Lepton number conservation
During all the weak and electromagnetic interactions in which the lepton participates, it is found that there is a conserved quantum number called the lepton number. The electrons e-, μ-, and τ- particles have a lepton number of +1, and the corresponding anti-particles have a lepton number of -1. For all the reaction processes, the algebraic sum of the lepton number does not change before and after the reaction, and the electron lepton number, muon lepton number, and τ lepton number also remain the same. Unlike charge conservation, charge conservation is associated with electromagnetic interactions, and lepton number conservation is not based on known interactions, but it has been experimentally found that it is always conserved.