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Encyclopedia > Lepton

In physics, a lepton is a sub-atomic particle with spin of 1/2 that does not experience the strong interaction (that is, the strong nuclear force). The leptons form a family of fermions that are distinct from the other known family of fermions, the quarks. ISO 4217 Code GRD User(s) Greece Inflation 3. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... Fermions, named after Enrico Fermi, are particles which form totally-antisymmetric composite quantum states. ... For other uses, see Quark (disambiguation). ...

Contents

Properties of leptons

There are three known flavors of lepton: the electron, the muon, and the tau lepton or tau (or sometimes tauon). 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 (such as the electron neutrino). All six of these particles have corresponding antiparticles (such as 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). Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ... For other uses, see Electron (disambiguation). ... The muon (from the letter mu (μ)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... The weak isospin in theoretical physics parallels the idea of the isospin under the strong interaction, but applied under the weak interaction. ... For other uses, see Electron (disambiguation). ... For other uses, see Neutrino (disambiguation). ... The neutrino is an elementary particle. ... Corresponding to most kinds of particle, there is an associated antiparticle with the same mass and opposite charges. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... An antineutrino is the antimatter equivalent particle of the neutrino. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ... In particle physics, helicity is the projection of the angular momentum to the direction of motion: Because the angular momentum with respect to an axis has discrete values, helicity is discrete, too. ... In particle physics, helicity is the projection of the angular momentum to the direction of motion: Because the angular momentum with respect to an axis has discrete values, helicity is discrete, too. ... In particle physics, helicity is the projection of the angular momentum to the direction of motion: Because the angular momentum with respect to an axis has discrete values, helicity is discrete, too. ...


The masses of the leptons also obey a simple relation, known as the Koide formula, but at present this relationship cannot be explained. This unexplained relation was discovered by Yoshio Koide in 1981, and relates the masses of the three leptons so well that it predicted the mass of the tau lepton. ...


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. In high energy physics, the lepton number is the number of leptons minus the number of antileptons. ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... A chiral anomaly is the anomalous nonconservation of a chiral current. ...


The couplings of the leptons to gauge bosons are flavor-independent. This property is called lepton universality and has been tested in measurements of the tau and muon lifetimes and of Z-boson partial decay widths, particularly at the Stanford Linear Collider and Large Electron-Positron Collider(LEP) experiments. Gauge bosons are bosonic particles which act as carriers of the fundamental forces of Nature. ... Given an assembly of elements, the number of which decreases ultimately to zero, the lifetime (also called the mean lifetime) is a certain number that characterizes the rate of reduction (decay) of the assembly. ... The Stanford Linear Collider was a linear accelerator that collided electrons and positrons at the Stanford Linear Accelerator Center. ... The LEP tunnel at CERN, now being filled with magnets for the LHC The Large Electron-Positron Collider (LEP) is one of the largest particle accelerators finished so far. ...


Table of the leptons

Charged lepton / antiparticle Neutrino / antineutrino
Name Symbol Electric charge (e) Mass (MeV/c2) Name Symbol Electric charge (e) Mass (MeV/c2)
Electron / Positron e/e+ −1 / +1 0.511 Electron neutrino / Electron antineutrino νe/νe 0 < 0.0000022 [1]
Muon μ/μ+ −1 / +1 105.7 Muon neutrino / Muon antineutrino νμ/νμ 0 < 0.17 [1]
Tau lepton τ/τ+ −1 / +1 1777 Tau neutrino / Tau antineutrino ντ/ντ 0 < 15.5 [1]

Note that the neutrino masses are known to be non-zero because of neutrino oscillation, but their masses are sufficiently light that they have not been measured directly as of 2008. However there have been measured (indirectly based on the oscillation periods) the differences of the mass squares between the neutrinos, which have been estimated Delta m^2_{12} = 80{meV}^2 and Delta m^2_{23} approx Delta m^2_{13} = 2400{meV}^2. This leads to the following conclusions: The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ... For other uses, see Electron (disambiguation). ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... For other uses, see Electron (disambiguation). ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... For other uses, see Neutrino (disambiguation). ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... The neutrino is an elementary particle. ... An antineutrino is the antimatter equivalent particle of the neutrino. ... The muon (from the letter mu (μ)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... The muon (from the letter mu (μ)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... An antimuon is the antiparticle of the muon. ... The neutrino is an elementary particle. ... An antineutrino is the antimatter equivalent particle of the neutrino. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... An antitauon is the antiparticle of the tauon. ... The neutrino is an elementary particle. ... An antineutrino is the antimatter equivalent particle of the neutrino. ... Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvo whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. ...

  • νμ and ντ are lighter than 2.2 eV (as νe is and the mass differences between the neutrinos are of order of millielectronvolts)
  • one (or more) of the neutrinos is heavier than 0.040 eV
  • two (or three) of the neutrinos are heavier than 0.008 eV

The names "mu" and "tau" seem to have been selected due to their places in the Greek alphabet; μ is seven letters after ε, whereas τ is seven letters after μ. This page contains special characters. ...


Etymology

According to the Oxford English Dictionary, the name "lepton" (from Greek leptos meaning 'thin') was first used by physicist Léon Rosenfeld in 1948: The Oxford English Dictionary print set The Oxford English Dictionary (OED) is a dictionary published by the Oxford University Press (OUP), and is the most successful dictionary of the English language, (not to be confused with the one-volume Oxford Dictionary of English, formerly New Oxford Dictionary of English, of... Belgian physicist. ...

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.

[2]

The name originates from before the discovery in the 1970s of the heavy tau lepton, which is nearly twice the mass of a proton. For other uses, see Proton (disambiguation). ...


See also

This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ...

References

  1. ^ a b c Laboratory measurements and limits for neutrino properties.
  2. ^ Rosenfeld, Léon (1948). Nuclear Forces. Interscience Publishers, New York, xvii. 

External links

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Leptons
Look up lepton in
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  • The Particle Data Group who compile authoritative information on particle properties.
  • Leptons from the Georgia State University is a small summary of the lepton.
Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 151 languages. ... Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... For the novel, see The Elementary Particles. ... In particle physics, fermions are particles with half-integer spin, such as protons and electrons. ... For other uses, see Quark (disambiguation). ... The up quark is a first-generation quark with a charge of +(2/3)e. ... The down quark is a first-generation quark with a charge of -(1/3)e. ... The charm quark is a second-generation quark with a charge of +(2/3)e. ... The strange quark is a second-generation quark with a charge of -(1/3)e and a strangeness of −1. ... The top quark is the third-generation up-type quark with a charge of +(2/3)e. ... The bottom quark is a third-generation quark with a charge of -(1/3)e. ... For other uses, see Electron (disambiguation). ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... The muon (from the letter mu (μ)--used to represent it) is an elementary particle with negative electric charge and a spin of 1/2. ... The tau lepton (often called the tau, tau particle, or occasionally the tauon, symbol ) is a negatively charged elementary particle with a lifetime of 2. ... For other uses, see Neutrino (disambiguation). ... Antineutrinos, the antiparticles of neutrinos, are neutral particles produced in nuclear beta decay. ... In particle physics, bosons are particles with an integer spin, as opposed to fermions which have half-integer spin. ... Gauge bosons are bosonic particles which act as carriers of the fundamental forces of Nature. ... In modern physics the photon is the elementary particle responsible for electromagnetic phenomena. ... In particle physics, gluons are subatomic particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei. ... In physics, the W and Z bosons are the elementary particles that mediate the weak nuclear force. ... In physics, Faddeev-Popov ghost ci is a field that violates the spin-statistics relation. ... In physics, a bound state is a composite of two or more building blocks (particles or bodies) that behaves as a single object. ... A hadron, in particle physics, is a subatomic particle which experiences the nuclear force. ... Combinations of three u, d or s-quarks with a total spin of 3/2 form the so-called baryon decuplet. ... In particle physics, a hyperon is any subatomic particle which is a baryon (and hence a hadron and a fermion) with non-zero strangeness, but with zero charm and zero bottomness. ... In physics a nucleon is a collective name for two baryons: the neutron and the proton. ... For other uses, see Proton (disambiguation). ... This article or section does not adequately cite its references or sources. ... The Delta baryon is a relatively light 1,232 MeV/c² baryon which contains only up (u) and down (d) quarks in a combination whose total spin is 3/2 and its ground state parity is +. All varieties of Δ quickly decay via the strong force into an ordinary nucleon plus... Properties In particle physics, the omega minus (Ω−) is a type of baryon (more specifically, a hyperon). ... Mesons of spin 1 form a nonet In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... In high energy physics, a quarkonium (pl. ... In particle physics, pion (short for pi meson) is the collective name for three subatomic particles: π0, π+ and π−. Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force. ... In particle physics, Kaons (also called K-mesons and denoted K) are a group of four mesons distinguished by the fact that they carry a quantum number called strangeness. ... In particle physics, a rho meson is a short-lived hadronic particle that is an isospin triplet whose three states are denoted as , and . ... The upsilon particle () is a flavorless meson formed from a bottom quark and its antiparticle. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... For other uses, see Atom (disambiguation). ... An exotic atom is the anologue of a normal atom in which one or more of the electrons are replaced by other negative particles, such as a muon or a pion, or the positively charged nucleus is replaced by other positively charged elementary particles, or both. ... Positronium (Ps) is a system consisting of an electron and its anti-particle, a positron, bound together into an exotic atom. The orbit of the two particles and the set of energy levels is similar to that of the hydrogen atom (electron and proton). ... A muonium particle is an exotic atom made up of a positive muon and an electron, and is given the symbol Mu or μ+e–. During the muons 2 microsecond lifetime, muonium can enter into compounds such as muonium chloride (MuCl) or sodium muonide (NaMu). ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... In supersymmetry, it is proposed that every fermion should have a partner boson, known as its Superpartner. ... The axino is a hypothetical elementary particle predicted by some theories of particle physics. ... In particle physics, chargino refers to a charged superpartner, i. ... In particle physics, a gaugino is the hypothetical superpartner of a gauge boson, as predicted by gauge theory combined with supersymmetry. ... A gluino is a subatomic particle, the fermion superpartner of the gluon predicted by supersymmetry. ... The gravitino is the hypothetical supersymmetric partner of the graviton, as predicted by theories combining general relativity and supersymmetry, i. ... In particle physics, a higgsino is the hypothetical superpartner of the Higgs boson, as predicted by supersymmetry. ... In particle physics, the neutralino is a hypothetical particle and part of the doubling of the menagerie of particles predicted by supersymmetric theories. ... In particle physics, a sfermion is any of the class of spin-0 superpartners of ordinary fermions appearing in supersymmetric extensions to the Standard Model. ... The axion is an exotic subatomic particle postulated by Peccei-Quinn theory to resolve the strong-CP problem in quantum chromodynamics (QCD). ... In theoretical physics, dilaton originally referred to a theoretical scalar field; as a photon refers in one sense to the electromagnetic field. ... This article is about the hypothetical particle. ... The Higgs boson, also known as the God particle, is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. ... A tachyon (from the Greek (takhús), meaning swift, fast) is any hypothetical particle that travels at superluminal velocity. ... In particle physics, the X and Y bosons are hypothetical elementary particles analogous to the W and Z bosons, but corresponding to a new type of force, such as the forces predicted by grand unified theory. ... It has been suggested that this article or section be merged with Z boson. ... In particle physics, a Z boson (or Z-prime boson) refers to a hypothetical new neutral gauge boson (named in analogy with the Standard Model Z boson). ... A sterile particle does not have any charge known to us. ... A regular meson made from a quark (q) and antiquark (q-bar) with spins s2 and s1 respectively and having an overall angular momentum L Exotic hadrons are subatomic particles made of quarks (and possibly gluons), but which do not fit into the usual schema of hadrons. ... Ordinary baryons are bound states of 3 quarks. ... A pentaquark is a subatomic particle consisting of a group of five quarks (compared to three quarks in normal baryons and two in mesons), or more specifically four quarks and one anti-quark. ... Identities and classification of possible tetraquark mesons. ... In particle physics, a glueball is a particle containing no valence quarks. ... A tetraquark is a subatomic particle composed of four quarks. ... A mesonic molecule is a set of two or more mesons bound together by the strong force. ... In physics, a quasiparticle refers to a particle-like entity arising in certain systems of interacting particles. ... Side view of an α-helix of alanine residues in atomic detail. ... This page is about the quasiparticle. ... There is a place named Magnon (pronunciation: ma-nyon) in Gabon, see Magnon, Gabon A magnon is a collective excitation of the electrons spin structure in a crystal lattice. ... Normal modes of vibration progression through a crystal. ... In physics, the plasmon is the quasiparticle resulting from the quantization of plasma oscillations just as photons and phonons are quantizations of light and sound waves, respectively. ... This article is in need of attention. ... In solid-state physics, a polaron is formed when a moving charge (typically an electron or a hole) in a crystal with some ionic character polarizes (by its electric field) the lattice around it. ... This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... Baryon decuplet: Spin=3/2 Baryon octet: Spin=1/2 This is a list of baryons. ... A list of mesons. ... Timeline of subatomic particle discoveries. ...

  Results from FactBites:
 
Lepton - Wikipedia, the free encyclopedia (229 words)
The leptons form a family of elementary particles that are distinct from the gauge bosons and the quarks.
There are 12 known types of lepton, 3 of which are matter particles (the electron, the muon and the tauon), 3 corresponding neutrinos, and their 6 respective antiparticles.
Leptons from the Georgia State University is a small summary of the Lepton.
Lepton (currency) - Wikipedia, the free encyclopedia (135 words)
Lepton pl. Lepta (Λεπτόν pl. Λεπτά) is the name of various fractional units of currency used in the Greek-speaking world from antiquity until today.
The Roman mite was informally called lepton in the Greek-speaking parts of the Roman Empire; this use is seen in the New Testament.
In modern Greece, lepton (modern form: lepto, Λεπτό) is the name of the 1/100 denomination of all the official currencies of the Greek state: The Phoenix (1827-1832), the Drachma (1832-2001) and the Euro (2002-current).
  More results at FactBites »

 
 

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