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 the 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.