Boundary Localized Terms in Universal Extra-Dimensional Models through a Dark Matter perspective

TL;DR

This paper investigates how boundary-localized terms in universal extra-dimensional models affect dark matter stability and relic density, revealing new parameter spaces and detection prospects for Kaluza-Klein particles as dark matter candidates.

Contribution

It demonstrates that boundary-localized terms can relax experimental bounds and restore dark matter stability, providing new insights into Kaluza-Klein dark matter phenomenology.

Findings

BLTs relax bounds on compactification scale from relic density constraints

BLT parameters are tightly correlated by dark matter measurement precision

The W_3^(1) LKP yields relic density too small at ~1 TeV mass

Abstract

In universal extra dimension (UED) models with one compactified extra dimension, a Z_2 symmetry, termed KK-parity, ensures the stability of the lightest Kaluza-Klein particle (LKP). This symmetry leads to two fixed points. In non-minimal versions of UED boundary-localised terms (BLT) for different fields are included at these fixed points and KK-parity may be violated. However, BLTs with same strength at both points induce a new Z_2 symmetry which restores the stability of the LKP. We show that the BLTs serve to relax the bounds set on the compactification scale in UED by the dark matter relic density requirement. At the same time, the precision of the dark matter measurements severely correlates the BLT parameters of gauge bosons and fermions. Depending on the parameter values, the LKP can be chosen to be the level-1 photon, which is essentially the B^(1), or the level-1 Z-boson, basically the W_3^(1). We find that in the latter case the relic density is too small for a W_3^(1) with a \sim 1 TeV mass. We also explore the prospects of direct detection of an LKP which matches the observed dark matter relic density.