Muon

In the Standard Model of particle physics, a muon (from Greek letter mu used to represent it) is a semistable fundamental particle with negative electric charge and a spin of 1/2. Together with the electron, the tauon and the neutrinos, it is classified as part of the lepton family of fermions. Like all fundamental particles, the muon has an antimatter partner of opposite charge but equal mass and spin: the antimuon.

Related Topics:
Standard Model - Particle physics - Greek - Fundamental particle - Electric charge - Spin - Electron - Tauon - Neutrino - Lepton - Fermions - Antimatter - Mass

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

For historical reasons, muons are sometimes referred to as mu mesons, even though they are not classified as mesons by modern particle physicists (see History). Muons have a mass that is 207 times the electron mass (105.6 MeV). Because of this, a muon can be thought of as an extremely heavy electron. Muons are denoted by μ- and antimuons by μ+.

Related Topics:
Mesons - History - MeV

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

On earth, muons are created when a charged pion decays. The pions are created in the upper atmosphere by cosmic radiation and have a very short decay time--a few nanoseconds. The muons created when the pion decays are also short-lived: their decay time is 2.2 microseconds. However, muons in the atmosphere are moving at very high velocities, so that the time dilation effect of special relativity make them easily detectable at the earth's surface.

Related Topics:
Pion - Cosmic radiation - Time dilation - Special relativity

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

As with the case of the other charged leptons, there is a muon-neutrino which is associated with the muon. Muon-neutrinos are denoted by νμ. Muons naturally decay into an electron, an electron-antineutrino, and a muon-neutrino.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~