Is it an experimental fact or a theoretical result to obtain the lifetime of the SM particles?

It is observed that the heavier the particle, the more unstable it is. For example: The electron m = 510 KeV, t = ∞. The muon m = 0.106 GeV, t = 2.2 10^-6 s. The tauon m = 1.78 GeV t = 2.9 10^-13...

30 October 2022 5,229 14 View