Implications of the SO(12) gauge symmetry for grand unification

Arguments following from analyzing constraints on the currently available neutral-current data are reviewed that allow for the possible existence of a neutral boson ''lighter'' than the one encountered in the standard SU(2)/sub L/ x U(1)/sub L/+R electroweak theory. An attractive possibility of accommodating this idea of a light boson in grand unified theories is to extend the popular SO(10) gauge symmetry to SO(12) gauge symmetry. It is explicitly shown that the 32-dimensional irreducible spinor representation of the SO(12) grand unified theory accommodates the electron family, which leads to the usual left-handed currents with strength G/sub F/, and a ''twin'' electron family which leads to right-handed currents also with strength G/sub F/, leaving no room for the muon (tau) family.