An elementary particle in lepton family (perhaps not a meson), having a mass 209 times compared to the electron, a poor electric fee, and a mean duration of 2.2 × 10-6 seconds. Also referred to as mu-meson. See Table at subatomic particle.
An unstable primary particle into the lepton family members, having similar properties into the electron however with a mass 209 times better.
an elementary particle with a poor charge and a half-life of 2 microsecond; decays to electron and neutrino and antineutrino