# Neutrino of these articles concerns itself with the meaning of the term neutrino as elementary particle, further meanings of this term can over neutrino (term clarifying) be called

the neutrino is an elementary particle. It belonged to the leptons and becomes only by those Weak reciprocal effect and, as each elementary particle affects, in accordance with general relativity theory also by the gravitation. The neutrino possesses as fermion in the standard model a spin of [itex] \ hbar/2 [/itex] and negative heli coil quotation. The probability of reciprocal effect of the neutrino is extremely small. Its proofis possible and therefore difficult only over the loaded and neutral river, the Z-boson and the W-boson as exchange particles of the weak reciprocal effect. The symbol for the neutrino is the Greek letter ν.

## three neutrino generations and antineutrino

three generations of leptons are well-known, those in each case from a pair from an electrically charged particle (electron, Myon and Tauon) and an electrically neutral, associated neutrino exist. One speaks of the electron neutrino ([itex] \ nu_e< /math>), Myon neutrino ([itex] \ nu_ {\ mu}< /math>) and rope or rope on neutrino ([itex] \ nu_ {\ rope}< /math>). All leptons carry the so-called „weak charge “and spin ½. Besides it gives to each neutrinoalso an antiparticle, the antineutrino, thus an electron antineutrino ([itex] \ overline {\ nu} _e< /math>), Myon antineutrino ([itex] \ overline {\ nu} _ {\ mu}< /math>) and rope on antineutrino ([itex] \ overline {\ nu} _ {\ rope}< /math>).

The leptons differ from generation to generation only by the different masses of the electrically charged leptons during of the masses of the neutrinos so faradmits only upper borders are.

The number of kinds of neutrino with a neutrino mass, which is smaller than the mass of the Z-boson, became in precision experiments and. A. at the L3-Detektor at the CERN to exactly three determines.

There are referring to a neutrinoless doubled beta decay. This would mean that either the preservation of the lepton number hurt or the neutrino would be its own antiparticle. In the quantum-field-theoretical description this that the neutrino field would not be a Dirac - spinor, but a Majorana - spinor, would be called inContradiction to the current standard model.

The physicists Lee and Yang gave the impact for an experiment for the investigation of the spins of neutrinos and antineutrinos. This was implemented 1956 by Mrs. Wu and brought the result that parity preservation does not apply without exception.The neutrino proved as „a left-handed person “, which meant that it rotates regarding its direction of motion against the clockwise direction. Thus becomes left “and „right “possible an objective explanation of „. Within the range of the weak reciprocal effect must therefore with the transition of oneParticle to its antiparticle not only the electrical charge, but also the parity, D. h. the spin to be exchanged. The weak reciprocal effect differs thus from the electromagnetic reciprocal effect by the linkage „of the weak charge “with on the right of or left-handednessa particle. With the leptons and quarks only the left-handed particles and their right-handed antiparticles have a weak charge. On the other hand the right-handed particles and their left-handed antiparticles are neutral opposite the weak charge. Particles with weak charge can from thatVacuum emerge and again disappear. One calls this phenomenon „spontaneous (mirror) symmetry refraction “.

## neutrino and antineutrino reactions

the most well-known reaction, in which a neutrino participates, is the beta decay, into a neutron into a proton, an electronand an electron antineutrino disintegrates.

One of the two down quarks of the neutron emits the intermediate vector boson w (with beta+ the decay W+), whereby it transforms into a UP quark. The emitted W-boson disintegrates finally into an electron and an antineutrino.

The continuous spectrumthe beta decay led Wolfgang Pauli to postulate an up to then unobserved elementary particle . This particle should carry a part of the energy freed with the decay, and guarantee so the momentum conservation. Pauli called its to 4. December 1930 in a privateLetter postulated hypothetical particle first neutron; in order particles admitted to avoid a conflict with today under same name, designated Enrico Fermi it in neutrino (small neutron, “Neutrönchen”) over. Only 1933 presented its hypothesis a broader public to Pauli andstill 23 years had to then wait for the experimental proof.

Electron neutrinos develop also in large number in the sun with the fusion from hydrogen to helium for power production. The observation of the sun neutrinos in such a way specified is important, around the accurate processesto understand inside the sun and the fundamental reciprocal effects of physics.

## neutrino mass

the complete Hamilton function of the quantum self-conditions in the Glashow Salam vineyard theory contains mass terms for the neutrinos without however a reference to the size of the mass to give.Because however the experimental upper limits of the neutrino masses several orders of magnitude lie below the masses of the associated loaded leptons, it is permissible with many computations to set these to zero.

In the standard model of the elementary particles becomes during the derivation of the mass self-conditions of the fermions (Leptons and quarks) set from the quantum self-conditions the neutrino mass to zero, so that the proof of a neutrino mass requires a completion of this model. There are extensions to the today's standard model and also some interesting large ones standardized theories, which substantialNeutrinos predict.

Newest measurements prove that neutrinos actually possess (compared with the associated loaded leptons very small) a proper mass different of zero, because mass differences between the neutrino generations are a condition for the fact that them itself of a kind of neutrino into oneothers to convert can (neutrino oscillation). In the year 2002 oscillations were proven by solar neutrinos by the SNO.

For the cosmology thereby the neutrinos are a candidate for a part of the dark subject, can however if necessary the hot darkSubject place.

As the best upper limit for the electron neutrino mass at present the value of 2.2 eV, by measurement of the terminator point of the beta-ray spectrum of tritium of the Mainzer of neutrino experiment [1 ], won from the direct determination of the neutrino mass, is considered. A better upper limit expectsone itself by still precise measurements by the follow-up experiment KATRIN at the research center Karlsruhe.

To the comparison: An electron possesses a rest energy of 511 keV = 511,000 eV

also the CNGS experiment (CERN neutrino ton of Gran Sasso), its beginning for May 2006 are planned, are further clearing-up over the physics of the neutrinos to bring. At the SPS accelerator of the research center CERN with Geneva a neutrino jet is produced, which arrives then over a distance of 730 km by the interior of the earth at the Gran Sasso laboratory in Italyis and one detects there. For the production of the jet protons with an energy are shot a container helium-filled by 400 GeV at a graphite target in. The positively charged pions and Kaonen developing thereby become then by a magnetic lens system toofor a parallel jet focused and in ruins thereafter into 1 km are enough evacuated tube to Myon neutrinos and Myonen. The developing neutrinos maintain their flight direction on the Gran Sasso laboratory, while the remaining protons, pions and Kaonen caught by an iron/a graphite signbecome. The Myonenstrom, which crosses the sign exactly the same as the neutrinos, is afterwards measured, in order to determine from it the number of mailed neutrinos. Finally also the Myonen is absorbed by the rock and only the neutrinos to set their lonely journey away.Since the proper mass of the neutrinos is not equal to zero (which is considered in the meantime as proven), some the Myon neutrinos on the way into other kinds of neutrino (almost exclusively rope neutrinos) will be converted, which are to be proven then by the OPERA detector.

## neutrino astronomy

acquaintance neutrino detectors are on the one hand the radiochemical detectors (z. B. the chlorine experiment in the Homestake gold mine, the USA or the GALLEX detector in the Gran Sasso tunnel (Italy)), on the other hand the detectors which are based on the Tscherenkov principle, here above all the Sudbury neutrino Observatory (SNO) and super Kamiokande. They point solar andatmospheric neutrinos after and permit and. A. Conclusions on the neutrino mass and kind of neutrino, since admits the reactions running off in the sun inside are. Experiments such as Chooz or coming country are to be proven able over the inverse beta decay geo neutrino and reactor neutrino and supplycomplementary information from a range, which is not covered by solar neutrino detectors.

Experiments such as Amanda, Antares and Nestor have the proof of kosmogener neutrinos as a goal.

Also the neutrinos developing with supernew fact explosions can be proven and given information about thoseProcedures during supernew facts. Thus neutrinos were proven to 1987 in the Kamiokande detector eleven, which originated from the supernew facts SN1987A from the large Magellanic Cloud. These are to today the only proven neutrinos, which originate reliably from supernew facts.

## History

Wolfgang Pauli postulated 1930 for the first time the neutrino, since otherwise (for a two-body decay) the spectrum of the beta decay could not be explained. The postulate took place in a letter to the participants of a conference in Tübingen, beginning with the words „loveRadioactive ladies and gentlemen “, in which it asked the question about a possible experimental proof. The experimental proof of the neutrino succeeded however only 1956 by Clyde L. Cowan and Frederick pure on the basis the inverse beta decay ([itex] \ bar {\ nu} _e + p \ rightarrow e^ {+}+ n< /math>) at a nuclear reactor, which causes a clearly higher neutrino river than radioactive elements with the beta decay.

## Web on the left of

 Wiktionary: Neutrino - word origin, synonyms and translations