Bounds on new Z bosons

Since new Z bosons (Z') are predicted by many approaches to particle physics beyond the standard model, the absence of a signal in lepton pairs at hadron colliders implies important, but very model-dependent, lower limits on Z' masses. We present an analytical procedure for converting an experimental limit on σ(Z')B(Z'→l+l-) into mass limits in a large set of models. Explicit results are given for present CERN and future Fermilab collider data. We include renormalization effects so that consideration can be restricted to grand-unification models