Constraints on Asymmetric Dark Matter Self Annihilation Cross Sections

TL;DR

This paper explores how different early universe models affect the relic density and self-annihilation limits of asymmetric dark matter, providing new constraints on particle masses in these scenarios.

Contribution

It introduces the effects of shear-dominated and Gauss-Bonnet braneworld cosmologies on asymmetric dark matter evolution and self-annihilation constraints.

Findings

Shear-dominated universe allows higher self-annihilation cross section limits.

Gauss-Bonnet braneworld results in lower upper limits on self-annihilation cross sections.

Constraints on wino mass differ between the two cosmological models.

Abstract

We investigate the evolution of the relic density for asymmetric dark matter incorporating self annihilation processes in both the shear-dominated universe and Gauss-Bonnet braneworld. Under the same conditions where the ratio of final asymmetry to the initial asymmetry $ R \equiv \Delta_{-\infty}/\Delta_{\text{in}} $ is identical, the shear-dominated universe, due to its enhanced Hubble expansion rate, leads to an earlier freeze-out point of wash-out asymmetry process and allows a higher upper limit on the self annihilation cross section. Conversely, the Gauss-Bonnet braneworld, with a weakened Hubble expansion rate, delays the freeze-out point and permits a lower upper limit on the self annihilation cross section. We further constrain the wino mass $M_2$ for sneutrino and higgsino asymmetric dark matter in both scenarios, showing that, compared to the standard model, the lower limit of $M_2$ is smaller in the shear-dominated universe but higher in the Gauss-Bonnet braneworld.