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muon

[myoo-on] /ˈmyu ɒn/
noun, Physics.
1.
a lepton similar in most respects to the electron except that it is unstable, it may be positively charged, and its mass is approximately 207 times greater; the positively charged muon is the antiparticle of the negatively charged muon. Symbol: μ.
Origin
1950-1955
1950-55; by shortening of mu meson; see mu, -on1
Related forms
muonic, adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for muons

muon

/ˈmjuːɒn/
noun
1.
a positive or negative elementary particle with a mass 207 times that of an electron and spin 1/2. It was originally called the mu meson but is now classified as a lepton
Derived Forms
muonic (mjuːˈɒnɪk) adjective
Word Origin
C20: short for mu meson
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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muons in Science
muon
  (my'ŏn')   
An elementary particle in the lepton family having a mass 209 times that of the electron, a negative electric charge, and a mean lifetime of 2.2 × 10-6 seconds. The muon was originally called the mu-meson and was once thought to be a meson. See Table at subatomic particle.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for muons

muon

elementary subatomic particle similar to the electron but 207 times heavier. It has two forms, the negatively charged muon and its positively charged antiparticle. The muon was discovered as a constituent of cosmic-ray particle "showers" in 1936 by the American physicists Carl D. Anderson and Seth Neddermeyer. Because of its mass, it was at first thought to be the particle predicted by the Japanese physicist Yukawa Hideki in 1935 to explain the strong force that binds protons and neutrons together in atomic nuclei. It was subsequently discovered, however, that a muon is correctly assigned as a member of the lepton group of subatomic particles-i.e., it never reacts with nuclei or other particles through the strong interaction. A muon is relatively unstable, with a lifetime of only 2.2 microseconds before it decays by the weak force into an electron and two kinds of neutrinos. Because muons are charged, before decaying they lose energy by displacing electrons from atoms (ionization). At high-particle velocities close to the speed of light, ionization dissipates energy in relatively small amounts, so muons in cosmic radiation are extremely penetrating and can travel thousands of metres below the Earth's surface

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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