n. The negatively charged lepton that belongs to the second generation of elementary fermions and has a mass 207 times that of an electron and a mean lifetime of 2.2 × 10-6 second. Also called mu lepton. [Earlier MU MESON (from the use of the Greek letter mu, the equivalent of the Roman letter m of MESON, to distinguish it from other mesons subsequently discovered, the class of particles to which it was formerly thought to belong).] mu·onic adj. |
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