Dark Matter Gravitinos and Baryons via Q-ball decay in the Gauge-Mediated MSSM

TL;DR

This paper explores how late decay of Q-balls in the gauge-mediated MSSM can produce non-thermal NLSPs that decay into gravitino dark matter, aligning with nucleosynthesis constraints and explaining dark matter abundance.

Contribution

It provides a detailed analysis of Q-ball formation and decay in the MSSM, linking flat-direction dynamics to gravitino dark matter production without violating cosmological constraints.

Findings

Q-ball decay can produce sufficient NLSPs for dark matter

The gravitino mass range is consistent with gauge-mediated SUSY breaking

NLSPs from Q-ball decay become homogeneous and non-relativistic before annihilation

Abstract

We show that late Q-ball decay in the MSSM with gauge-mediated SUSY breaking can provide a natural source of non-thermal NLSPs which subsequently decay to gravitino dark matter without violating nucleosynthesis constraints. To show this, we perform a global analysis of Q-ball formation and decay in Affleck-Dine baryogenesis for a d = 6 (u^{c}d^{c}d^{c})^2 flat direction of the gauge-mediated MSSM. A general phenomenological potential for the flat-direction is studied and the Q-ball decay properties are obtained as a function of its parameters. The corresponding gravitino mass necessary to account for dark matter is then determined for the case of stau NLSPs. The decay temperature depends on the charge of the Q-balls, which is determined by the fragmentation of the AD condensate. Different fragmentation scenarios are considered, and the final non-thermal NLSP density from Q-ball decay and NLSP annihilation is determined. Particular care is taken to establish that NLSPs from Q-ball decay become homogeneous and non-relativistic prior to annihilation. The gravitino mass necessary for dark matter is naturally consistent with the theoretical gravitino mass in the gauge-mediation model.