LOOKING FOR EXTRA NEUTRAL GAUGE BOSON EFFECTS IN LONGITUDINALLY POLARIZED E+E--]W+W-

We study indirect manifestations of a heavy E6 Z' in the process e+ e- --> W+ W- with longitudinally polarized e+/- beams at energies typical of planned next-generation colliders, such as the NLC (square-root s greater-than-or-equal-to 500 GeV). We find the kinematical regions where these effects can be expected to be most pronounced, and then we assess the sensitivity of cross sections to the Z-Z' mixing angles or alternatively to the Z' mass. It results that the limits on the mixing angle could be improved to a few x 10(-4), or equivalently those for the Z' mass to approximately 10-20 TeV.