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# Topic: Tau lepton

###### In the News (Tue 19 Mar 19)

 Lepton - Wikipedia, the free encyclopedia The leptons form a family of elementary particles that are distinct from the other known family of fermions, the quarks. All known charged leptons have a single unit of negative or positive electric charge (depending on whether they are particles or antiparticles) and all of the neutrinos and antineutrinos have zero electric charge. The charged leptons have two possible spin states, while only one helicity is observed for the neutrinos (all the neutrinos are left-handed, and all the antineutrinos are right-handed). en.wikipedia.org /wiki/Lepton   (437 words)

 Tau lepton - Wikipedia, the free encyclopedia The tau lepton belongs to the 3rd generation of leptons. Since tau-like lepton number is conserved (only approximately, due to neutrino oscillations), a tau neutrino is created when a tau lepton decays to a muon or electron. 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   (486 words)

 Physics News Update Number 495 - Story DIRECT EVIDENCE FOR TAU NEUTRINOS While the existence of neutrinos associated with the tau lepton was not in doubt, actually observing the particle interact had not occurred until now. 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. www.aip.org /enews/physnews/2000/split/pnu495-1.htm   (405 words)

 Run to Discovery: Discovery of the Tau Neutrino   (Site not responding. Last check: 2007-11-05) Leptons are "light" particles, lacking the color charge associated with quarks and interacting via the electroweak force only. 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. This neutrino beam was directed toward he 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. pdg.lbl.gov /~lauraof/quarknet/tau.html   (307 words)

 Physics Today Online - July 2000 The two purely leptonic decay modes, in which the tau decays to an electron and two neutrinos, or to a muon and two neutrinos, should be completely understood using weak interaction theory. The frustration associated with the tau lepton comes from the disappointment of hopes that its comparatively large mass, with its concomitant large number of decay modes, would lead to a deeper understanding of the so-called Standard Model of elementary particle physics. The following eight chapters are devoted to different areas of tau physics, ranging from static properties of the tau and strong-interaction physics in tau decays, to the tau neutrino, and to searches for CP violation in tau decay. www.aip.org /pt/vol-53/iss-7/p55b.html   (667 words)

 Emily's Research Page The tau neutrino was the last of the fundamental particles predicted by the Standard Model of particle physics whose interaction had not been observed. The existence of the tau neutrino is inferred experimentally through missing energy and momentum in tau lepton decays. The decay of the tau lepton was observed in 6 candidate events. webusers.physics.umn.edu /~emaher/research/researchindex.html   (552 words)

 7th International Workshop on Tau Lepton Physics (TAU02)-Home The Seventh International Workshop on Tau Lepton Physics (TAU02) was held on the UC Santa Cruz campus from Tuesday, September 10 through Friday, September 13, 2002. At the Workshop, the full range of physics accessible through the study of the tau lepton and its neutrino was systematically explored. As with previous Tau Workshops, significant time was allowed for people to talk with each other about the physics, its implications, and how the experiments can make the most of the large data samples to be accumulated in the future. www-conf.slac.stanford.edu /tau02   (172 words)

 First direct observation of the tau neutrino The tau neutrino was postulated in 1975 after the discovery of the tau lepton by M. Perl et al. 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)

 EXN.ca | Discovery The tau neutrino was a difficult particle to find because neutrinos have little or no mass, no electric charge and barely interact with other particles around them. The tau neutrino is the third kind of neutrino known to particle physicists. Physicists were able to confirm the existence of the tau neutrino by observing the "track" or signature of a tau lepton - the particle a tau neutrino produces after it interacts with an iron nucleus - on the emulsion paper. www.exn.ca /Stories/2000/07/21/59.asp   (783 words)

 Leptons Leptons, unlike quarks, exist by themselves, and, like all particles, have a corresponding antiparticle. For example, if a tau particle decays into a lighter lepton, the tau's corresponding neutrino will be a product of the decay, keeping a total of 1 family member before and after the decay. The other products could be a lighter lepton and its corresponding ANTIneutrino, keeping a total of zero members before and after for that family of leptons. blueflag.phys.yorku.ca /yhep/leptons.html   (231 words)

 Martin Perl and the Tau Lepton The tau lepton is a superheavy cousin of the electron, the carrier of electrical current in household appliances. The two particles are identical in all respects except that the tau is more than 3,500 times heavier than the electron and survives less than a trillionth of a second, whereas the electron is stable. Addressing the question of the usefulness of the discoveries like that of the tau lepton, Perl said, "The use of the discovery of basic particles is indirect. www.osti.gov /accomplishments/perl.html   (625 words)

 Lapton - Hutchinson encyclopedia article about Lapton   (Site not responding. Last check: 2007-11-05) Any of a class of elementary particles that are not affected by the strong nuclear force. The leptons comprise the electron, muon, and tau, and their neutrinos (the electron neutrino, muon neutrino, and tau neutrino), as well as their six antiparticles. In July 2000, researchers at Fermilab, in the USA, amassed the first direct evidence for the existence of the tau lepton. encyclopedia.farlex.com /Lapton   (114 words)

 Theory: Leptons The six known types of leptons are shown in the table below. 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. 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. www2.slac.stanford.edu /vvc/theory/leptons.html   (782 words)

 Introduction   (Site not responding. Last check: 2007-11-05) Since the tau lepton itself is short-lived, its decay produced another tau-neutrino. Since the decay length of the tau lepton is about 2mm in this experiment, the tau track was recorded at least once for every tau-neutrino interaction. The kink between the tau and the lepton is reconstructed in the emulsion analysis. www.hep.umn.edu /e872/introduction.htm   (265 words)

 Physicists Detect Elusive Tau Neutrino, Ending Two-Decade Search [Free Republic]   (Site not responding. Last check: 2007-11-05) The tau neutrino is the third and perhaps final type of neutrino to be found. Hence taus and tau neutrinos carry the tau lepton number, electrons and electron neutrinos carry the electron lepton number, and muons and mu neutrinos carry the muon lepton number. But remember, the tau lepton number must be conserved in each interaction: the tau therefore also produces a tau-neutrino, and the anti-tau a tau anti-neutrino. www.freerepublic.com /forum/a39776fab182e.htm   (4243 words)

 Fermilab Confirms the Tau Neutrino 08/00   (Site not responding. Last check: 2007-11-05) The tau is the third and last neutrino to be confirmed on the Standard Model of elementary particles, a theoretical description of the basic constituents of matter and the fundamental forces of nature. Twenty-five years after discovery of the tau lepton, a collaboration of 54 physicists from the U.S., Japan, Korea, and Greece finally confirmed the direct evidence of the elusive tau neutrino working at Fermilab on the Direct Observation of the Nu Tau (DONUT) experiment. It took physicists three years of painstaking work to identify the tracks revealing a tau lepton and its decay, the key to exposing the tau neutrino's existence, before the announcement of direct evidence could be made. www.pnl.gov /energyscience/08-00/art1_new.htm   (997 words)

 [No title]   (Site not responding. Last check: 2007-11-05) To collect events with multiple taus, a new special tau trigger (the lepton plus track trigger) is installed in Run II experiment of the Collider Detector at Fermilab (CDF). The goal of the lepton plus track trigger is to collect generic dilepton (ll, l\tau, \tau\tau) events with lower p_T threshold (8GeV/c) and without prescale even at high luminosity. The Z \to \tau\tau event, where one \tau-lepton decays leptonically and the other hadronically, is a good benchmark to calibrate the lepton plus track trigger and \tau identification. www-cdf.fnal.gov /thesis/cdf7633_stop_rpv_thesis_TO.txt   (211 words)

 Martin Perl makes news in Newsday story today:   (Site not responding. Last check: 2007-11-05) In the Standard Model, the tau lepton is part of a class of lightweight particles-called leptons after the Greek word for "light"-that includes the familiar electron and a somewhat heavier cousin called the muon. For every trillion tau neutrinos that passed through the target, one would produce a tau lepton, which left a distinctive, kinked track in the emulsion about a millimeter long (or about the thickness of a paper match). But to really look for the rare incidence of a tau neutrino hitting a nucleus and transforming into a tau lepton is a hard experiment to do." The experiment involved a collaboration of 54 physicists from the United States, Japan, Korea and Greece. www.poly.edu /polypress/martinperl.cfm   (564 words)

 Dr. Nelson The tau lepton is about 3,500 times as massive as the electron but it only exists for about 1/3 of a pico-second (10-12 sec). The existence of the tau lepton, to go with the muon and the electron, has created an outstanding " e - mu - tau Puzzle ". There is, and will continue to be, a major theoretical and experimental effort to determine whether or not the Higgs-mechanism is due to a fundamental scalar elementary field or, instead, due to a macroscopic f-fbar mechanism a'la the BCS theory in superconductivity. www.binghamton.edu /physics/nelson.html   (1239 words)

 BBC News | SCI/TECH | Science finds particle perfection In the target, one out of one million, million tau neutrinos interacted with an iron nucleus and produced a tau lepton, which left its one mm tell-tale signature. They needed three years to identify it by detecting a tau lepton particle and its decay, the key to exposing the tau neutrino's secret existence. Other sub-atomic particles, such as the anti-matter counterparts of the quarks and leptons, the force-carrying particles called bosons (such as photons), and the Higgs Boson (which gives mass to some of the other particles) also appear in the Standard Model. news.bbc.co.uk /hi/english/sci/tech/newsid_843000/843163.stm   (695 words)

 First look at etau01 dataset   (Site not responding. Last check: 2007-11-05) Tau has its own ntuple, the other two have histograms and will have ntuples soon. Require, geometrically, tau does not match either electron object or muon object, especially electron, see plot. So much less possibility for [tau lepton] to be [lepton lepton], much less possibility for [tau tau] to be [tau lepton] or [lepton lepton]. www.physics.rutgers.edu /~zrwan/ditau   (248 words)

 [No title] In the process e+e- -> tau+tau-(gamma), tau+- -> X+- the effects due photon radiation, spin polarization and finite mass of the tau lepton are of similar magnitude. They should be taken into account in the analysis of the experimental data in order to subtract the trivial phenomena from the interesting ones like electroweak effects or lepton universality. The Monte Carlo simulation of the combined tau production and decay process is used to analyse the spin effects and effects of radiative corrections, including hard bremsstrahlung, simultaneously. www.cpc.cs.qub.ac.uk /summaries/AABH_v1_0.html   (265 words)

 Physicists find first direct evidence for tau neutrino 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. Paolone and his colleagues created a situation in 1997, using Fermilab's Tevatron particle accelerator, in which a beam of neutrinos was fired at a sandwich of iron plates and layers of emulsion. 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. www.eurekalert.org /pub_releases/2000-07/UoCD-Pffd-1907100.php   (836 words)

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