Bounds on Kaluza-Klein excitations of the SM vector bosons from electroweak tests

Abstract

Within a minimal extension of the SM in 4+1 dimensions, we study how Kaluza Klein excitations of the SM gauge bosons affect the electroweak precision observables. Asymmetries in Z decays provide the dominant bound on the compactification scale M of the extra dimension. If the higgs is so light that will be discovered at LEP2, we find the following 95% CL bounds: M > 3.5 TeV (if the higgs lives in the extra dimension) and M > 4.3 TeV (if the higgs is confined to our 4 dimensions). In the second case Kaluza Klein modes give "universal"corrections and a good fit of precision data can be obtained with an heavier higgs (up to 500 GeV) and with a smaller M > 3.4 TeV.