Upper limits on the Peccei–Quinn scale and on the reheating temperature in axino dark matter scenarios

Abstract

Considering axino cold dark matter scenarios with a long-lived charged slepton, we study constraints on the Peccei–Quinn scale fa and on the reheating temperature TR imposed by the dark matter density and by big bang nucleosynthesis (BBN). For an axino mass compatible with large-scale structure, ma˜≳100 keV, temperatures above 109 GeV become viable for fa>3×1012 GeV. We calculate the slepton lifetime in hadronic axion models. With the dominant decay mode being two-loop suppressed, this lifetime can be sufficiently large to allow for primordial bound states leading to catalyzed BBN of lithium-6 and beryllium-9. This implies new upper limits on fa and on TR that depend on quantities which will be probed at the Large Hadron Collider.