Excited fermion contribution to Z0 physics at one loop Original Research Article

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 general effective Lagrangian approach to describe the couplings of the excited leptons, we compute their contributions to both oblique parameters and Z partial widths. Our results show that the new effects are comparable to the present experimental sensitivity, but they do not lead to a significant improvement on the available constraints on the couplings and masses of these states.