Cosmological constraints on the scale of supersymmetry breaking

We consider the cosmological and astrophysical constraints on the decay of massive E8 xE8' superstring axions associated with the hidden sector. We find that decay lifetimes greater than 1 s are ruled out by limits from nucleosynthesis, by limits on the distortion of the cosmic microwave and gamma ray backgrounds and by closure arguments. We conclude that Λ>1.2x1013 GeV, where Λ is the scale of gaugino condensation in the hidden sector. This implies that the scale of supersymmetry breaking is greater than 1010 GeV. Significantly, our result agrees with the value of 5x1013 GeV for Λ obtained independently by setting supersymmetric scalar masses equal to mW. (orig.)