Hadronic decays of cosmological gravitinos

We discuss a variety of effects due to the thermalisation and possible annihilation of relativistic protons and antiprotons from the decay of cosmological gravitinos. For a rather narrow range of gravitino mass around 250 GeV, the photons produced by inverse “Compton” scattering of nucleons off the thermal radiation are of the right energy to photodissociate helium 4, creating deuterium and helium 3. In a supersymmetric inflationary universe, this leads to a maximum reheating temperature of about 1.2 × 10 7 GeV for this particular gravitino mass.