Cosmology of the DFSZ axino

TL;DR

This paper analyzes the cosmological effects of the supersymmetric DFSZ axion model, focusing on axino production, its impact on neutralino dark matter, and the influence of the Peccei-Quinn scale on dark matter properties.

Contribution

It provides a comprehensive analysis of thermal axino production in the DFSZ model, exploring its implications for neutralino dark matter and the effects of varying the Peccei-Quinn scale.

Findings

High axino production can lead to overabundant neutralino density.

Neutralino dark matter properties depend on the Peccei-Quinn scale and axino lifetime.

Longer axino lifetime favors lighter Higgsino-like or Bino-like LSP regions.

Abstract

We study the cosmological impact of the supersymmetric DFSZ axion model. Extending recent works, we first provide a comprehensive analysis of thermal production of the DFSZ axino considering all the possible scattering, decay and inverse decay processes depending on various mass parameters and the reheat temperature. Although it is hard for the DFSZ axino to be in thermal equilibrium, its coupling is still large enough to generate huge axino population which can turn into overabundant neutralino density. We examine the neutralino parameter space to identify the dark matter property depending on the Peccei-Quinn scale. As the Peccei-Quinn scale becomes higher resulting in longer axino lifetime, the neutralino dark matter appears in a lighter Higgsino-like LSP region or a more restricted Bino-like LSP region allowing a resonant annihilation through a CP-odd Higgs boson to meet stronger reannihilation.