Constraints on Neutralino masses and mixings from Cosmology and Collider Physics

TL;DR

This paper derives bounds on neutralino masses and mixings using cosmological relic density constraints and collider data, and proposes methods to determine neutralino couplings at future colliders.

Contribution

It provides new mass bounds on the lightest neutralino from relic density and collider measurements, and introduces a method to determine neutralino couplings at the ILC.

Findings

Neutralino mass bounds depend on GUT assumptions.

Relic density constrains neutralino mass for relativistic and non-relativistic cases.

A method to extract neutralino couplings from collider cross sections is proposed.

Abstract

Bounds on cross section measurements of chargino pair production at LEP yield a bound on the chargino mass. If the GUT relation is assumed, the lightest neutralino must be heavier than $\approx 45 -50\GeV$. If no GUT relation is assumed, no lower bound on the neutralino mass exists. I derive mass bounds on the lightest neutralino from relic density measurements for relativistic and non-relativistic neutralinos and I derive bounds on the selectron mass from the observed limits on the cross section of the neutralino pair production process $e^+e^-\to \x{1}\x{2}$ at LEP, if the lightest neutralino is massless. I further discuss radiative neutralino production and its background at the future ILC. Finally, I present a method to determine the neutralino couplings to right and left handed selectrons and Z bosons from cross section measurements of radiative neutralino production and neutralino pair production at the ILC.