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.

Mixed axion-wino dark matter

“…The thermal production rates for SUSY KSVZ (which are proportional to T R ) are found in Covi et al [85], Brandenburg and Steffen [86], Strumia [87], Graf and Steffen [88] while thermal production rates for SUSY DFSZ (which are mostly independent of T R ) are obtained from Chun [89], Bae et al [90,91]. In Chun [89], Bae et al [90,91], explicit estimation is conducted for thermal axino density in SUSY DFSZ model.…”

“…In Chun [89], Bae et al [90,91], explicit estimation is conducted for thermal axino density in SUSY DFSZ model. For thermal saxion and axion production, it is reasonable to expect annihilation/production rates which are similar to axinos, so we adopt an approximate thermal production rates for saxion and axion in SUSY DFSZ model as in Bae et al [55], We include production of particles via both decays and inverse decays [55]: the latter effects are important in SUSY DFSZ where saxions and axinos are maximally produced at T ∼ m(particle) which leads to a freeze-in effect [44] which manifests itself essentially as delayed saxion/axino decays.…”

Colder freeze-in axinos decaying into photons

“…This is a well-known solution to μ-term generation by the Kim-Nilles mechanism [11]. From this interaction, freeze-in production of axinos occurs dominantly when the cosmic temperature (T) is of order of the mass of the other SUSY particle involved in the process [21][22][23]. The contributions from dimension-five anomaly operators (e.g., axino-gluino-gluon) are suppressed [22].…”

Axino dark matter in moduli-induced baryogenesis

“…As it is mentioned in refs. [34,[38][39][40], the scattering process via strong interaction is suppressed in high temperature regime. Instead, the production due to axino interaction with Higgs and Higgsino or stop and top is effective.…”

“…10 In ref. [40], the result is given for the case relativistic stop is in thermal bath and its mass is larger than µ. In such a case the yield variable is proportional to…”