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Topic: Tau neutrino

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	Neutrino - Wikipedia, the free encyclopedia
		The first detection of actual 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.
		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.
	en.wikipedia.org /wiki/Neutrino (4274 words)

	Tau lepton - Wikipedia, the free encyclopedia
		The tau lepton belongs to the 3rd generation of leptons.
		The branching ratio for the decay of a tau into an electron and neutrinos is about 18%, and similar for decay into a muon and neutrinos.
		The tau lepton was detected through a series of experiments between 1974 and 1977 by Martin Lewis Perl with his colleagues at the SLAC-LBL group.
	en.wikipedia.org /wiki/Tauon (489 words)

	neutrino - HighBeam Encyclopedia (Site not responding. Last check: 2007-11-01)
		NEUTRINO [neutrino] [Ital.,=little neutral (particle)], elementary particle with no electric charge and a very small mass emitted during the decay of certain other particles.
		Neutrinos are also emitted when a pion decays into a muon and in the decays of a number of other elementary particles.
		Neutrinos are stable and can be absorbed only by the same weak interactions through which they are created; an energetic neutrino can induce the reverse of the decay that produced it.
	www.encyclopedia.com /doc/1E1-neutrino.html (588 words)

	Physics News Update Number 495 - Story DIRECT EVIDENCE FOR TAU NEUTRINOS (Site not responding. Last check: 2007-11-01)
		The evidence for the tau neutrino is slim but impressive: five scattering events are being exhibited at the seminar by Fermilab physicist Byron Lundberg, leader of Experiment 872, the Direct Observation of Nu Tau (or DONUT) collaboration (http://fn872.fnal.gov/).
		Evidence for a tau neutrino in the emulsion is the creation of a tau lepton, which itself quickly decays (after traveling about 1 mm) into other particles.
		The tau neutrino is the third neutrino type to be detected.
	www.aip.org /enews/physnews/2000/split/pnu495-1.htm (405 words)

	Discovery of fundamental particle concludes long-standing scientific quest (Site not responding. Last check: 2007-11-01)
		The tau neutrino leaves a track when it collides with an atomic nucleus to form a tau lepton (another fundamental particle), which leaves a short trail with a kink indicating the decay of the tau lepton.
		Scientists became alerted to the existence of the third, tau neutrino in 1977 with the discovery of the tau lepton.
		Neutrinos are known to exist in such large quantities that if they possess even a minuscule mass scientists' estimation of the overall mass of the universe would be radically altered.
	www.wsws.org /articles/2000/aug2000/neut-a14.shtml (1063 words)

	First direct observation of the tau neutrino (Site not responding. Last check: 2007-11-01)
		Pauli presented the neutrino as an explanation of the observation that the decay of the neutron produced a continuous á-spectrum.
		The characteristic signature of a tau neutrino event is the observation of a primary interaction track with a bend point or kink, identifying this track as a tau lepton.
		The principal source (~85%) of tau neutrinos and tau anti- neutrinos is the leptonic decay of the charmed meson D
	www.europhysicsnews.com /full/08/article5/article5.html (1140 words)

	SPACE.com -- Scientists Detect Elusive Subatomic Particle
		In what is being hailed as a heroic achievement in physics, scientists have found the first direct evidence of the tau neutrino, an elusive and ghostly subatomic particle that was thought to be the last missing piece in the architecture of matter.
		Neutrinos are hurtling everywhere and all the time at nearly the speed of light.
		The tau neutrino is the third and perhaps final type of neutrino to be found.
	www.space.com /scienceastronomy/astronomy/neutrino_discovery_000721.html (759 words)

	Information For the Public
		The continuing study of neutrino physics suggests that a neutrino of one family might sometimes change into a neutrino of a different family, by a mechanism known as neutrino oscillation.
		Neutrinos must have mass, and the mass cannot be identical for all three neutrino flavors.
		To determine whether neutrinos oscillate from one flavor to another, and, hence, have mass, a collaboration of 200 scientists from 26 institutions worldwide are planning the MINOS experiment.
	www-numi.fnal.gov /public/oscillations.html (888 words)

	Michael Hornish Neutrino Page
		Neutrino physics is quite unique in that it spans from nuclear and particle physics (which study the smallest objects in the universe) to astrophysics and cosmology (which study the largest objects in the universe).
		Detecting a neutrino from the sun is to detect one from a reaction that occurred about eight minutes prior, whereas light that reaches the earth from the surface of the sun in eight minutes took a million years to move from the center of the sun to the surface!
		Furthermore, while neutrino oscillations (the phenomenon of one flavor of neutrino "oscillating" into a second flavor) has been well established in recent experiments, therefore identifying a difference in the masses of the various flavors of neutrinos, determining the absolute neutrino mass values continues to be unresolved.
	www.tunl.duke.edu /~hornish/neutrino.shtml (1644 words)

	Neutrino Oscillations
		The reason is that neutrinos are produced in weak interactions, as either an electron neutrino, a muon neutrino, or a tau neutrino.
		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.
	www.ps.uci.edu /~superk/oscillation.html (1153 words)

	Howstuffworks "Final Building Block of Matter Found"
		The tau neutrino is one of the 12 subatomic particles considered to be the building blocks of all matter in the universe, according to the Standard Model.
		The tau lepton was detected through the track in the layers of emulsion it left behind, according to Vittorio Paolone, senior scientist on the project.
		The tau neutrino has been the most difficult of all subatomic particles to find because it is nearly massless, carries no electrical charge and barely interacts with surrounding matter.
	www.howstuffworks.com /news-item111.htm (397 words)

	CERN Courier - DONUT comes to neutrino town - IOP Publishing - article
		A neutrino experiment at Fermilab has seen the first direct evidence for the tau neutrino, the most elusive of the 12 particles that make up the Standard Model picture of the fundamental structure of matter.
		Although the neutrino could not be seen, energy-momentum accounting revealed "missing energy, showing that an invisible particle - the tau neutrino - had escaped in the W decays".
		Tau physics, with the tau neutrino playing an essential but invisible role, went on to become a precision science in the hands of experiments at electron-positron colliders - LEP at CERN and CESR at Cornell (January p20).
	www.cerncourier.com /main/article/40/7/2 (920 words)

	Neutrino Oscillations
		As the neutrino continues to travel, the proportion of each vary with distance, so it is said that neutrinos oscillate from one state to another.
		Neutrinos produced from the decay of pions and kaons from cosmic-ray interactions in the upper levels of the atmosphere can be measured in underground experiments.
		It is difficult to reconcile this neutrino deficit with the current understanding of the sun (standard solar model) which is extremely successful at determining other parameters (in particular, it is very successful at measuring the vibrational frequencies of solar oscillations, or sun-quakes, that can also be measured).
	www.physics.usyd.edu.au /hienergy/oscillations.html (1829 words)

	Neutrino Masses
		Neutrinos are fundamental, subatomic particles that are similar to electrons but are neutral meaning that they possess no electric charge.
		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.
		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)

	Science & Technology at Scientific American.com: Ask the Experts: Physics: What is a neutrino? (Site not responding. Last check: 2007-11-01)
		A neutrino is a subatomic particle that is very similar to an electron, but has no electrical charge and a very small mass, which might even be zero.
		Neutrinos are one of the most abundant particles in the universe.
		Supernovae too are predominantly a neutrino phenomenon, because neutrinos are the only particles that can penetrate the very dense material produced in a collapsing star; only a small fraction of the available energy is converted to light.
	www.sciam.com /askexpert_question.cfm?articleID=000C732C-3B0C-1C71-84A9809EC588EF21 (583 words)

	Neutrino Astrophysics
		The reason for high-energy neutrino astronomy is to open up all wavelengths for astronomy and to peer into sources that would be opaque to photons and protons.
		Neutrinos have the penetrating power to pass through the Earth but ultra-high energy neutrinos have a sufficiently high cross-section to be used to "x-ray" the internal structure of the Earth.
		It is important and straightforward for the detector to observe a large fraction of the sky simultaneously, a key for GRB observations.
	aether.lbl.gov /www/projects/neutrino (989 words)

	taustory (Site not responding. Last check: 2007-11-01)
		Muons are the cosmic ray particles that are constantly raining down on the surface of the earth due to nuclear reactions high in the atmosphere caused by energetic particles from space.
		The third generation is made of the much rarer tau and the tau neutrino.
		This neutrino beam was directed toward the DONUT (Direct Observation of NU Tau) detector, made of layers of iron plates separated by emulsions, that is, by sheets of a sort of film for photographing tau leptons.
	quarknet.fnal.gov /run2/taustory.shtml (290 words)

	List of Publications (Site not responding. Last check: 2007-11-01)
		Measurement of the branching fraction of the radiative decay tau- ---> mu- anti-muon-neutrino tau-neutrino gamma.
		Measurement of the one prong hadronic tau branching ratios at LEP.
		Measurement of the Michel parameters in leptonic tau decays.
	lep1.tau.ac.il /elad/lp.html (1808 words)

	The Ultimate Neutrino Page
		The appearance of high energy electron neutrinos is therefore a signal of neutrino oscillation.
		As the neutrino beam does not contain any significant amount of tau neutrinos, an appearance of a charged tau lepton in a nearby detector is a signal of neutrino oscillation.
		Taus cannot be detected in normal lepton detectors, because of their short lifetime.
	cupp.oulu.fi /neutrino/nd-osc.html (544 words)

	THE TAU NEUTRINO MASS
		The tau (a heavy cousin of electrons and muons) and its associated neutrino are harder to produce and hence harder to study.
		Besides putting a limit on the tau neutrino's mass, the ARGUS group also measured its helicity; like the other neutrinos, the tau neutrino is left-handed.
		That is, the spin of the tau neutrino points in a direction opposite to its direction of motion.
	newton.ex.ac.uk /aip/glimpse.txt/physnews.50.3.html (108 words)

	Tau neutrino discovery/Dateline UC Davis/08-04-00
		Scientists have announced at Fermi National Accelerator Laboratory that they have produced the first direct evidence of the tau neutrino, confirming the existence of an extraordinarily elusive constituent of matter.
		Earlier experiments had produced only indirect evidence for the existence of the tau neutrino, which is massless or almost massless, carries no electric charge and barely interacts with surrounding matter.
		The idea for the experiment that produced the neutrino evidence came in 1994 from one of Yager’s graduate students, Vittorio Paolone, who is now on the faculty of the University of Pittsburgh, and a Fermilab physicist, Byron Lundberg.
	www.news.ucdavis.edu /dateline/080400/DL_neutrino.html (651 words)

	ScienceDaily: Physicists Find First Direct Evidence For Tau Neutrino
		Their hope was that out of one million million tau neutrinos in the beam, one would interact with an iron nucleus and produce a tau lepton, which would leave a distinctive one-millimeter signature, or track, in the emulsion.
		First Results From The Sudbury Neutrino Observatory Explain The Missing Solar Neutrinos And Reveal New Neutrino Properties (June 19, 2001) -- Physicists from Canada, the U.K. and the U.S. are announcing that their first results provide a solution to a 30-year old mystery * the puzzle of the missing solar neutrinos.
		Neutrino -- The neutrino is an elementary particle.
	www.sciencedaily.com /releases/2000/07/000725080117.htm (2114 words)

	A Neutrino Timeline
		After several years, analysis of tau decay modes leads to the conclusion that tau is accompanied by its own neutrino, nutau, which is neither nue nor numu.
		1985 The "atmospheric neutrino anomaly" is observed by IMB and Kamiokande.
		The results combined with all the earlier solar neutrino results establish the correct parameters for the solar neutrino deficit.
	kamland.stanford.edu /Timeline (754 words)

	Neutrino Astronomy
		For example, heavier neutrinos travel more slowly and by studying the structure of the neutrino wave passing by earth, we can perhaps extract the relative masses of the three types of neutrinos in a direct way, aside from that of the phenomenon of neutrino oscillations.
		The second virtue of seeking higher rather than lower energy neutrinos is that the consequences of neutrino interaction with a target (earth or detector) become more detectable as the energy release is greater.
		Neutrino detectors must be generally placed deep underground or water to escape the backgrounds caused by the inescapable rain of cosmic rays upon the atmosphere.
	www.phys.hawaii.edu /~jgl/nuastron.html (2813 words)

	Theory: Leptons
		The only known difference between the three neutrino types is which type of the charged lepton they are associated with during production or decay processes.
		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).
		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)

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