Information AboutLepton |
| CATEGORIES ABOUT LEPTON | |
| leptons | |
| fundamental physics concepts | |
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In physics, a lepton is a particle with Spin 1/2 (a Fermion ) that does not experience the Strong Nuclear Force . The leptons form a family of Elementary Particles that are distinct from the other known family of fermions, the Quark s. PROPERTIES OF LEPTONS There are three known , the Muon and the Tau . Each flavor is represented by a pair of particles called a Weak Doublet . One is a massive charged particle that bears the same name as its flavor (like the Electron ). The other is a nearly massless neutral particle called a Neutrino (like the Electron Neutrino ). All six of these particles have corresponding Antiparticle s (like the Positron or the Electron Antineutrino ). 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 ). When particles interact, generally the number of leptons of the same type (electrons and electron neutrinos, muons and muon neutrinos, tau leptons and tau neutrinos) remains the same. This principle is known as conservation of Lepton Number . Conservation of the number of leptons of different flavors (for example, electron number or muon number) may sometimes be violated (as in Neutrino Oscillation ). A much stronger conservation law is the total number of leptons of all flavors, which is violated by a tiny amount in the Standard Model by the so-called Chiral Anomaly . The couplings of the leptons to Gauge Boson s are flavor-independent. This property is called ''lepton universality'' and has been tested in measurements of the tau and muon Lifetime s and of Z-boson partial decay widths, particularly at the SLC and LEP experiments. TABLE OF THE LEPTONS ETYMOLOGY According to the Oxford English Dictionary , the name "lepton" (from Greek ''leptos'') was first used by physicist Léon Rosenfeld in 1948: Following a suggestion of Prof. C. Møller, I adopt — as a pendant to "nucleon" — the denomination "lepton" (from λεπτός, small, thin, delicate) to denote a particle of small mass. The name originates from before the discovery in the 1970s of the heavy tau lepton, which is nearly twice the mass of a Proton . SEE ALSO REFERENCES EXTERNAL LINKS
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