How light can the lightest neutralino be?

TL;DR

This paper reviews the potential for a very light neutralino in the Minimal Supersymmetric Standard Model, highlighting how relaxing certain assumptions affects its mass bounds and discussing astrophysical and cosmological implications.

Contribution

It demonstrates that without GUT constraints, the lightest neutralino's mass is largely unconstrained by collider and precision data, expanding the parameter space for light neutralinos.

Findings

Neutralino mass bounds depend on GUT assumptions.

Without GUT relations, the neutralino can be arbitrarily light.

Astrophysical and cosmological considerations are discussed.

Abstract

In this talk we summarize previous work on mass bounds of a light neutralino in the Minimal Supersymmetric Standard Model. We show that without the GUT relation between the gaugino mass parameters M_1 and M_2, the mass of the lightest neutralino is essentially unconstrained by collider bounds and precision observables. We conclude by considering also the astrophysics and cosmology of a light neutralino.