Upper Limits on the Peccei-Quinn Scale and on the Reheating Temperature in Axino Dark Matter Scenarios

TL;DR

This paper investigates constraints on the Peccei-Quinn scale and reheating temperature in axino dark matter models with long-lived charged sleptons, considering effects on big bang nucleosynthesis and potential collider signals.

Contribution

It provides new upper bounds on f_a and T_R based on axino mass, slepton lifetime, and primordial nucleosynthesis, linking cosmological constraints with collider prospects.

Findings

Temperatures above 10^9 GeV are viable for f_a > 3x10^12 GeV with axino mass > 100 keV.

Slepton lifetime can be large enough to affect primordial nucleosynthesis through bound state formation.

New upper limits on f_a and T_R depend on quantities measurable at the LHC.

Abstract

Considering axino cold dark matter scenarios with a long-lived charged slepton, we study constraints on the Peccei-Quinn scale f_a and on the reheating temperature T_R imposed by the dark matter density and by big bang nucleosynthesis (BBN). For an axino mass compatible with large-scale structure, m_axino \gtrsim 100 keV, temperatures above 10^9 GeV become viable for f_a > 3x10^12 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 f_a and on T_R that depend on quantities which will be probed at the Large Hadron Collider.