Renormalization and ultraviolet sensitivity of gauge vertices in universal extra dimensions

TL;DR

This paper investigates how radiative corrections and UV cutoff effects influence gauge couplings in models with universal extra dimensions, finding that UV sensitivity is generally small and manageable for phenomenology.

Contribution

It provides a detailed analysis of the UV sensitivity of gauge vertices in MUED, combining functional flow equations and explicit diagrammatic calculations.

Findings

UV sensitivity of gauge vertices is relatively small

Cutoff dependence can be approximated by functional flow equations

Explicit calculations show minor modifications due to compactification

Abstract

When computing radiative corrections in models with compactified extra dimen- sions, one has to sum over the entire tower of Kaluza-Klein excitations inside the loops. The loop corrections generate a difference between the coupling strength of a zero-mode gauge boson and the coupling strength of its Kaluza-Klein excitation, although both originate from the same higher-dimensional gauge interaction. Furthermore, this dis- crepancy will in general depend on the cutoff scale and assumptions about the UV completion of the extra-dimensional theory. In this article, these effects are studied in detail within the context of the minimal universal extra dimension model (MUED). The broad features of the cutoff scale dependence can be captured through the so- lution of the functional flow equation in five-dimensional space. However, an explicit diagrammatic calculation reveals some modifications due to the compactification of the extra dimension. Nevertheless, when imposing a physical renormalization condition, one finds that the UV sensitivity of the effective Kaluza-Klein gauge-boson vertex is relatively small and not very important for most phenomenological purposes. Similar conclusions should hold in a larger class of extra-dimensional models besides MUED.