Mixed axion/gravitino dark matter from SUSY models with heavy axinos

Understand

We examine dark matter production rates in supersymmetric axion models typified by the mass hierarchy m_gravitino << m_neutralino << m_axino.

• In such models, one expects the dark matter to be composed of an axion/gravitino admixture.
• After presenting motivation for how such a mass hierarchy might arise, we examine dark matter production in the SUSY Kim-Shifman-Vainshtein-Zakharov (KSVZ) model, the SUSY Dine-Fischler-Srednicki-Zhitnitsky (DFSZ) model and a hybrid model containing contributions from both KSVZ and DFSZ.
• Gravitinos can be produced thermally and also non-thermally from axino, saxion or neutralino decay.