The observability of an additional discrete symmetry in the Standard Model

Standard Model may be defined with the additional discrete symmetry, i.e. with the gauge group $SU(3)\times SU(2) \times U(1)/{\cal Z}$ (${\cal Z} = Z_6$, $Z_3$ or $Z_2$) instead of the usual $SU(3)\times SU(2) \times U(1)$. It has the same perturbation expansion as the conventional one. However, it may describe nature in a different way at the energies compared to the triviality bound (of about 1 Tev). In this paper we present a possibility to observe this difference assuming that the gauge group of the Standard Model is embedded into the gauge group of an {\it a priory} unknown model, which describes physics at a Tev scale. This difference is related to the monopole content of the theory. We illustrate our results by consideration of the Petite Unification of quarks and leptons.