The minimal quark-lepton symmetry model and the limit on Z′-mass

A minimal extension of the Standard Model containing the four-color quark-lepton symmetry is proposed and discussed. The existence of a rather light extra Z′-boson originating from the four-color quark-lepton symmetry is shown to be compatible with the current electroweak data. The cross section σ(e+e− → γ,Z,Z′ → ff) are calculated, and their deviations from the SM predictions are shown to be significant at s ⩽ 200 GeV and available for the measurements at the LEP200 and future colliders.