Cosmology of the DFSZ axino

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.