The Electroweak Gauge Couplings in SO(5) × U(1) Gauge-Higgs Unification

The electroweak currents of quarks and leptons in the $SO(5) \times U(1)$ gauge-Higgs unification model in the Randall-Sundrum warped space are determined. The 4D gauge couplings deviate from those in the standard model and the weak universality is slightly violated. It is shown that the model is free from 4D anomalies and the deviations of the gauge couplings are tiny, less than 1% except for the top quark. The $Zt_L \bar t_L$, $Zt_R \bar t_R$, $Zb_L \bar b_L$ and $Zb_R \bar b_R$ couplings deviate from those in the standard model by -7%, 18%, 0.3% and 0.9% with the warp factor $z_L = 10^{15}$, respectively. The violation of the $\mu$-$e$, $\tau$-$e$ and $t$-$e$ universality in the charged current interactions is ${\cal O}(10^{-8})$, ${\cal O}(10^{-6})$ and 2.3%, respectively.