We study various forward-backward and polarization asymmetries evaluated near the $Z^0$ resonance for theories with SU(2${)}_{\mathrm{L}}$×U(1${)}_{\mathrm{Y}}$×U(1${)}_{\mathrm{Y}\mathcal{’}}$ and SU(2${)}_{\mathrm{L}}$×SU(2${)}_{\mathrm{R}}$×U(1${)}_{\mathrm{B}\mathrm{-}\mathrm{L}}$ gauge structures. Extension to other gauge structures is very simple in our formalism. We construct a linear combination of polarized forward-backward asymmetry and polarization asymmetry with initial-state-electron longitudinal polarization whose deviation from the value of the standard model can measure the effects of new currents directly. The analysis is exact at the tree level of the theory and enables one to study any model with any Higgs sector in terms of a fixed number of parameters. The results show that for a typical class of models the measurement of different asymmetries to 1% will impose a lower bound on $M_{Z\mathcal{’}}$, the mass of an additional neutral gauge boson, to be of order 10 $M_Z$. Even much less accurate measurements will yield interesting information about new gauge structures. We also examine the implications of extended gauge structures for the precise value of the $W^{\pm }$ mass.

• Received 27 May 1986

DOI:https://doi.org/10.1103/PhysRevD.35.51