One-loop effects of Standard Model (SM) extensions comprising universal extra dimensions are essential as a consequence of Kaluza-Klein (KK) parity conservation, for they represent the very first presumable virtual effects on low-energy observables. In this paper, we calculate the one-loop $CP$-even contributions to the SM $WW\gamma$ and $WWZ$ gauge couplings produced by the KK excited modes that stand for the dynamical variables of the effective theory emerged from a generalization of the SM to five dimensions, in which the extra dimension is assumed to be universal, after compactification. The employment of a covariant gauge-fixing procedure that removes gauge invariance associated to gauge KK excited modes, while keeping electroweak gauge symmetry manifest, is a main feature of this calculation, which is performed in the Feynman-’t Hooft gauge and yields finite results that consistently decouple for a large compactification scale. After numerical evaluation, our results are comparable with the one-loop SM contributions and well within the reach of a next linear collider.

• Received 2 May 2013

DOI:https://doi.org/10.1103/PhysRevD.88.016010