Polarization to Probe an Extra Neutral Gauge Boson at e+e− Linear Collider

The sensitivity to the Z ′ couplings of the processes ee → ll, b̄b and c̄c at the linear collider with √ s = 500GeV with initial beam polarization, for typical extended model examples are studied. To this aim, the suitable integrated, polarized, observables directly related to the helicity cross sections that carry information on the individual Z ′ chiral couplings to fermions are used. We discuss the derivation of separate, model-independent limits on the couplings in the case of no observed indirect Z ′ signal within the expected experimental accuracy. In the hypothesis that such signals were, indeed, observed we assess the expected accuracy on the numerical determination of such couplings and the consequent range of Z ′ masses where the individual models can be distinguished from each other as the source of the effect. Talk given at the International School-Seminar ”The Actual Problems of Particle Physics”, Gomel, July 30 – August 8, 1999