Muon
A second-generation elementary charged lepton with a mass approximately 207 times greater than an electron.
Governing formula
m_μ ≈ 105.66 MeV/c², τ_μ ≈ 2.2 μs, Spin = ½
SI unit
MeV/c² (Mass Energy)
In depth
Muons (μ⁻) carry -1 e electric charge and decay via the weak force into an electron, electron antineutrino, and muon neutrino (μ⁻ → e⁻ + ν̄_e + ν_μ) with a mean lifetime of 2.2 microseconds.
Examples in the real world
Cosmic ray muons created in the upper atmosphere reaching Earth's surface due to relativistic time dilation.