Electron-neutrino - Factbites

Electron-neutrino - Factbites
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Topic: Electron-neutrino

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	What's a Neutrino?
		Hence, the "electron neutrino" is associated with the electron, and two other neutrinos are associated with heavier versions of the electron called the muon and the tau (elementary particles are frequently labelled with Greek letters, to confuse the layman).
		It is soon recognized to be a heavier version of the electron and muon, and its decay exhibits the same apparent imbalance of energy and momentum that led Pauli to predict the existence of the neutrino in 1931.
		This is the origin of the long-standing "solar neutrino problem." The possibility that the missing electron neutrinos may have transformed into another type (undetectable to this experiment) is soon suggested, but unreliability of the solar model on which the expected neutrino rates are based is initially considered a more likely explanation.
	www.ps.uci.edu /~superk/neutrino.html (946 words)

	neutrino on Encyclopedia.com
		In 1962 it was found that the neutrino associated with the muon (the muon neutrino) is distinct from that associated with the electron (the electron neutrino).
		Like the electron, the neutrino is a lepton ; it participates only in the weak decay of nuclear particles and has no role in the strong force binding nuclei together.
		Neutrinos are also emitted when a pion decays into a muon and in the decays of a number of other elementary particles.
	www.encyclopedia.com /html/n1/neutrino.asp (969 words)

	Neutrino - Wikipedia, the free encyclopedia
		This effect was first noticed due to the number of electron neutrinos detected from the sun's core failing to match the expected numbers, a discrepancy dubbed the "solar neutrino problem".
		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.
		The neutrino was first postulated in 1931 by Wolfgang Pauli to explain the energy spectrum of beta decays, the decay of a neutron into a proton and an electron.
	en.wikipedia.org /wiki/Electron_neutrino (3136 words)

	Neutrino mass discovered (July 1998) - Physics World - PhysicsWeb
		In this case the electron is in a mixture of spin-up and spin-down eigenstates, and it precesses around the magnetic field.
		Neutrinos would therefore represent a significant amount of "dark matter", mass that we cannot see but is predicted to exist by cosmological models.
		Neutrinos were first detected in 1956 by Fred Reines of the University of California at Irvine and the late George Cowan.
	physicsweb.org /article/world/11/7/3 (1351 words)

	Solar neutrino puzzle is solved (July 2001) - Physics World - PhysicsWeb
		Electron neutrinos are produced in the Sun's core when boron-8 nuclei undergo beta decay: the Sun is not thought to produce muon or tau neutrinos.
		Two different reactions can occur when an electron neutrino strikes a deuterium nucleus: in a "neutral-current reaction" the neutrino splits the deuterium nucleus into a proton and a neutron; in a "charge-current reaction" two protons and an electron are produced.
		According to the SNO detector, the flux of electron neutrinos from the Sun is 1.75 million neutrinos per square centimetre per second.
	physicsweb.org /article/world/14/7/10 (989 words)

	Description of the neutrino
		Moreover, the neutrino seems to have a remarkable property: its spin is always oriented in the direction opposite to its velocity (it is said to be of left helicity).
		This oscillation between neutrino families could help to explain the deficit observed in the solar neutrino flux and could be a good experimental tagging of the fact that neutrinos are massive.
		The neutrinos are only concerned with the weak interaction and this allows to them to pass through the earth without any deviation or so.
	wwwlapp.in2p3.fr /neutrinos/ankes.html (761 words)

	Leptons
		Associated with the electron is a the electron neutrino.
		There are six leptons in the present structure, the electron, muon, and tau particles and their associated neutrinos.
		As one of the leptons, the electron is viewed as one of the fundamental particles.
	hyperphysics.phy-astr.gsu.edu /hbase/particles/lepton.html (635 words)

	SNO First Results
		The determination that the electron neutrinos from the Sun transform into neutrinos of another type is very important for a full understanding of the Universe at the most microscopic level.
		From this initial phase, the SNO scientists report on an accurate and specific measurement of the number of solar electron neutrinos reaching their detector, by studying a reaction unique to heavy water where a neutron is changed into a proton.
		The Sudbury Neutrino Observatory is a unique neutrino telescope, the size of a ten-storey building, 2 kilometers underground in INCO's Creighton Mine near Sudbury Ontario planned, constructed and operated by a 100-member team of scientists from Canada, the United States and the United Kingdom.
	www.sno.phy.queensu.ca /sno/first_results (1065 words)

	Atmospheric Neutrinos
		Fully contained muons and electrons are identified by a pattern recognition algorithm that uses the maximum likelihood method to compare the measured distribution of hits and with the expected shape due to a muon (sharp, collapsed angle if beta < 1) and an electron (fuzzy due to the electromagnetic shower).
		In terms of neutrino oscillations, this null result is interesting because it implies that the detailed flux calculations we rely on for the predicted zenith angle distribution properly account for the geomagnetic field.
		The pions decay to a muon and a muon neutrino.
	hep.bu.edu /~superk/atmnu (1258 words)

	Hebb, Jean (1966-08-10) Radiative corrections to neutrino-electron processes. http://resolver.caltech.edu/CaltechETD:etd-09182002-113654
		With the cut-off at the nucleon mass the charge radius of the electron neutrino is estimated to be two orders of magnitude smaller than the experimental limit.
		A characteristic distance, the neutrino charge radius, is associated with a charge distribution of the neutrino and depends on the cut-off.
		The pair annihilation corrections are used to calculate the radiative corrections to stellar neutrino luminosities in the temperature range in which the zero order process gives the dominant contribution.
	etd.caltech.edu /etd/available/etd-09182002-113654 (262 words)

	Neutrino Masses
		There are three types, or "flavors," of neutrinos, one of which is associated with the electron, one of which is associated with the muon, and one of which is associated with the tau lepton.
		Neutrinos are fundamental, subatomic particles that are similar to electrons but are neutral meaning that they possess no electric charge.
		When neutrinos are initially produced, they spin in a very specific way: If you take your left hand and point your thumb in the direction that the neutrino is moving and let your fingers curl naturally, the fingers indicate the spinning direction.
	www.jupiterscientific.org /sciinfo/numasses.html (1989 words)

	Can Gravity be Induced?
		Neutrinos have little or no charge and so cannot be significantly affected by the magnetic field of sunspots on the Sun's surface.
		The deficiency in the neutrino count may be accounted for as follows.: Neutrinos originate from, or near, the Sun's surface.
		It remains to be seen if the limit (18) to discern solar neutrino origin is a technical or a natural limitation.
	www.goodfelloweb.com /nature/cgbi/index.html (3773 words)

	First Measurement of Geoneutrinos at KamLAND
		Geoneutrinos, anti-electron neutrinos emanating from the earth, are expected to serve as a unique window into the interior of our planet, revealing information that is hidden from other probes.
		Neutrinos and their anti-matter counterpart, anti-neutrinos, are subatomic particles that interact so rarely with other matter they can pass untouched through a wall of lead stretching from the earth to the moon.
		Neutrinos are produced during nuclear fusion, the reaction that lights the sun and other stars.
	www.innovations-report.com /html/reports/earth_sciences/report-47232.html (1127 words)

	The Mainz Neutrino Mass Experiment
		Up to recently neutrinos were assumed to be massless, but the actual measurements of neutrinos from the sun and of neutrinos created in the atmosphere by cosmic rays indicate that they have some probably very small mass.
		The neutrinos are 3 of the 12 fundamental particles out of which the matter is made of.
		The Mainz Neutrino Mass Experiment measures the shape of the beta decay spectrum of tritium very precisely.
	www.physik.uni-mainz.de /exakt/neutrino/en_index.html (108 words)

	The Ultimate Neutrino Page
		Majorana mass of the electron neutrino: 0.24 eV Depending on the nuclear matrix element.
		The mass of electron neutrinos is measured in tritium beta decay experiments.
		In practice the neutrinoless double beta decay is identified from the normal two neutrino double beta decay by electron spectra, which requires lots of data to be taken.
	cupp.oulu.fi /neutrino/nd-mass.html (543 words)

	Theory: Leptons
		For example, a high-energy electron-type neutrino can convert to an electron by exchanging a W-boson with a neutron (which becomes a proton when it absorbs the W boson).
		All are particles that are somewhat like electrons: they have half a quantum unit of spin angular momentum, and do not participate in strong interactions.
		If the detector detects everything but neutrinos, then an event where the total final energy detected (or the total final momentum) does not match the initial energy (or momentum) in the incoming particles, then neutrinos must have been produced.
	www2.slac.stanford.edu /vvc/theory/leptons.html (782 words)

	Neutrino Mass Measurement
		If neutrinos had no masses then all of the neutrinos coming out of the Sun would be of the electron type.
		However, SNO finds that only about 1/3 of the solar neutrinos are of the electron type and 2/3 of them are of a different type.
		Because, Process (i) is only sensitive to electron-neutrinos, while processes (ii) and (iii) are sensitive to all neutrino types, SNO is able to measure the overall flux of neutrinos emanating from the Sun and its electron-neutrino fraction.
	www.jupiterscientific.org /sciinfo/neutrinomasses.html (813 words)

	The Solar FAQ: Solar Neutrinos and Other Solar Oddities
		Neutrino travel across astronomical distances is obviously inaccessible to laboratory studies, and has for a long time been regarded as the most promising area to search for anomalies, that can explain the missing solar neutrinos.
		The energy spectrum of the neutrinos is not significantly different from expectations, though there is a hint of a surplus (or smaller deficit, rather) at the highest energies (Fukuda et al 1998e; Normile 1998a).
		Neutrino physics is in general a "hot" experimental topic today, with much work in progress, not only on neutrino oscillations, but also on other aspects of neutrino physics, as well as on neutrino astronomy.
	www.talkorigins.org /faqs/faq-solar.html (15805 words)

	Upper limit on the mass of the electron neutrino
		, of the electron neutrino from astronomical observations.
		and confirms the view that electron neutrinos do not constitute the major component of the matter density of the Universe.
		Upper limit on the mass of the electron neutrino
	www.nature.com /nature/journal/v326/n6112/abs/326476a0.html (165 words)

	PNNL Majorana Information Resources
		Recommendation: The Neutrino Scientific Assessment Group recommends that the highest priority for the first phase of a neutrino-less double beta decay program is to support research in two or more neutrino-less double beta decay experiments to explore the region of degenerate neutrino masses (& 100 meV).
		An experimental study of the neutrino mass scale implied by neutrino oscillation results is now technically within our grasp.
		The objective of the Majorana experiment is to study neutrinoless double beta decay (0νββ) with an effective Majorana-neutrino mass sensitivity below 50 meV to characterize the Majorana nature of the neutrino, the neutrino mass spectrum, and the absolute mass scale.
	majorana.pnl.gov (786 words)

	NOvA P929
		Using the NuMI Off-Axis beam to search for electron neutrino appearance.
		oscillations in the existing NuMI neutrino beam using a 30 kiloton liquid scintillator detector.
	www-nova.fnal.gov (43 words)

	Off-axis NuMI Neutrino Experiment
		Using NuMI off-axis beam to search for electron neutrino appearance
		This is an initiative to construct a new experiment utilizing the nearly existing NuMI neutrino beam.
		Work is in progress, your input and help is importnant.
	www-off-axis.fnal.gov (57 words)

	Neutrino Oscillations
		But if a neutrino with a definite mass is a mixture of both electron and muon neutrinos (this pre-condition for oscillation is termed "mixing"), what started as a pure electron neutrino with a mixture of masses has become a neutrino with a pure mass and a mixture of electron neutrino and muon neutrino properties.
		If the neutrino interacts a point where it is not in a definite state of being either an electron neutrino or a muon neutrino, which one it behaves like at that moment is anybody's guess.
		The reason is that neutrinos are produced in weak interactions, as either an electron neutrino, a muon neutrino, or a tau neutrino.
	www.ps.uci.edu /~superk/oscillation.html (57 words)

	Neutrinos
		It is soon recognized to be a heavier version of the electron and muon, and its decay exhibits the same apparent imbalance of energy and momentum that led Pauli to predict the existence of the neutrino in 1931.
		Hence, the "electron neutrino" is associated with the electron, and two other neutrinos are associated with heavier versions of the electron called the muon and the tau (elementary particles are frequently labelled with Greek letters).
		Neutrinos are affected only by a "weak" sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it.
	www.crystalinks.com /neutrinos.html (57 words)

	Neutrino Oscillations
		But if a neutrino with a definite mass is a mixture of both electron and muon neutrinos (this pre-condition for oscillation is termed "mixing"), what started as a pure electron neutrino with a mixture of masses has become a neutrino with a pure mass and a mixture of electron neutrino and muon neutrino properties.
		If the neutrino interacts a point where it is not in a definite state of being either an electron neutrino or a muon neutrino, which one it behaves like at that moment is anybody's guess.
		A rigorous mathematical explanation of neutrino oscillation is beyond the scope of this introduction, but the outlines can be sketched out for the simplified case where there are only two neutrinos involved in the process.
	www.ps.uci.edu /~superk/oscillation.html (1153 words)

	www.acadjournal.com,Vol1,Paper6
		are 4-momenta of the muon neutrino and the electron neutrino, accordingly.
		are the energies of the muon, the positron, the muon neutrino and the electron antineutrino, accordingly.
		Annihilation of a muon neutrino and an electron antineutrino into a muon and a positron in an external field
	www.acadjournal.com /2000/v1/part4/p2 (1451 words)

	Citebase - Solar Neutrinos from CNO Electron Capture
		We calculate the number of interactions in several solar neutrino detectors due to neutrinos from electron capture on 13N, 15O, and 17F, within the context of the Standard Solar Model.
		Another neutrino component that has not been widely considered is electron capture on these nuclei.
		Authors: Stonehill, L. Formaggio, J. Robertson, R. The neutrino flux from the sun is predicted to have a CNO-cycle contribution as well as the known pp-chain component.
	citebase.eprints.org /cgi-bin/citations?id=oai:arXiv.org:hep-ph/0309266 (887 words)

	Neutrinos as Dark Matter
		The electron neutrino is known to have a mass at least 50,000 times smaller than the mass of the electron, and neutrinos are often assumed to be massless - which means zero rest mass.
		The energy spectrum of the observable electrons in a radioactive beta decay is modified if the electron neutrino has a non-zero mass.
		But the neutrino background is still present today, with about 56 electron neutrinos, 56 electron anti-neutrinos, 56 muon neutrinos, etc., per cubic centimeter, for a total of 337 neutrinos per cubic centimeter in the Universe.
	www.astro.ucla.edu /~wright/neutrinos.html (887 words)

	Radioactivity
		Beta emission is accompanied by the emission of an electron antineutrino which shares the momentum and energy of the decay.
		Because either a neutrino or an antineutrino is emitted as well, there is a spectrum of energies for the electron or positron, depending upon what fraction of the reaction energy Q is carried by the massive particle.
		Positrons are emitted with the same kind of energy spectrum as electrons in negative beta decay because of the emission of the neutrino.
	hyperphysics.phy-astr.gsu.edu /hbase/nuclear/beta.html (364 words)

	neutrino on Encyclopedia.com
		In 1962 it was found that the neutrino associated with the muon (the muon neutrino) is distinct from that associated with the electron (the electron neutrino).
		Like the electron, the neutrino is a lepton ; it participates only in the weak decay of nuclear particles and has no role in the strong force binding nuclei together.
		Neutrinos are also emitted when a pion decays into a muon and in the decays of a number of other elementary particles.
	www.encyclopedia.com /html/n1/neutrino.asp (364 words)

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