Comparison of discovery limits for extraZbosons at future colliders

We study and compare the discovery potential for heavy neutral gauge bosons (Z’) at various ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ and ${\mathit{pp}}^{\left(\mathrm{-}\right)}$ colliders that are planned or have been proposed. Typical discovery limits are for the Fermilab Tevatron ∼1 TeV, Di-Tevatron ∼2 TeV, CERN LHC ∼4 TeV, LSGNA (a 60 TeV pp collider) ∼13 TeV while the ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ discovery limits are 2–10× √s with the large variation reflecting the model dependence of the limits. While both types of colliders have comparable discovery limits the hadron colliders are generally less dependent on the specific Z’ model and provide more robust limits since the signal has little background. In contrast, discovery limits for ${\mathit{e}}^{+}$ ${\mathit{e}}^{\mathrm{-}}$ limits are more model dependent and, because they are based on indirect inferences of deviations from standard model predictions, they are more sensitive to systematic errors.