Gamma Rays from Super Heavy Relic Particles in the Halo

Superheavy (SH) quasistable particles generated in the Early Universe could be responsable for Ultra High Energy Cosmic Rays (UHECR) and be a component of Cold Dark Matter (CDM) in the universe. These particles are likely to cluster in the galactic halo, so that the main part of UHECR are gamma rays produced in the decay of neutral pions. Charged pions are also produced in the same decay and result in high energy electrons. We consider here the production of gamma rays by synchrotron emission of these electrons in the galactic magnetic field. The gamma ray fluxes are above the detectability level of current and proposed experiments (e.g. EGRET, GLAST, STACEE and WHIPPLE) in the energy range $0.1-10^4$ GeV and are compatible with the existing upper limits at $10^5-10^8$ GeV. The detection of this flux of gamma rays would be of key relevance to determine the importance of SH relic particles as sources of UHECR and give a clue on the physics of the Early Universe.