Scalar Dark Matter From Theory Space

TL;DR

The paper investigates scalar dark matter within a prototypical theory-space little Higgs model (SO(5) minimal moose) and demonstrates that exact discrete symmetries can stabilize a neutral scalar arising from the $\phi$ and $\eta$ sectors. By computing the relic density from gauge and Higgs couplings through the Boltzmann equation, it shows two viable regions: a low-mass regime around $m_{N_1} \sim 100$ GeV and a high-mass regime with $m_{N_1} \gtrsim 500$ GeV, with the allowed parameter space controlled by the mixing angle $\cos^2 \vartheta_{\eta\phi}$ and the lack of direct couplings to the $Z/\gamma$ bosons. The results indicate that a scalar WIMP DM candidate can naturally emerge in theory-space LH models with exact discrete symmetries, though the viable regions are constrained and sensitive to couplings, resonance effects, and possible beyond-the-standards-model contributions. The work highlights the interplay between electroweak symmetry breaking, discrete symmetries, and dark matter phenomenology in a UV-complete, symmetry-protected framework, and points to future studies on direct detection and collider tests.

Abstract

The scalar dark matter candidate in a prototypical theory space little Higgs model is investigated. We review all details of the model pertinent to dark matter. We perform a thermal relic density calculation including couplings to the gauge and Higgs sectors of the model. We find two regions of parameter space that give acceptable dark matter abundances. The first region has a dark matter candidate with a mass of order 100 GeV, the second region has a heavy candidate with a mass greater than about 500 GeV$. The dark matter candidate in either region is an admixture of an SU(2) triplet and an SU(2) singlet, thereby constituting a WIMP (weakly interacting massive particle).

Figures (2)

• Figure 1: Relic Density Contours for LH Models. The preferred relic density regions are displayed for $\tan \beta=0.4$. The green region illustrates a preferred value of $0.094 \leq \Omega_{dm} h^2 \leq 0.129$ and the red regions are regions where dark matter is over-produced, $\Omega_{dm} h^2 \geq 0.129$.
• Figure 2: Relic Density Contours for LH Models. This Figure is the same as Figure \ref{['fig:lhdmplot1']} but magnified to show the finer detail in the low mass region. The left plot also focuses in on the region with large $\cos^2 \vartheta_{\eta \phi}$.