A note on gauge-fixing in the electroweak sector of nmUED

TL;DR

This paper investigates gauge-fixing in a five-dimensional Universal Extra-Dimensional model with boundary localized terms, analyzing how these terms affect the electroweak sector, KK spectra, and symmetry-breaking scalars.

Contribution

It provides a detailed calculation of the gauge-fixing mechanism in a non-minimal UED model with boundary terms, highlighting differences from minimal UED.

Findings

Modified KK spectra due to boundary localized terms

Different compositions and masses of Goldstone and physical scalars

Gauge-fixing choices influence scalar sector in non-minimal UED

Abstract

Electroweak observables are highly sensitive to the loop corrections. Therefore, a proper gauge-fixing mechanism is always needed to define the propagators which are involved in Feynman loop amplitude. With this spirit we compute gauge-fixing mechanism in five dimensional (5-D) Universal Extra-Dimensional (UED) model with boundary localised terms (BLTs). These BLTs are not 5-D operators in four-dimensional (4-D) effective theory but some sort of boundary conditions on the respective fields at the fixed points of $S^1/Z_2$ orbifold. Furthermore, these BLTs non-trivially modify the Kaluza-Klein (KK) spectra and some of the interactions among the KK-excitations compared to the minimal UED (mUED), in which, these BLTs are absent. In this note we calculate the gauge-fixing mechanism in the electroweak sector of such non-trivial UED scenario. Moreover, we discuss the composition and masses of Goldstone and any physical scalar that emerge after the symmetry breaking in this set up with different choices of gauge.