Constraints on Neutralino masses and mixings from Cosmology and Collider Physics

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 $\approx 45-50\text{GeV}$. 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 $e^{+}{e}^{-}\to \text{x}1\text{x}2$ 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.