Hunting the lightest lightest neutralinos

TL;DR

This paper explores the possibility of very light neutralino dark matter, analyzing how relaxing early universe assumptions affects their relic abundance and proposing detection strategies via direct detection and gamma-ray searches.

Contribution

It demonstrates that light neutralinos below 1 GeV can be viable dark matter candidates if early universe conditions are altered, and identifies promising detection channels.

Findings

Light neutralinos can be consistent with dark matter density under non-standard early universe conditions.

Spin-dependent detection and gamma-ray searches are promising methods for light neutralino detection.

Future linear colliders could provide crucial information on light neutralino properties.

Abstract

The lightest neutralino in the minimal supersymmetric extension of the Standard Model can be, in principle, massless. If super-light neutralinos are the dark matter, structure formation constrains their mass to be above a few keV. We show that relaxing the assumption of radiation domination and entropy conservation prior to Big Bang Nucleosynthesis, the relic abundance of very light neutralinos can be consistent with the inferred cold dark matter density. We study how we can hunt for light neutralino dark matter, with a mass at or below a GeV, focusing on both direct and indirect searches. We argue that the two most promising channels are spin-dependent direct detection and the search for monochromatic gamma rays from the prompt pair-annihilation of neutralinos into photons with GLAST. Our study indicates that the lightest lightest neutralinos can be detected as long as their mass is above a few tenth of a GeV, a mass range where a future linear collider could provide important information on the details of the particle dark matter model.