Analysis of the Neutralino System in Two--Body Decays of Neutralinos

In the minimal supersymmetric standard model (MSSM), the neutralinos, the spin–1/2 Majorana superpartners of the neutral gauge and Higgs bosons, are expected to be among the light supersymmetric particles that can be produced copiously at future high–energy colliders. We analyze two–body neutralino decays into a neutralino plus a $Z$ boson or a lightest neutral Higgs boson $h$, allowing the relevant parameters to have complex phases. We show that the two–body tree–level decays of neutralinos are kinematically allowed in a large region of the MSSM parameter space and they can provide us with a powerful probe of the Majorana nature and CP properties of the neutralinos through the $Z$–boson polarization measured from $Z$–boson leptonic decays.