Reconciling thermal leptogenesis with the gravitino problem in SUSY models with mixed axion/axino dark matter

Understand

Successful implementation of thermal leptogenesis requires re-heat temperatures T_R\agt 2\times 10^9 GeV, in apparent conflict with SUSY models with TeV-scale gravitinos, which require much lower T_R in order to avoid Big Bang Nucleosynthesis (BBN) constraints.

• We show that mixed axion/axino dark matter can reconcile thermal leptogenesis with the gravitino problem in models with m_{\tG}\agt 30 TeV, a rather high Peccei-Quinn breaking scale and an initial mis-alignment angle \theta_i < 1.
• We calculate axion and axino dark matter production from four sources, and impose BBN constraints on long-lived gravitinos and neutralinos.
• Moreover, we discuss several SUSY models which naturally have gravitino masses of the order of tens of TeV.