We present a novel representation of the parameter space of 𝑈 (1) extensions of the standard model.
The free parameters are the mass 𝑀 𝑍 ′ of the new neutral gauge boson 𝑍 ′ , the new gauge coupling
or equivalently the mixing angle between the standard model 𝑍 and the new 𝑍 ′ boson and finally
an appropriately chosen ration of the new 𝑈 (1) gauge charges. We use recent experimental data
to constrain these parameters in the approximate range (10 −2 , 10 4 ) GeV/𝑐 2 of 𝑍 ′ masses. The role
of the tree-level 𝜌 parameter as an indirect bound is investigated. Finally, we discuss the prospects
of 𝑍 ′ searches at future colliders. This proceedings is based on Ref. [1].