Possible SU(4)_c × SU(3)_f × U(1) model

An anomaly-free model of strong and electroweak interactions involving leptons and quarks in the SU(4)_c × SU(3)_f × U(1) gauge theory is constructed. After spontaneous symmetry breaking, it reduces to quantum chromodynamics for strong interactions and a broken SU(3) × U(1) model for electroweak interactions. As a limiting case it gives the same results as those of the Weinberg-Salam model in the low-energy region. The Weinberg angle is bounded by sin²θ_W < 1/4 and becomes slightly less than 30° in the limiting case. Below the mass scale of SU(4)_c breaking there exists an inequality between the Weinberg angle and the strong coupling constant. which is consistent with experiments. A correction to the neutral current of the Weinberg-Salam model is suggested. A new conserved quantum number is introduced in this model and there exist several new fermions with masses lighter than 160 GeV. The Kobayashi-Maskawa expression of Cabibbo mixing for quarks may be obtained in the model, generalized to include several generations of fermions.