Leptogenesis scenarios for natural SUSY with mixed axion-higgsino dark matter

TL;DR

This paper explores leptogenesis in natural SUSY models with mixed axion-higgsino dark matter, analyzing constraints from BBN, dark matter, and dark radiation, and identifying viable parameter spaces for various leptogenesis mechanisms.

Contribution

It provides a comprehensive analysis of leptogenesis scenarios within natural SUSY models incorporating axion-higgsino dark matter, highlighting allowed parameter regions consistent with cosmological constraints.

Findings

Viable leptogenesis regions for PQ scale 10^{10}-10^{12} GeV.

Compatibility of leptogenesis with BBN, dark matter, and dark radiation constraints.

Axion masses above current ADMX search regions.

Abstract

Supersymmetric models with radiatively-driven electroweak naturalness require light higgsinos of mass ~ 100-300 GeV. Naturalness in the QCD sector is invoked via the Peccei-Quinn (PQ) axion leading to mixed axion-higgsino dark matter. The SUSY DFSZ axion model provides a solution to the SUSY mu problem and the Little Hierarchy \mu << m_{3/2} may emerge as a consequence of a mismatch between PQ and hidden sector mass scales. The traditional gravitino problem is now augmented by the axino and saxion problems, since these latter particles can also contribute to overproduction of WIMPs or dark radiation, or violation of BBN constraints. We compute regions of the T_R vs. m_{3/2} plane allowed by BBN, dark matter and dark radiation constraints for various PQ scale choices f_a. These regions are compared to the values needed for thermal leptogenesis, non-thermal leptogenesis, oscillating sneutrino leptogenesis and Affleck-Dine leptogenesis. The latter three are allowed in wide regions of parameter space for PQ scale f_a~ 10^{10}-10^{12} GeV which is also favored by naturalness: f_a~ \sqrt{\mu M_P/\lambda_\mu }\sim 10^{10}-10^{12} GeV. These f_a values correspond to axion masses somewhat above the projected ADMX search regions.