino signal will provide a useful advance warning of an exploding star. The SuperNova Early Warning System (SNEWS is a network of Neutrino detectors designed to give early warning to Astronomers in the event of a supernova

The energy of supernova neutrinos ranges from a few to several tens of MeV. However, the sites where cosmic rays are accelerated are expected to produce neutrinos that are one million times more energetic or more, produced from turbulent gasesous environments left over by supernova explosions: the supernova remnants. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on A supernova remnant ( SNR) is the structure resulting from the gigantic explosion of a Star in a Supernova. The connection between cosmic rays and supernova remnants was suggested by Walter Baade and Fritz Zwicky, shown to be consistent with the cosmic ray losses of the Milky Way if the efficiency of acceleration is about 10 percent by Ginzburg and Syrovatsky, and it is supported by a specific mechanism called "shock wave acceleration" based on Fermi ideas (which is still under development). Biography Along with Fritz Zwicky, he proposed that Supernovae could create Neutron stars He took advantage of wartime blackout conditions during Fritz Zwicky ( February 14 1898 &ndash February 8 1974) was an American-based Swiss Astronomer of Bulgarian origin The very high energy neutrinos are still to be seen, but this branch of neutrino astronomy is just in its infancy. The main existing or forthcoming experiments that aim at observing very high energy neutrinos from our galaxy are Baikal, AMANDA, [ICECUBE][1], Antares, NEMO and Nestor. The Antarctic Muon And Neutrino Detector Array ( AMANDA) is a Neutrino Telescope located beneath the Amundsen-Scott South Pole Station. Nestor Project (Nestor stands for Neutrino Extended Submarine Telescope with Oceanographic Research An international scientific collaboration whose target is the deployment of a neutrino Related information is provided by very high energy gamma ray observatories, such as HESS and MAGIC. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions HESS-dark-fulljpg|thumb|All four telescopes in operation at night]] High Energy Stereoscopic System or H MAGIC ( Major Atmospheric Gamma-ray Imaging Cherenkov Telescope) is a Gamma-ray telescope situated at the Roque de los Muchachos Observatory on La Palma Indeed, the collisions of cosmic rays are supposed to produce charged pions, whose decay give the neutrinos, but also neutral pions, whose decay give gamma rays: the environment of a supernova remnant is transparent to both types of radiation.

Still higher energy neutrinos, resulting from the interactions of extragalactic cosmic rays, could be observed with the cosmic ray observatory Auger or with the dedicated experiment named ANITA.

Cosmic background radiation

Main article: Cosmic neutrino background

It is thought that, just like the cosmic microwave background radiation left over from the Big Bang, there is a background of low energy neutrinos in our Universe. The cosmic neutrino background (CνB is the universe's background particle radiation composed of Neutrinos Like the Cosmic microwave background radiation The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. In the 1980s it was proposed that these may be the explanation for the dark matter thought to exist in the universe. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Neutrinos have one important advantage over most other dark matter candidates: we know they exist. However, they also have serious problems.

From particle experiments, it is known that neutrinos are very light. This means that they move at speeds close to the speed of light except when they have extremely low kinetic energy. Thus, dark matter made from neutrinos is termed "hot dark matter". Hot dark matter is a Hypothetical form of Dark matter which consists of particles that travel with Ultrarelativistic velocities The problem is that being fast moving, the neutrinos would tend to have spread out evenly in the universe before cosmological expansion made them cold enough to congregate in clumps. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy This would cause the part of dark matter made of neutrinos to be smeared out and unable to cause the large galactic structures that we see. In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter

Further, these same galaxies and groups of galaxies appear to be surrounded by dark matter which is not fast enough to escape from those galaxies. Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation Presumably this matter provided the gravitational nucleus for formation. The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning the formation of the first galaxies the way This implies that neutrinos make up only a small part of the total amount of dark matter.

From cosmological arguments, relic background neutrinos are estimated to have density of 56 of each type per cubic centimeter and temperature 1. 9 K (1. 7×10^-4 eV) if they are massless, much colder if their mass exceeds 0. 001 eV. Although their density is quite high, due to extremely low neutrino cross-sections at sub-eV energies, the relic neutrino background has not yet been observed in the laboratory (e. g. boron-8 solar neutrinos -- which are emitted with a higher energy -- have been detected definitively despite having a space density that is lower than that of relic neutrinos by some 6 orders of magnitude).

Neutrino detection

Main article: Neutrino detector

Because neutrinos are very weakly interacting, neutrino detectors must be very large in order to detect a significant number of neutrinos. A neutrino detector is a device designed to detect Neutrinos Because neutrinos are very weakly interacting neutrino detectors must be very large in order to detect a significant Neutrino detectors are often built underground in order to isolate the detector from cosmic rays and other background radiation. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on

Antineutrinos were first detected in the 1950s near a nuclear reactor. Reines and Cowan used two targets containing a solution of cadmium chloride in water. Frederick Reines ( March 16 1918 – August 26 1998) was an American Physicist. Clyde Lorrain Cowan Jr ( December 6, 1919 &ndash May 24, 1974) was the co-discoverer of the Neutrino Two scintillation detectors were placed next to the cadmium targets. Antineutrino with an energy above the threshold of 1. 8 MeV caused charged current interactions with the protons in the water, producing positrons and neutrons. The resulting positron annihilations with electrons created photons with an energy of about 0. 5 MeV. Pairs of photons in coincidence could be detected by the two scintillation detectors above and below the target. The neutrons were captured by cadmium nuclei resulting in gamma rays of about 8 MeV that were detected a few microseconds after the photons from a positron annihilation event.

Since then, various detection methods have been used. Super Kamiokande is a large volume of water surrounded by photomultiplier tubes that watch for the Cherenkov radiation emitted when an incoming neutrino creates an electron or muon in the water. Super-Kamiokande, or Super-K for short is a neutrino observatory in the city of Hida, Gifu Prefecture, Japan. Photomultiplier tubes ( photomultipliers or PMT s for short members of the class of Vacuum tubes and more specifically Phototubes are extremely Čerenkov radiation (also spelled Cerenkov or Cherenkov) is Electromagnetic radiation emitted when a charged particle (such as an The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 The Sudbury Neutrino Observatory is similar, but uses heavy water as the detecting medium, which uses the same effects, but also allows the additional reaction any-flavor neutrino photo-dissociation of deuterium, resulting in a free neutron which is then detected from gamma radiation after chlorine-capture. The Sudbury Neutrino Observatory ( SNO) is a Neutrino observatory located 6800 feet (about 2 km underground in Vale Inco 's Creighton Mine Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O Other detectors have consisted of large volumes of chlorine or gallium which are periodically checked for excesses of argon or germanium, respectively, which are created by electron-neutrinos interacting with the original substance. Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 This article pertains to the chemical element For other uses see Argon (disambiguation. Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 MINOS uses a solid plastic scintillator coupled to photomultiplier tubes, while Borexino uses a liquid pseudocumene scintillator also watched by photomultiplier tubes while the proposed NOνA detector will use liquid scintillator watched by avalanche photodiodes. In Greek mythology, Minos ( Ancient Greek:) was a mythical king of Crete son of Zeus and Europa. A scintillator is a substance that absorbs high-energy (ie Ionizing) electromagnetic or charged Particle radiation then in response fluoresces Photomultiplier tubes ( photomultipliers or PMT s for short members of the class of Vacuum tubes and more specifically Phototubes are extremely A scintillator is a substance that absorbs high-energy (ie Ionizing) electromagnetic or charged Particle radiation then in response fluoresces Photomultiplier tubes ( photomultipliers or PMT s for short members of the class of Vacuum tubes and more specifically Phototubes are extremely NOνA ( NuMI Off-Axis νe Appearance is a proposed Particle physics experiment designed to detect Neutrinos in Fermilab 's NuMI (Neutrinos Avalanche photodiodes (APDs are Photodetectors that can be regarded as the semiconductor analog to Photomultipliers By applying a high reverse bias voltage (typically

Motivation for scientific interest in the neutrino

The neutrino is of scientific interest because it can make an exceptional probe for environments that are typically concealed from the standpoint of other observation techniques, such as optical and radio observation.

The first such use of neutrinos was proposed in the early 20th century for observation of the core of the Sun. Direct optical observation of the solar core is impossible due to the diffusion of electromagnetic radiation by the huge amount of matter surrounding the core. On the other hand, neutrinos generated in stellar fusion reactions are thought to very weakly interact with matter and therefore pass right through the sun with few or no interactions. (However, the claim of an almost interaction-free passage is not backed by experimental evidence and purely theoretical so far. ) While photons emitted by the solar core may require some 40,000^[14] years to diffuse to the outer layers of the Sun, neutrinos are virtually unimpeded and cross this distance at nearly the speed of light.

Neutrinos are also useful for probing astrophysical sources beyond our solar system. Neutrinos are the only known particles that are not significantly attenuated by their travel through the interstellar medium. Optical photons can be obscured or diffused by dust, gas and background radiation. High-energy cosmic rays, in the form of fast-moving protons and atomic nuclei, are not able to travel more than about 100 megaparsecs due to the GZK cutoff. For the 1962 Bruce Conner film see Cosmic Ray (film Cosmic rays are energetic particles originating from space that impinge on History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 The Greisen-Zatsepin-Kuzmin limit ( GZK limit) is a theoretical upper limit on the energy of Cosmic rays from distant sources Neutrinos can travel this distance, and greater distances, with very little attenuation.

The galactic core of the Milky Way is completely obscured by dense gas and numerous bright objects. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply However, it is likely that neutrinos produced in the galactic core will be measurable by Earth-based neutrino telescopes in the next decade. In astronomy a neutrino telescope is usually a detector consisting of a large mass of Water or Ice, surrounded by an array of sensitive light detectors known as

The most important use of the neutrino is in the observation of supernovae, the explosions that end the lives of highly massive stars. A supernova (plural supernovae or supernovas) is a stellar Explosion. The core collapse phase of a supernova is an almost unimaginably dense and energetic event. It is so dense that no known particles are able to escape the advancing core front except for neutrinos. Consequently, supernovae are known to release approximately 99% of their energy in a rapid (10 second) burst of neutrinos. As a result, the usefulness of neutrinos as a probe for this important event in the death of a star cannot be overstated.

Determining the mass of the neutrino (see above) is also an important test of cosmology (see Dark matter). In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Many other important uses of the neutrino may be imagined in the future. It is clear that the astrophysical significance of the neutrino as an observational technique is comparable with all other known techniques, and is therefore a major focus of study in astrophysical communities.

In particle physics the main virtue of studying neutrinos is that they are typically the lowest mass, and hence lowest energy examples of particles theorized in extensions of the Standard Model of particle physics. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles For example, one would expect that if there is a fourth class of fermions beyond the electron, muon, and tau generations of particles, that a fourth generation neutrino would be the easiest to generate in a particle accelerator. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi.

Neutrinos could also be used for studying quantum gravity effects. Quantum gravity is the field of Theoretical physics attempting to unify Quantum mechanics, which describes three of the fundamental forces of nature Because they are not affected by either the strong interaction or electromagnetism, and because they are not normally found in composite particles (unlike quarks) or prone to near instantaneous decay (like many other standard model particles) it might be possible to isolate and measure gravitational effects on neutrinos at a quantum level. In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of

See also

• List of neutrino experiments
• Neutrino Factory

Notes

References

External links

• NEUTRINO UNBOUND: On-line review and e-archive on Neutrino Physics and Astrophysics
• Nova: The Ghost Particle: Documentary on US public television from WGBH
• SNEWS: Using neutrino detectors to receive early warning of supernovae
• Measuring the density of the earth's core with neutrinos
• John Bahcall Website
• Universe submerged in a sea of chilled neutrinos, New Scientist, 5 March 2008

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