Aspects of the Lepton Generation Puzzle

摘要: The existence of multiple, seemingly redundant, generations fundamental particles is one the major puzzles facing particle physicists. There are at least three lepton or flavours, as depicted in Table I, which have common a set remarkable features. These include: 1) identical electromagnetic interactions, evidenced by spectacular agreement experiments and theory on values for electron muon g-2,1 2) identical weak interactions embodied tests electronmuon universality branching ratio π→eν/π→μν, 3) absence strong interactions, 4) symmetry generation structure with quark sector required cancellation anomalies,2 5) absence flavour-changing such μ →eγ, μ− +nucleus →e− +nucleus, K→μe τ→μγ, and 6) existence conserved additive number each generation, searches neutrinoless double-beta decay.