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Goldstino Decoupling in Spontaneously Broken Supergravity Theories

Tony Gherghetta

hep-pharXiv:hep-ph/9607448

Abstract

If the gravitino is sufficiently light and stable it will behave as an effective massless neutrino species at the time of nucleosynthesis. Depending on the temperature at which it decouples from the thermal bath in the early universe, the gravitino mass will be bounded by the primordial 4He abundance. Assuming a conservative estimate that the number of neutrino families, Nν< 3.6, superlight gravitinos with a mass m3/2 10-6eV are ruled out. This bound is weaker than previous estimates because the Goldstino annihilation cross section was overestimated.

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