SUPERLIGHT NEUTRALINO AS A DARK-MATTER PARTICLE CANDIDATE

We address the question of how light the lightest supersymmetric parti cle neutralino can be to be a reliable cold dark matter (CDM) particle candidate. To this end we perform a combined analysis of the paramete r space of the minimal supersymmetric standard model (MSSM) taking int o account cosmological and accelerator constraints including those fro m the radiative b-->s gamma decay. Appropriate grand unification (GUT) scenarios are considered. We find that the relaxation of gaugino mass unification is sufficient to obtain a phenomenologically and cosmolog ically viable solution of the MSSM with a neutralino as light as 3 GeV . We find good prospects for the direct detection of these superlight CDM neutralinos via elastic scattering off various nuclei in:the forth coming experiments with low-threshold DM detectors. In a certain sense , these experiments can probe the gaugino mass unification giving cons traints on the possible GUT scenarios within the MSSM.