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Composition Elementary particle Fermion Lepton weak interaction and gravitation Antineutrino (possibly identical to the neutrino) 1930 by Wolfgang Pauli 1956 by Clyde Cowan, Frederick Reines, F. B. Harrison, H. W. Kruse, and A. D. McGuire. νe, νμ and ντ 3 - electron, muon and tau 0 0 1/2 This box: view • talk • edit

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. As of 1999, it is believed neutrinos have a minuscule, but non-zero mass. They are usually denoted by the Greek letter $nu_{}^{}$ (nu). Neutrino can be used to mean: Neutrino, a particle QNX Neutrino, an operating system Oxide & Neutrino, a rap group Neutrino (spacecraft), a suborbital spacecraft in development by Interorbital Systems Category: ... For the novel, see The Elementary Particles. ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... For the former Greek currency unit, see Greek drachma. ... A fundamental interaction or fundamental force is a mechanism by which particles interact with each other, and which cannot be explained in terms of another interaction. ... The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four fundamental interactions of nature. ... Gravity redirects here. ... Corresponding to most kinds of particle, there is an associated antiparticle with the same mass and opposite charges. ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... This article is about the Austrian-Swiss physicist. ... Clyde Lorrain Cowan Jr (1919–1974) was a captain in the United States Army Air Force. ... Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... In quantum chromodynamics (QCD), color or color charge refers to a certain property of the subatomic particles called quarks. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... For the novel, see The Elementary Particles. ... A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ... This box:      Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... For the album by Prince, see 1999 (album) 1999 is a common year starting on Friday of the Gregorian calendar, and was designated the International Year of Older Persons by the United Nations. ... For other uses, see Mass (disambiguation). ... For other uses, see Nu. ...

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. 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. Electron neutrinos or antineutrinos are generated whenever neutrons change into protons or vice versa, the two forms of beta decay. Interactions involving neutrinos are generally mediated by the weak force. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... Sol redirects here. ... Core of a small nuclear reactor used for research. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... For other senses of this term, see antimatter (disambiguation). ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... This article or section does not adequately cite its references or sources. ... For other uses, see Proton (disambiguation). ... In nuclear physics, beta decay (sometimes called neutron decay) is a type of radioactive decay in which a beta particle (an electron or a positron) is emitted. ... 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[citation needed].

Observation of a neutrino hitting a proton in a bubble chamber. The collision occurred at the point where three tracks emanate on the right of the photograph.

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. Fermi redirects here. ... For other uses, see Pun (disambiguation). ... This article or section does not adequately cite its references or sources. ...

In 1942 Kan-Chang Wang first proposed to use beta-capture to experimentally detect neutrinos.[1] In 1956 Clyde Cowan, Frederick Reines, F. 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. 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. It is now known that both the proposed and the observed particles were antineutrinos. Kan-Chang Wang (Chinese: ; Pinyin: ; Wade-Giles: Wang Kan-chang) (May 28, 1907 - December 10, 1998) is a experimental high energy physicist from China. ... Clyde Lorrain Cowan Jr (1919–1974) was a captain in the United States Army Air Force. ... Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... Science is the academic journal of the American Association for the Advancement of Science and is considered one of the worlds most prestigious scientific journals. ... Hannes AlfvÃ©n (1908â€“1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ... The neutrino experiment, also called the Cowan and Reines neutrino experiment, was performed by Clyde L. Cowan and Frederick Reines in 1956. ... This article or section does not adequately cite its references or sources. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ...

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, which earned them the 1988 Nobel Prize. 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. 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. Leon Max Lederman (born July 15, 1922 in New York) is an American experimental physicist who was awarded the Nobel Prize in Physics in 1988 for his work on neutrinos. ... Melvin Schwartz (born November 2, 1932) is an American physicist. ... Jack Steinberger (born May 25, 1921) is a physicist. ... The muon (from the letter mu (Î¼)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... Hannes AlfvÃ©n (1908â€“1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ... For the former Greek currency unit, see Greek drachma. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... The Stanford Linear Accelerator Center (SLAC) is a U.S. national laboratory operated by Stanford University for the U.S. Department of Energy. ... Schematic overview of the DONUT detector This page is for the Fermilab experiment. ... Aerial view of the Fermilab site. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... The Large Electron-Positron Collider (usually called LEP for short. ...

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. ... The solar neutrino problem was a major discrepancy between measurements of the neutrinos flowing through the Earth and theoretical models of the solar interior, lasting from the mid-1960s to about 2002. ...

The Standard Model of particle physics assumes massless neutrinos that don't change flavor. However, non-zero 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. 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 MSW effect is important to understand neutrinos emitted by the Sun, which pass through its dense atmosphere on their way to detectors on Earth. Bruno Pontecorvo Bruno Pontecorvo (Pisa, Italy 1913 - Dubna, Russia 1993) was an Italian atomic physicist, early assistant of Enrico Fermi then author of numerous studies in high energy physics, especially on neutrinos. ... In particle physics, Kaons (also called K-mesons and denoted K) are a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ... This page may meet Wikipediaâ€™s criteria for speedy deletion. ... Lincoln Wolfenstein is an American particle physicist who studies the weak interaction. ... The Mikheyev-Smirnov-Wolfenstein effect is a particle physics process which acts to enhance neutrino oscillations in matter. ...

Starting in 1998, experiments began to show that solar and atmospheric neutrinos change flavors (see Super-Kamiokande, Sudbury Neutrino Observatory). 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. Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Artists concept of SNOs detector. ...

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 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). Image:Kamland detector. ... For other uses, see Minos (disambiguation). ...

Raymond Davis Jr. and Masatoshi Koshiba were jointly awarded the 2002 Nobel Prize in Physics. 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. Raymond Davis Jr. ... Masatoshi Koshiba (å°æŸ´ æ˜Œä¿Š Koshiba Masatoshi, born on September 19, 1926 in Toyohashi, Aichi Prefecture -) is a Japanese physicist who won the Nobel Prize in Physics in 2002. ... Hannes AlfvÃ©n (1908â€“1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ... Beaded ring brightens from 2003 and 2005 SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. ... For other uses, see Supernova (disambiguation). ... Neutrino astronomy is the science of observing astronomical phenomena by detecting neutrinos, a product of thermonuclear reactions going on inside every star. ...

## Properties

The neutrino has half-integer spin ($begin{matrix}frac{1}{2}hbarend{matrix}$) and is therefore a fermion. 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 and gravity. In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... For the former Greek currency unit, see Greek drachma. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... This box:      Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ... Gravity is a force of attraction that acts between bodies that have mass. ...

Because the cross section in weak nuclear interactions is very small, neutrinos can pass through matter almost unhindered. 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. Detection of neutrinos is therefore challenging, requiring large detection volumes or high intensity artificial neutrino beams. In nuclear and particle physics, the concept of a cross section is used to express the likelihood of interaction between particles. ... The electronvolt (symbol eV) is a unit of energy. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... General Name, Symbol, Number lead, Pb, 82 Chemical series Post-transition metals or poor metals Group, Period, Block 14, 6, p Appearance bluish gray Standard atomic weight 207. ...

All neutrinos observed to date have left-handed chirality. A phenomenon is said to be chiral if it is not identical to its mirror image (see Chirality (mathematics)). The spin of a particle may be used to define a handedness for that particle. ...

### Types of neutrinos

Neutrinos in the Standard Model
of elementary particles
Fermion Symbol Mass[2]
Generation 1 (electron)
Electron neutrino $nu_e,$ < 2.2 eV
Electron antineutrino $bar{nu}_e,$ < 2.2 eV
Generation 2 (muon)
Muon neutrino $nu_mu,$ < 170 keV
Muon antineutrino $bar{nu}_mu,$ < 170 keV
Generation 3 (tau)
Tau neutrino $nu_{tau},$ < 15.5 MeV
Tau antineutrino $bar{nu}_tau,$ < 15.5 MeV

There are three known types (flavours) of neutrinos: electron neutrino νe, muon neutrino νμ and tau neutrino ντ, named after their partner leptons in 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 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.[3] 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. However, actual proof that there are only three kinds of neutrinos remains an elusive goal of particle physics. The electronvolt (symbol eV) is a unit of energy. ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... Kev can refer to either: A regional term for the chav social group in the United Kingdom An abbreviation - keV - of the unit Kiloelectronvolt An abbreviation for the given name Kevin. ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ... For other uses, see Electron (disambiguation). ... The muon (from the letter mu (Î¼)--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 a lifetime of 2. ... For the former Greek currency unit, see Greek drachma. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... In physics, the W and Z bosons are the elementary particles that mediate the weak nuclear force. ... For other uses, see Quark (disambiguation). ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...

The possibility of sterile neutrinos — relatively light neutrinos which do not participate in the weak interaction but which could be created through flavour 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. However, the currently running MiniBooNE experiment suggested, until recently, that sterile neutrinos are not required to explain the experimental data,[4] 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.[5] A sterile particle does not have any charge known to us. ... The Liquid Scintillator Neutrino Detector (LSND) was a scintillation counter at Los Alamos National Laboratory that measured the number of neutrinos being produced by a reactor. ... MiniBooNE is the first phase of the Booster Neutrino Experiment (BooNE) at Fermilab which is designed to check the results of the LSND experiment. ...

### Flavor Oscillations

Main article: Neutrino oscillation

Neutrinos are most often created or detected with a well defined flavour (electron, muon, tau). However, in a phenomenon known as neutrino flavour oscillation, neutrinos are able to oscillate between the three available flavors while they propagate through space. Specifically, this occurs because the neutrino flavor eigenstates are not the same as the neutrino mass eigenstates (simply called 1, 2, 3). 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". In the Standard Model the existence of flavor oscillations implies a non-zero neutrino mass, because the amount of mixing between neutrino flavors at a given time depends on the differences in their squared-masses (although it is not generally so, on the Standard Model mixing would be zero for massless neutrinos). In keeping with their massive nature, it is still possible that the neutrino and antineutrino are in fact the same particle, a hypothesis first proposed by the Italian physicist Ettore Majorana. The reason for the need for mass to make neutrinos equivalent to antineutrinos, is that only with a massive particle (which therefore cannot move at the speed of light) is it possible to postulate an inertial frame which moves faster than the particle, and thereby converts its spin from one type of "handedness" to the other (for example, right to left-handed spin), thus making any type of neutrino in the new frame, appear as its own antiparticle. Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ... In linear algebra, the eigenvectors (from the German eigen meaning own) of a linear operator are non-zero vectors which, when operated on by the operator, result in a scalar multiple of themselves. ... Fig. ... The solar neutrino problem was a major discrepancy between measurements of the neutrinos flowing through the Earth and theoretical models of the solar interior, lasting from the mid-1960s to about 2002. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... Ettore Majorana (Catania, Sicily, 1906 â€“ Tyrrhenian Sea, 27 March 1938 (presumed)) was an Italian physicist who began promising work on neutrino masses. ...

### 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. 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. A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ... This article is about velocity in physics. ... For other uses, see Mass (disambiguation). ... In physics, the term relativity is used in several, related contexts: Galileo first developed the principle of relativity, which is the postulate that the laws of physics are the same for all observers. ...

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-((5.1±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.[6] For other uses, see Minos (disambiguation). ...

The same observation was made, on a somewhat larger scale, with supernova 1987a. 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. 1987A supernova remnant near the center SN 1987A was a supernova in the Large Magellanic Cloud, a nearby dwarf galaxy. ...

### Mass

The Standard Model of particle physics assumes that neutrinos are massless, although adding massive neutrinos to the basic framework is not difficult. Indeed, the experimentally established phenomenon of neutrino oscillation requires neutrinos to have non-zero masses.[4] The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ...

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. 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. These indicate that the sum of the neutrino masses must be less than 0.3 electronvolt (Goobar, 2006). This article is about the physics subject. ... For other uses, see Big Bang (disambiguation). ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... CMB redirects here. ... The electronvolt (symbol eV) is a unit of energy. ... A galaxy survey is a survey of galaxies in two or three dimensions. ... In astronomical spectroscopy, the Lyman alpha forest is the sum of absorption lines seen in spectra of distant galaxies and quasars, beginning from the Lyman alpha line at 121. ...

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

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 = 0.000079 eV2 Image:Kamland detector. ...

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. The initial results indicate Δm232 = 0.003 eV2, consistent with previous results from Super-K.[7] For other uses, see Minos (disambiguation). ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ...

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.g. GERDA, CUORE/Cuoricino, NEMO 3 and others). KATRIN (Karlsruhe Tritium Neutrino Experiment) is an experiment to measure the mass of the electron neutrino with sub-eV precision by examining the spectrum of electrons emitted from the beta decay of tritium. ...

### 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 the massless limit, it means that only one of two possible chiralities is observed for either particle. These are the only chiralities included in the Standard Model of particle interactions. In particle physics, helicity is the projection of the angular momentum to the direction of motion: Because the angular momentum with respect to an axis has discrete values, helicity is discrete, too. ... This article is about momentum in physics. ... A phenomenon is said to be chiral if it is not identical to its mirror image (see Chirality (mathematics)). The spin of a particle may be used to define a handedness for that particle. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...

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. Grand unification, grand unified theory, or GUT is a theory in physics that unifies the strong interaction and electroweak interaction. ... In theoretical physics, the seesaw mechanism is a mechanism to generate very small numbers from reasonable numbers and very large 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 mν / 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).[8][9]

### Trivia

(This refers to neutrinos associated with electrons, see neutrino flavor.) For other uses, see Neutrino (disambiguation). ...

In theory, you can construct all isotopes from neutrons and neutrinos, using this method with A neutrons and B neutrinos (B<=A): For other uses, see Isotope (disambiguation). ... This article or section does not adequately cite its references or sources. ...

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

The resulting isotope would be a neutral atom (i.e. with equal number of protons and electrons). This is true because of the reaction: The mass number (A), also called atomic mass number (not to be confused with atomic number (Z) which denotes the number of protons in a nucleus) or nucleon number, is the number of nucleons (protons and neutrons) in an atomic nucleus. ... See also: List of elements by atomic number In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom. ... For other uses, see Atom (disambiguation). ...

` neutron + neutrino => proton(el. charge +) + electron(el. charge -) `

Everything else about this reaction is just a matter of energy and chance (how often it happens). For other uses, see Proton (disambiguation). ... Electric charge is a fundamental property of some subatomic particles, which determines their electromagnetic interactions. ... For other uses, see Electron (disambiguation). ... Look up chance in Wiktionary, the free dictionary. ...

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: Pyrotronic Disintegrator, 1953. ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ...

` 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. Look up trivia in Wiktionary, the free dictionary. ... This article is about the physical universe. ...

## Neutrino sources

### Artificially produced neutrinos

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. 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. Atom Smasher redirects here. ... For alternative meanings see proton (disambiguation). ... In particle physics, pion (short for the Greek pi meson = P middle) is the collective name for three subatomic particles discovered in 1947: π0, π+ and π−. Pions are the lightest mesons. ... In particle physics, Kaons (also called K-mesons and denoted K) are a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ... The Lorentz transformation (LT), named after its discoverer, the Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, which has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics. ...

Nuclear bombs also produce very large quantities of neutrinos. Fred Reines and Clyde Cowan considered the detection neutrinos from a bomb prior to their search for reactor neutrinos. The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... Clyde Lorrain Cowan Jr (1919–1974) was a captain in the United States Army Air Force. ...

### Geologically produced neutrinos

Solar neutrinos (proton-proton chain) in the Standard Solar Model

Image File history File links Download high-resolution version (1022x715, 36 KB) Summary Created by Dorottya Szam Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Neutrino Solar neutrino ... Image File history File links Download high-resolution version (1022x715, 36 KB) Summary Created by Dorottya Szam Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Neutrino Solar neutrino ... Overveiw of the proton-proton chain. ...

### 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. 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. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... Air redirects here. ... 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 Bangalore. ...

### Solar neutrinos

Solar neutrinos originate from the nuclear fusion powering the sun and other stars. The details of the operation of the sun are explained by the Standard Solar Model. 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. The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Sol redirects here. ... The Standard Solar Model (SSM) is the best current physical model of our sun. ... General Name, symbol, number helium, He, 2 Chemical series noble gases Group, period, block 18, 1, s Appearance colorless Standard atomic weight 4. ...

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.[10] 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. One thousand million (1,000,000,000) is the natural number following 999,999,999 and preceding 1,000,000,001. ...

### Supernovae

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 in our Milky Way galaxy. ...

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.

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. In the 1980s it was proposed that these may be the explanation for the dark matter thought to exist in the universe. Neutrinos have one important advantage over most other dark matter candidates: we know they exist. However, they also have serious problems. The Cosmic Neutrino Background (CNB) is the background particle radiation composed of neutrinos. ... CMB redirects here. ... For other uses, see Big Bang (disambiguation). ... For other uses, see Dark matter (disambiguation). ...

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". 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. 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. A line showing the speed of light on a scale model of Earth and the Moon, taking about 1â…“ seconds to traverse that distance. ... Hot dark matter is a form of dark matter, which consists of particles that travel with relativistic velocities. ... For other uses, see Universe (disambiguation). ... For other uses, see Dark matter (disambiguation). ... For other uses, see Galaxy (disambiguation). ...

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. Presumably this matter provided the gravitational nucleus for formation. This implies that neutrinos make up only a small part of the total amount of dark matter. The galaxies of HCG 87, about four hundred million light-years distant. ... In astrophysics, the questions of galaxy formation and evolution are: How, from a homogeneous universe, did we obtain the very heterogeneous one we live in? How did galaxies form? How do galaxies change over time? A spectacular head-on collision between two galaxies is seen in this NASA Hubble Space...

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. Neutrino detectors are often built underground in order to isolate the detector from cosmic rays and other background radiation. Until somebody writes up an article this link may prove useful : http://www. ... Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ...

Antineutrinos were first detected in 1953 near a nuclear reactor. Reines and Cowan used two targets containing a solution of cadmium chloride in water. 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. Frederick Reines Frederick Reines (March 16, 1918 - August 26, 1998) was an American physicist. ... Clyde Lorrain Cowan Jr (1919–1974) was a captain in the United States Army Air Force. ... Look up Threshold in Wiktionary, the free dictionary. ... An electronvolt (symbol: eV) is the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt. ...

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. 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. 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. 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. Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... Cherenkov radiation glowing in the core of a TRIGA reactor Cherenkov radiation (also spelled Cerenkov or sometimes ÄŒerenkov) is electromagnetic radiation emitted when a charged particle passes through an insulator at a speed greater than the speed of light in that medium. ... For other uses, see Electron (disambiguation). ... The muon (from the letter mu (Î¼)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... Artists concept of SNOs detector. ... Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... General Name, symbol, number chlorine, Cl, 17 Chemical series nonmetals Group, period, block 17, 3, p Appearance yellowish green Standard atomic weight 35. ... Not to be confused with Galium. ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Standard atomic weight 72. ... For other uses, see Minos (disambiguation). ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... NOÎ½A (NuMI Off-Axis Î½e Appearance) is a proposed particle physics experiment designed to detect neutrinos in Fermilabs NuMI beam. ... Avalanche photodiodes (APDs) are photodetectors that can be regarded as the semiconductor analog to photomultipliers. ...

## 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[12] 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. Neutrinos can travel this distance, and greater distances, with very little attenuation. Cosmic rays can loosely be defined as energetic particles originating outside of the Earth. ... The megaparsec (abbreviated Mpc) is a unit of distance used in astronomy, equal to one million parsecs. ... The Greisen-Zatsepin-Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic rays from distant sources. ...

The galactic core of the Milky Way is completely obscured by dense gas and numerous bright objects. However, it is likely that neutrinos produced in the galactic core will be measurable by Earth-based neutrino telescopes in the next decade. For other uses, see Milky Way (disambiguation). ... Neutrino astronomy is the science of observing astronomical phenomena by detecting neutrinos, a product of thermonuclear reactions going on inside every star. ...

The most important use of the neutrino is in the observation of supernovae, the explosions that end the lives of highly massive stars. 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. For other uses, see Supernova (disambiguation). ...

Determining the mass of the neutrino (see above) is also an important test of cosmology (see Dark matter). 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. For other uses, see Dark matter (disambiguation). ...

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. 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. Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ...

Neutrinos could also be used for studying quantum gravity effects. 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. Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... This box:      Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ...

The Neutrino Factory is a proposed particle accelerator complex intended to measure in detail the properties of neutrinos, extremely weakly-interacting fundamental particles that can travel in straight lines through normal matter for thousands of kilometres without interacting. ...

## Notes

1. ^ Want, Kan Chang (Jan 1942). "A Suggestion on the Detection of the Neutrino". Physical Review 61 (1-2): 97.
2. ^ Since neutrino flavor eigenstates are not the same as neutrino mass eigenstates (see neutrino oscillation), the given masses are actually mass expectation values. If the mass of a neutrino could be measured directly, the value would always be that of one of the three mass eigenstates: ν1, ν2, and ν3. In practice, the mass cannot be measured directly. Instead it is measured by looking at the shape of the endpoint of the energy spectrum in particle decays. This sort of measurement directly measures the expectation value of the mass; it is not sensitive to any of the mass eigenstates separately.
3. ^ Particle Data Group (S. Eidelman et al.) (2004). "Leptons in the 2005 Review of Particle Physics". Phys. Lett. B 592 (1): 1-5. Retrieved on 2007-11-25.
4. ^ a b Karagiorgi, G.; A. Aguilar-Arevalo, J. M. Conrad, and M. H. Shaevitz (2007). "Leptonic CP violation studies at MiniBooNE in the (3+2) sterile neutrino oscillation hypothesis". Phys Rev D 75 (013011): 1-8.
5. ^ Alpert, M. (August 2007). "Dimensional Shortcuts". Scientific American.
6. ^ Measurement of neutrino velocity with the MINOS detectors and NuMI neutrino beam, Adamson et al., arXiv:hep-ex/0706.0437
7. ^ MINOS experiment sheds light on mystery of neutrino disappearance. Fermilab (30 March 2006). Retrieved on 2007-11-25.
8. ^ B. Kayser (2005). Neutrino mass, mixing, and flavor change. Particle Data Group. Retrieved on 2007-11-25.
9. ^ Bilenky, S.M.; Giunti, C. (2001). "Lepton Numbers in the framework of Neutrino Mixing". Int. J. Mod. Phys. A 16 (3931). Retrieved on 2007-11-25.
10. ^ "Neutrino." Microsoft Encarta Online Encyclopedia, 2006
11. ^ a b Mann, Alfred K. (1997). Shadow of a star: The neutrino story of Supernova 1987A. New York: W. H. Freeman, page 122. ISBN 0716730979.
12. ^ J.N. Bahcall, Neutrino Astrophysics, Cambridge, 1989.

Physical Review is one of the oldest and most-respected scientific journals publishing research on all aspects of physics. ... In quantum mechanics, operators correspond to observable variables, eigenvectors are also called eigenstates, and the eigenvalues of an operator represent those values of the corresponding variable that have non-zero probability of occurring. ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ... In probability (and especially gambling), the expected value (or expectation) of a random variable is the sum of the probability of each possible outcome of the experiment multiplied by its payoff (value). Thus, it represents the average amount one expects to win per bet if bets with identical odds are... The Particle Data Group is an international collaboration of particle physicists that compiles and reanalyzes published results related to the properties of particles and fundamental interactions. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ... Physical Review is one of the oldest and most-respected scientific journals publishing research on all aspects of physics. ... arXiv (pronounced archive, as if the X were the Greek letter Ï‡) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... Aerial view of the Fermilab site. ... is the 89th day of the year (90th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... The Particle Data Group is an international collaboration of particle physicists that compiles and reanalyzes published results related to the properties of particles and fundamental interactions. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ... This article is about the year. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 329th day of the year (330th in leap years) in the Gregorian calendar. ...

## References

• Super-Kamiokande. Super-Kamiokande at UC Irvine. Retrieved on July 14, 2003.
• G. A. Tammann, F. K. Thielemann, D. Trautmann (2003). Opening new windows in observing the Universe (English). Europhysics News. Retrieved on 2006-06-08.
• Bahcall, John N. (1989). Neutrino Astrophysics. Cambridge University Press. ISBN 0-521-35113-8.
• Griffiths, David J. (1987). Introduction to Elementary Particles. Wiley, John & Sons, Inc. ISBN 0-471-60386-4.
• Perkins, Donald H. (1999). Introduction to High Energy Physics. Cambridge University Press. ISBN 0-521-62196-8.
• Povh, Bogdan (1995). Particles and Nuclei: An Introduction to the Physical Concepts. Springer-Verlag. ISBN 0-387-59439-6.
• Tipler, Paul; Llewellyn, Ralph (2002). Modern Physics (4th ed.). W. H. Freeman. ISBN 0-7167-4345-0.
• M. Maltoni et al. (2004). "Status of global fits to neutrino oscillations". NJP 06: 122.  arXiv:hep-ph/0405172
• R. N. Mohapatra et al. (APS neutrino theory working group) (2005). "Theory of neutrinos: a white paper". preprint.  arXiv:hep-ph/0510213
• A. Goobar, S. Hannestad, E. Mörtsell and H. Tu (2006). "A new bound on the neutrino mass from the SDSS baryon acoustic peak". JCAP 06: 019.  arXiv:astro-ph/0602155
• Neutrino Oscillations, Masses And Mixing: W.M.Alberico, Torino University&S.M. Bilenky, Dubna NRI; 2003;http://arxiv.org/PS_cache/hep-ph/pdf/0306/0306239v1.pdf

Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 159th day of the year (160th in leap years) in the Gregorian calendar. ... arXiv (pronounced archive, as if the X were the Greek letter Ï‡) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... The American Physical Society was founded in 1899 and is the worlds second largest organization of physicists. ... arXiv (pronounced archive, as if the X were the Greek letter Ï‡) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ... arXiv (pronounced archive, as if the X were the Greek letter Ï‡) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. ...

Results from FactBites:

 Neutrino oscillation - Wikipedia, the free encyclopedia (2336 words) Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. Neutrino oscillation is of theoretical and experimental interest as observation of the phenomenon implies that the neutrino has a non-zero mass, which is not part of the original Standard Model of particle physics. It is generally accepted that neutrino oscillations are due to a mismatch between the flavor and mass eigenstates of neutrinos.
 Neutrino - Wikipedia, the free encyclopedia (3985 words) A practical method for investigating neutrino masses (that is, flavour 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. 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. 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.
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