Dark radiation and dark matter in supersymmetric axion models with high reheating temperature

TL;DR

This paper investigates supersymmetric axion models with high reheating temperatures to explain observed extra radiation and cold dark matter, analyzing scenarios with gravitino or axion dark matter and their cosmological implications.

Contribution

It introduces two high-reheating-temperature scenarios within supersymmetric axion models that account for both extra radiation and cold dark matter, consistent with recent cosmological data.

Findings

Axions from saxion decays provide early extra radiation before BBN.

Late decays of axinos and gravitinos produce additional radiation compatible with observations.

Models are testable via axion searches at ADMX and supersymmetric particle detection at LHC.

Abstract

Recent studies of the cosmic microwave background, large scale structure, and big bang nucleosynthesis (BBN) show trends towards extra radiation. Within the framework of supersymmetric hadronic axion models, we explore two high-reheating-temperature scenarios that can explain consistently extra radiation and cold dark matter (CDM), with the latter residing either in gravitinos or in axions. In the gravitino CDM case, axions from decays of thermal saxions provide extra radiation already prior to BBN and decays of axinos with a cosmologically required TeV-scale mass can produce extra entropy. In the axion CDM case, cosmological constraints are respected with light eV-scale axinos and weak-scale gravitinos that decay into axions and axinos. These decays lead to late extra radiation which can coexist with the early contributions from saxion decays. Recent results of the Planck satellite probe extra radiation at late times and thereby both scenarios. Further tests are the searches for axions at ADMX and for supersymmetric particles at the LHC.