Use of Z lepton asymmetry to determine mixing between Z boson and Z' boson of E6 superstrings

We compare recent measurements of lepton asymmetries in Z decays at the CERN pp¯ collider with expectations based on mixing of the Z boson with the Z' boson in superstring-inspired E₆ electroweak models. These measurements may favor Z-Z' mixing. We compare the results with what may be learned at e⁺e^- colliders.