Spontaneously broken, local Z₂ symmetry and the anatomy of a lepton

In the framework of the gauge symmetry ${SU(2)}_{\tiny{CMB}}\times {SU(2)}_{\tiny{e}}\times {SU(2)}_{\tiny{\mu}}\times {SU(2)}_{\tiny{\tau}}$ we provide a microscopic argument why a spontaneously broken, local Z$_2$ symmetry surviving the 1$^{\tiny{st}}$ order phase transition to the confining phase of one of the SU(2) factors generates two stable spin-1/2 excitations of vastly different mass. A mixture of Fermi-Dirac and Bose-Einstein distributions with the former favored by a factor two over the latter is obtained by applying inequivalent, local-in-Euclidean-time Z$_2$ transformations to one and the same field configuration contained in the description of the center-vortex condensate.