Electroweak Interaction Model with an Undegenerate Double Symmetry
  The initial $P$-invariance of the electroweak interaction Lagrangian together with the low-energy results of the Weinberg-Salam model is provided by a local secondary symmetry. Among the transformation parameters of this symmetry there are both scalars, and pseudo-scalars with respect to the orthochronous Lorentz group. Such symmetry does admissible existence of a light (massless) axial gauge boson and its possible nonuniversal interaction with the leptons of various types. 
Leonid M. Slad