A reappraisal of constraints on Z0 models from unitarity and direct searches at the LHC

Abstract

We reexamine the ubiquitous U(1) extension of the Standard Model (SM), with a new neutral gauge boson (Z0), in a truly model-independent approach. No new fermions, except for three right-handed neutrinos, are added. We use the current LHC Drell-Yan data to put model-independent constraints on the Z0 parameter space, defined by MZ0, the Z-Z0 mixing angle (αz) and the extra U(1) effective gauge coupling (g0x), which absorb all model dependence. Additional constraints are imposed from unitarity and νµ-e scattering. However, limits extracted from direct searches turn out to be the most stringent.