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, mover(a, ̃) ≳ 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. © 2009 Elsevier B.V. All rights reserved.