Electroweak precision tests for asymptotic grand unification models

A bstract Asymptotic grand unification is an alternative framework to traditional quantitative unification, as the renormalisation flow leads towards an ultra-violet safe fixed point. Phenomenologically, 5-dimensional realisations permit new particles with masses as low as the TeV scale, well below the usual unification scale. We explore the impact of such models on electroweak precision observables, focusing on a minimal SU(5) template for concreteness. We show that current precision electroweak measurements are not sensitive to this class of models, but bounds in the TeV range can be obtained by recasting LHC analyses. Future colliders, such as CEPC and FCC-ee, can push the 95% limit on the Kaluza-Klein mass beyond the direct reach of the LHC programme.