Natural gravitino dark matter in SO(10) gauge mediated supersymmetry breaking

It is shown that gravitinos with mass m3/2∼0.1-1MeV may provide suitable cold dark matter candidates in scenarios of gauge mediated supersymmetry breaking (GMSB) under SO(10) grand unification coupled to supergravity, which accommodate a messenger sector of mass scale MX∼106GeV. This is due to the combined effects of renormalizable loop-suppressed operators and generic non-renormalizable ones governing the dilution of a pre-existing equilibrium gravitino abundance via messenger decay. The above range of gravitino and messenger masses can be accommodated in indirect GMSB scenarios. The gravitino abundance does not depend on the post-inflationary reheat temperature and it is shown that leptogenesis can generate successfully the baryon asymmetry.