![]() ![]() To explain this, each neutrino flavor is assumed to be mixture of different mass eigenstates. This observation of flavor violation is also observed by man made neutrinos after propagating sizable distances. Introduction The deviation of muon-neutrino flux to electron- neutrino flux is what is known as the Atmospheric neutrino anomaly. The name originates from before the discovery in the 1970s of the heavy tau lepton, which is nearly twice the mass of a proton.1. Møller, I adopt - as a pendant to "nucleon" - the denomination "lepton" (from λεπτός, small, thin, delicate) to denote a particle of small mass. 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.Īccording to the Oxford English Dictionary, the name "lepton" (from Greek leptos meaning 'thin') was first used by physicist Léon Rosenfeld in 1948:įollowing a suggestion of Prof. two (or three) of the neutrinos are heavier than 0.008 eV.one (or more) of the neutrinos is heavier than 0.040 eV.Template:SubatomicParticle and Template:SubatomicParticle are lighter than 2.2 eV (as Template:SubatomicParticle is and the mass differences between the neutrinos are of order of millielectronvolts).Template:SubatomicParticle/ Template:SubatomicParticleĮlectron neutrino / Electron antineutrino Table of the leptons Charged lepton / antiparticle 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. The couplings of the leptons to gauge bosons are flavor-independent. 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. Conservation of the number of leptons of different flavors (for example, electron number or muon number) may sometimes be violated (as in neutrino oscillation). This principle is known as conservation of lepton number. 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. The masses of the leptons also obey a simple relation, known as the Koide formula, but at present this relationship cannot be explained. 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). 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. All six of these particles have corresponding antiparticles (such as the positron or the electron antineutrino). The other is a nearly massless neutral particle called a neutrino (such as the electron neutrino). One is a massive charged particle that bears the same name as its flavor (like the electron). Each flavor is represented by a pair of particles called a weak doublet. There are three known flavors of lepton: the electron, the muon, and the tau lepton or tau (or sometimes tauon). ![]()
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