We consider the effects of $Z^0-Z^{\prime }$ mixing, where the $Z^{\prime }$ is an $E_6$ gauge boson, on processes which will be measured at $e^{+}{e}^{-}$ colliders. Using constraints from current data, we find that significant mixing may be allowed. This mixing leads to measurable changes in the $Z^0$ partial widths and $\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$. In one case, we also find that a $Z^{\prime }$ lighter than the $Z^0$ is still allowed. We discuss possibilities for its detection.

• Received 9 September 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.6