Due to a fact that the cross section in weak nuclear interactions is very little, neutrinos may pass across matter all but unhampered. For average neutrinos produced in the sun (energy of two or three MeV), it would take about a single light year (~10¹⁶m) of lead to block half of the two. Detection of neutrinos might so become challenging, requiring big detection volumes or even high intensity human-semisynthetic neutrino beams.

Types of neutrinos

There are iii known types (flavors) of neutrinos: electron neutrino ν_e, muon neutrino ν_μ and tau neutrino ν_τ, named when their partner leptons in the Standard Model (see table at perfect). A todays better mensuration of a total of neutrino types comes form researching the decompose of the Z boson. This particle might decompose into any neutrino & its antineutrino, & a additional types of neutrinos available, a shorter a lifespan of the Z boson. A latest measure put a total of lightly neutrino types (in which "light" means with mass to a lesser degree half a Z mass) at Two.984±0.008[http://pdg.lbl.gov/2004/listings/lxxx.html]. A possibility of unfertile neutrinos — neutrinos which don't participate in the weak force however which can be created across flavor oscillation (understand following) — is insensible by these Z-boson-depending mensuration. A correspondence between a six - now known - quarks in the Standard Model and a six leptons, among the two the trio neutrinos, will bring extra grounds to believe that there should exist as exactly trio types. Still, conclusive proof that there are just leash rather neutrinos remains an elusive goal of particle physics.

Flavor Oscillations
Neutrinos come universally created or even found using the swell defined flavor (negatron, negative muon, tau). But, around the phenomenon called neutrino flavor oscillation, neutrinos are entity to oscillate between a triad available flavors when it propagate across space. Specifically, this occurs because a neutrino flavor eigenstates are non eigenstates of the propagation Hamiltonian. This allow the neutrino that wwhen produced as an negatron neutrino at the given location to have the calculable probability to become found as either a mu-meson or even tau neutrino fallowing it has traveled to a second location. This burden was total one found due to a number of negatron neutrinos found from either the sun's core failing to match a potential prices, a discrepancy dubbed the "solar neutrino problem". a being of flavor cycles implies a non-zero neutrino mass, since the total of mixing between neutrino flavors is proportional to the differences in their squared-people (zero for massless neutrinos). Despite their massive nature & severity, these are however imaginable that a neutrino and antineutrino are in fact the equivalent particle, a hypothesis foremost projected per Italian physicist Ettore Majorana.

History
A neutrino was number 1 postulated within 1931 by Wolfgang Pauli to explain a energy spectrum of beta decays, the decompose of the neutron into the proton and an electron. Pauli theorized that an undetected particle was carrying away a discovered difference between a energy and angular momentum of the initial and final particles. Because of their "ghostly" properties, a 1st experimental detection of neutrinos experienced to hold off until astir Twenty-five years when it were number 1 discussed. Within 1956 Clyde Cowan, Frederick Reines, F. B. Harrison, H. W. Kruse, & The. D. McGuire published a article "Detection of the Free Neutrino: a Confirmation" in Science (see neutrino experiment), a symptom that was rewarded using a 1995 Nobel Prize.

A title neutrino was coined by Enrico Fermi - who developed a 1st theory describing neutrino interactions - as a word play in neutrone, a Italian name of the neutron. (Neutrone inside Italian means large & neutral, & neutrino means microscopic & neutral.)
Around 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. Once a third nature and severity of lepton, the tau, was discovered around 1975 at a Stanford Linear Accelerator, it too was potential to keep around an associated neutrino. Number 1 grounds to believe for this third neutrino nature & severity come from either a observation of missing energy and divergence within tau decays correspondent to the beta decompose that experienced led to the discovery of the neutrino in the 1st place. A number 1 detection of actual tau neutrino interactions was announced inside summertime of 2000 per DONUT collaboration[http://www-donut.fnal.gov/] at Fermilab, making it the latest particle of the Standard Model to have been directly found.

A difficulty inside detecting neutrinos was illustrated by Richard Feynman. He said "All you have to do is imagine something that does practically nothing. You can use your son-in-law as a prototype."

Mass

A Standard Model of particle physics assumes that neutrinos come massless, although adding massive neutrinos to the basic framework is non hard. Indeed, a through an experiment constituted phenomenon of neutrino oscillation requires non-zero neutrino masses. A strongest upper restricts in neutrino mass are from either cosmology. A Big Bang model predicts that there is a fixed ratio between a total of neutrinos & the total of photons in the cosmic microwave background. In case a sum mass of completely tierce types of neutrinos exceeded L electron volts (per neutrino), there would exist as such mass in the universe that it would collapse. This limit may be circumvented by assuming that a neutrino is unstable; nonetheless, there are restricts inside a Standard Model that produce this hard.

Neutrino sources
Human generated
Nuclear power stations are the major source of person-generated neutrinos. An typical plant will generate across $10^$ anti-neutrinos by the 2nd.

A bit of particle accelerators have been utilized to produce neutrino beams. A system is to smash protons into a fixed target, producing charged pions or kaons. These unstable particles come so magnetically focussed into an extended burrow in which it decompose patch on the wing. Because of the relativistic boost of the decaying particle the neutrinos come produced as a beam like than isotropically.

Nuclear bombs also produce super heavy many neutrinos. Fred Reines and Clyde Cowan thought about trying to detect neutrinos from either the bomb prior to it switched to wanting to find reactor neutrinos.

The Earth
Neutrinos come produced following of natural background radiation. Particularly, a decompose chains of uranium and thorium isotopes, when well as potassium-40, include beta decays which emit neutrinos.

Atmospheric neutrinos
Atmospherical neutrinos symptom from either a interaction of cosmic rays with atoms in the Earth's atmosphere, creating showers of particles, many of which are unstable and produce neutrinos when they decay.

Solar neutrinos
Solar neutrinos originate from either a nuclear fusion powering the Sun and other stars.

Raymond Davis Jr. and Masatoshi Koshiba were jointly awarded the 2002 Nobel Prize in Physics for their work in the detection of cosmic neutrinos.

Cosmological phenomena
Neutrinos come an crucial product of supernovas. Virtually all of the energy produced around supernovas is radiated away in the form of an huge burst of neutrinos, which are then produced once protons and electrons in the core combine to form neutrons. A foremost experimental grounds to believe of this phenomenon come in the season 1987, when neutrinos from either a supernova 1987a were detected. Within such cases, a densities at the core turn into and then high (10¹⁴ g/cm^Trine) that interaction between a produced neutrinos & encompassing leading matter becomes important. These are thought that neutrinos would besides become produced from either more cases like a collision of neutron stars.

Because neutrinos interact and then little by using matter, these are thought that the supernova's neutrino emissions carry trading tools all about a innermost regions of the explosion. Tremendously of the obvious weak comes from either either a decompose of radioactive elements by a supernova shock wave, & possibly weak from a explosion itself is scattered by heavy & turbulent gases. Neutrinos, then again, pass across these gases, providing info all about a supernova core (in which a densities were big plenty to influence a neutrino signal). What is more, a neutrino burst is potential to email Globe prior even to any electromagnetic waves, including obvious weak, gamma rays or radio emission. a precise period delay is unknown, however for even a Nature and severity II supernova, uranologist require a neutrino flood to become freed seconds fallowing a leading core collapse, when the foremost electromagnetic signal can be hours or times late. A [http://snews.bnl.gov SNEWS] design utilizes the network of neutrino detectors to monitor a sky for candidate supernova cases; these are hoped that the neutrino signal might provide a utile advance warning of an exploding star.

Cosmic background radiation
These are thought that a cosmic background radiation left over from either a Big Bang includes a background of moo energy neutrinos. In the 1980s it was proposed that these may be a explanation for the dark matter thought to exist in the universe. Neutrinos develop of these significant benefit across virtually all more dark matter candidates: i personally understand it survive. All the same, it besides own good problems. From either particle experiments, these are known that neutrinos tend to become hot, i personally.e. move at speeds or so a speed of light—hence this scenario was also referred to as hot dark matter. A condition is that existence hot & convenient moving, a neutrinos would tend to spread retired evenly in the universe. This would tend to drive interest become smeared out & halt a big galactic structures that we view.

Neutrino detection
Neutrinos could interact vithe a neutral todays (involving a exchange of a Z boson) or even charged todays (involving the exchange of a W boson) weak force. Around the neutral todays interaction, a neutrino leaves the detector fallowing getting transfered a few of its energy & divergence to a target particle. Whole triplet neutrino flavors may participate irrespective of the neutrino energy. Even so, there is no neutrino flavor data is left behind. Inside a charged todays interaction, the neutrino transforms into its partner lepton (negatron, mu-meson, or even tau). All a same, whenever the neutrino doesn't develop sufficient energy to produce its heavily partner's mass, a charged todays interaction is unavailable thereto. Solar & reactor neutrinos use plenty energy to produce negatron. Virtually all accelerator-depending neutrino beams potty too produce negative muon, & two or three can produce taus. the detector which could distinguish among these leptons might reveal the flavor of the incident neutrino within a charged todays interaction. Since a interaction involves a exchange of a charged boson, the target particle too changes character (e.g., neutron → proton).

Antineutrinos were foremost found inside 1953 near a nuclear reactor. Reines and Cowan used two targets containing the guide of cd chloride inside a stream. Both scintillation detectors were positioned next to the atomic number 48 targets. Antineutrino charged todays interactions using a protons in the a stream produced antielectron & neutrons. A consequent antielectron annihilations sustaining negatron created photons by having an energy of astir Cipher.Fivesome MeV. Pairs of photons within coincidence can be found per 2 scintillation detectors above & beneath a target. the neutrons were captured by atomic number 4Eighter from either decatur nuclei consequent within gamma rays of astir 8 MeV that were found two or three microseconds fallowing a photons from a antielectron annihilation event.

Cl detectors consist of the tank filled by having carbon tetrachloride. The neutrino converts the chlorine atom into one of argon via the charged todays interaction. A fluid is sporadically flushed using helium gas which would remove a ar. A he is so cooled to filtrate a atomic number 18. The atomic number 17 detector in the previous Homestake Mine near Lead, South Dakota, containing 520 short tons (470 metric tons) of fluid, made a number one measure of a deficit of negatron neutrinos from either the sun (view solar neutrino problem). The similar detector project utilizes the gallium → germanium transformation which is sensitive to lower energy neutrinos. These chemical detection methods come utile lone for even counting neutrinos; there is no neutrino counsel or energy reference is available.

"Ring-imaging" detectors require benefit of the Cherenkov light produced by charged particles moving through a medium sooner than the speed of weak in this medium. Within these detectors, the big volume of clear lesson (e.g., water system) is surrounded by weak-photosensitive photomultiplier tubes. The charged lepton produced by using sufficient energy creates Cherenkov weak which leaves the characteristic ring-such as pattern of activity on the array of photomultiplier tubes. This pattern may be utilized to infer counsel, energy, & (every now and again) flavor data all about a incident neutrino. Both a water supply-filled detectors of this nature & severity (Kamiokande and IMB) recorded the neutrino burst from either supernova 1987a. A largest such detector is the a body of water-filled Extremely-Kamiokande.

A Sudbury Neutrino Observatory (SNO) uses heavy water. Additionally to the neutrino interactions available inside the regular a river detector, the heavy hydrogen in the deuterium oxide may be broken higher by a neutrino. the resultant loose neutron is after captured, releasing a burst of gamma rays which are then found. Whole trey neutrino flavors participate equally in that dissociation reaction.

A MiniBooNE detector employs pure mineral oil as its detection medium. Mineral oil occurs as natural scintillator, so charged particles forgoing sufficient energy to make Cherenkov weak may however develop scintillation weak. This allows moo energy negative muon & protons, invisible around a stream, to become found.

Tracking calorimeters like a MINOS detectors (watch a [http://www-numi.fnal.gov NuMI-MINOS] task web page) apply alternating planes of absorber lesson & detector poop. A absorber planes provide detector mass when a detector planes provide a tracking references. Steel occurs as popular absorber selection, existence comparatively heavy & cheap & getting a benefit that it may be magnetic. A There is no$\backslash nu$the proposal suggests the utilize of fibreboard as a inexpensive way of developing a big total of less heavy mass. A active detector even is typically liquid or thin plastic scintillator, see retired by having photomultiplier tubes, although various kinda ionisation chambers use at times besides been utilized. Tracking calorimeters come exclusively utile for high energy (GeV range) neutrinos. At these energies, neutral todays interactions come out as a shower of hadronic junk & charged todays interactions come identified per presence of the charged lepton's track (even alongside a select few form of hadronic dust.) The mu-meson produced around the charged todays interaction leaves an extended penetrating track & is very simple to spot. A length of this mu-meson track & its curvature in the magnetic field provide energy & charge ($\backslash mu^+$ versus $\backslash mu^-$) reference. An negatron in a detector produces an electromagnetic shower which may be distinguished from either hadronic showers in case a coarseness of the active detector is microscopic in comparison the physical extent of the shower. Tau leptons decompose fundamentally immediately to either pi-meson or even a second charged lepton, & might't exist as found directly therein sort of detector. (To directly watch taus, 1 often looks for the kink inside tracks within photographic emulsion.)

Virtually all neutrino experiments must location a flux of cosmic rays that bombard the globe's surface. the higher energy (>50 MeV or even even and then) neutrino experiments typically handle or surround a primary detector using a "veto" detector which reveals once a cosmic ray lives into a primary detector, permitting the corresponding activity in the primary detector to exist as ignored ("vetoed"). For moo energy experiments, a cosmic rays are non directly a condition. Instead, a spallation neutrons & radioisotopes by a cosmic rays will mimic a desired physical science signals. For these experiments, a guide is to talk with a detector deep underground and then that a globe above could reduce a cosmic ray rate to adequate levels.

A few neutrino detectors come: Antarctic Muon And Neutrino Detector Array Project DUMAND Super-Kamiokande LSND MiniBooNE

Motivation for scientific interest in the neutrino
A neutrino is of scientific interest because it potty produce an exceptional probe for environments that come usually concealed from either a point of view of more observation techniques, like optical & radio observation.

A foremost such utilise of neutrinos was proposed in the early 20th century for observation of the core of the Sun. Directly optical observation of a solar core is impossible due to the diffusion of electromagnetic radiation per immense total of matter surrounding the core. Then againside, neutrinos generated in star fusion responses may be feeble interacting & so pass perfect through the sun by using couple or even there are no interactions. When photons emitted per solar core might call for 1,000 years to diffuse to a outer shells of the Sun, neutrinos come virtually unimpeded & cross this few feet away at about the speed of weak.

Neutrinos come too utile for searching astrophysical sources beyond my solar formulas. Neutrinos come a merely known particles that are non significantly attenuated by their travel through the interstellar medium. Optical photons may be obscured or even diffused by dust, flatulency & background radiation. High-energy cosmic rays, in the form of fast-moving protons & minute nuclei, are non entity to travel to a higher degree astir Hundred megaparsecs due to the GZK cutoff. Neutrinos could travel this few feet away, & greater distances, by owning super little attenuation.

A astronomical core of the Milky Way is completely obscured by heavy flatulence & many brightly objects. But, these are probably that neutrinos produced in the astronomic core is mensurable by Globe-depending neutrino scope in the next decade.

A first utilise of the neutrino is in the observation of supernovae, a explosions that prevent the lasts of extremely massive stars. the core collapse phase of a supernova is an near unthinkably heavy & gumptious event. These come then heavy that there is no known particles are take a breath to escape a forward core front except for neutrinos. Consequently, supernovae come known to release roughly 99% of their energy within the rapid (10 2nd) burst of neutrinos. Following, the utility of neutrinos as a probecome for this significant event in the demise of a star might non be overstated.

Determining a mass of the neutrino (watch above) is besides an crucial line 1 text of cosmology (look at dark matter). Numerous more crucial utilizes of the neutrino can be imagined later. These are clear that the astrophysical significance of the neutrino as an data-based system is corresponding by using everthing more known techniques, & is so a major focus of learn around astrophysical communities.

Inside particle physics a mainside virtue of researching neutrinos is that it is occasionally the last-place mass, & hence last-place energy examples of particles theorized in extensions of the standard model of particle physics. For instance, a single would require that in case there is a quaternary class of fermions beyond the negatron, mu-meson, & taon generations of particles, that the quaternary generation neutrino would exist as the easiest to generate within a particle accellerator.

Neutrinos come likewise conspicuous candidates for apply around researching quantum gravity effects. Because it is non affected by either a strong nuclear force or electromagnetism, & because these are nin unremarkably detected around composite particles (unprefer quarks) or even prone to touching instantenous decompose (like numbers of more standard exemplary particles) it is more leisurely to isolate and measure gravitative results on neutrinos at the quantum level.