EXCITED FERMION CONTRIBUTION TO Z(0) PHYSICS AT ONE-LOOP

We investigate the effects induced by excited leptons at the one-loop level in the observables measured on the Z peak at LEP. Using a genera l effective Lagrangian approach to describe the couplings of the excit ed leptons, we compute their contributions to both oblique parameters and Z partial widths. Our results show that the new effects are compar able to the present experimental sensitivity, but they do not lead to a significant improvement on the available constraints on the coupling s and masses of these states.