Dark matter from the centre of SU(N)

TL;DR

This paper explores how the center of SU(N) gauge groups can stabilize scalar dark matter candidates, analyzing minimal models based on SU(2) and SU(3) with distinctive phenomenological implications.

Contribution

It introduces the idea that the discrete subgroup Z_N of SU(N) can ensure dark matter stability and analyzes minimal SU(2) and SU(3) models with unique symmetry breaking patterns.

Findings

SU(2) model shows interplay of two dark matter states with different masses.

SU(3) model predicts dark radiation and semi-annihilation regimes.

Distinct phenomenological signatures for each model.

Abstract

A dark sector with non-abelian gauge symmetry provides a sound framework to justify stable dark matter (DM) candidates. We consider scalar fields charged under a $SU(N)$ gauge group, and show that the centre of $SU(N)$, the discrete subgroup $Z_N$ also known as $N$-ality, can ensure the stability of scalar DM particles. We analyse in some details two minimal DM models of this class, based on $SU(2)$ and $SU(3)$, respectively. These models have non-trivial patterns of spontaneous symmetry breaking, leading to distinctive phenomenological implications. For the $SU(2)$ model these include a specific interplay of two DM states, with the same interactions but different masses, and several complementary DM annihilation regimes, either within the dark sector or through the Higgs portal. The $SU(3)$ model predicts dark radiation made of a pair of dark photons with a unique gauge coupling, as well as regimes where DM semi-annihilations become dominant and testable.