Muon
The Moon's cosmic ray shadow, as seen in secondary muons generated by cosmic rays in the atmosphere, and detected 700 meters below ground, at the Soudan II detector
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| Composition | Elementary particle |
|---|---|
| Statistics | Fermionic |
| Generation | Second |
| Interactions |
Gravity, Electromagnetic, Weak |
| Symbol | μ− |
| Antiparticle | Antimuon ( μ+ ) |
| Discovered | Carl D. Anderson, Seth Neddermeyer (1936) |
| Mass | 105.6583745(24) MeV/c2 |
| Mean lifetime | 2.1969811(22)×10−6 s |
| Decays into |
e− , ν e, ν μ (most common) |
| Electric charge | −1 e |
| Color charge | None |
| Spin | 1/2 |
| Weak isospin | LH: −1/2, RH: 0 |
| Weak hypercharge | LH: -1, RH: −2 |
The muon (/ˈmjuːɒn/; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton. As is the case with other leptons, the muon is not believed to have any sub-structure—that is, it is not thought to be composed of any simpler particles.
The muon is an unstable subatomic particle with a mean lifetime of 2.2 µs, much longer than many other subatomic particles. As with the decay of the non-elementary neutron (with a lifetime around 15 minutes), muon decay is slow (by "subatomic standards") because the decay is mediated by the weak interaction exclusively (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electron of the same charge as the muon and two neutrinos of different types.
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