Muon
The muon is, according to the standard model of Physique of the particles, the name given to two elementary particles of positive and negative load. The muons have a Masse 207 times larger than that of the electron (105,6 MeV) and have a Spin 1/2. The muons, just like the electrons, belong to the same family of Fermion S, the Lepton S. the muons are noted μ- or μ+ according to their electric Charge.
On Ground, the muons are produced by the disintegration of pawn S charged. The pawns are created in the upper atmosphere by cosmic rays and have a weak life time (a few nanoseconds). However, the muons have a great energy, thus the effect of temporal dilation described by the restricted Relativité makes them observable on the surface Earth.
Just like for the case of the electrons, there exists a muon Neutrino which is associated with the muon. The muon neutrinos are noted by νμ.
The positive muons can form a particle called the Muonium, or μ+e-. Because of the difference in mass between the muon and the electron, the muonium resembles more a Atome of Hydrogène than the Positronium.
History
The muons were discovered by Carl David Anderson and his assistant Seth Neddermeyer, with the Caltech, in 1936, whereas they worked on the cosmic rays. They noticed particles whose trajectory curved in a way distinct from that of the electrons and other known particles, when they were subjected to a Magnetic field. These new particles carried a negative electric charge but their trajectory was less curved than that of the electrons but more curved than that of the Proton S at equal speed. It was supposed that their negative electric charge being equal to that of the electron and that being given the difference in curve of the trajectory, one was to deduce from it that they had an intermediate mass with that of electron and proton.Therefore Anderson named initially this particle mesotron , whose prefix meso- coming from the Greek means " intermédiaire". As shortly after of other particles of intermediate masses were discovered and than the generic term of meson was adopted for named such particles. Vis-a-vis the need to differentiate them, the mesotron was famous driven meson (with the Greek letter μ ( driven ) used to resemble the sound of the Latin letter m ).
However it was discovered soon that the driven meson differed significantly from other mesons; for example its decay products included/understood a Neutrino and a Antineutrino, instead of one or other, as one observed it for other mesons. Other mesons being Hadron S, which are particles formed of Quark S and thus prone to strong interactions. In the model of quark, a meson is composed of exactly two quarks (a quark and a anti-quark), unlike the Baryon S which are composed of three quarks. One discovered, however, that the driven mesons were fundamental particles (leptons) like the electrons, without structure of quark. Thus the driven mesons not being at all mesons (in the direction lately term meson defines), the term driven meson was given up and replaced by the new name of muon .
Source
Simple: Muon
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