muon

noun

Etymology: Contraction of the earlier term mu-meson; the particle has now been recategorised as a lepton. Coined by Italian physicist Enrico Fermi in 1951 in his book Elementary Particles.

1. An unstable elementary particle in the lepton family, having similar properties to the electron but with a mass 207 times greater.

   “The μ-meson of Powell (called here muon) is instead a disintegration product of the pion, only weakly linked to the nucleons and therefore of little importance in the explanation of nuclear forces.”

   “The spectrum of electrons arising from the decay of the negative mu meson has been determined. The muons are arrested in the gas of a high pressure hydrogen filled diffusion cloud chamber.”