SUPERNOVA CONSTRAINTS ON A SUPERLIGHT GRAVITINO

In supergravity models with low supersymmetry-breaking scale, the grav itinos can be superlight, with mass in the 10(-6) eV to a few keV rang e. In such a case, gravitino emission provides a new cooling mechanism for protoneutron stars and therefore can provide constraints on the m ass of a superlight gravitino. This happens because the coupling to ma tter of superlight gravitinos is dominated by its Goldstino component, whose coupling to matter is inversely proportional to the scale of su persymmetry breaking and increases as the gravitino mass decreases. Pr esent observations therefore provide lower limits on the gravitino mas s. Using the recently revised Goldstino couplings, we find that the tw o dominant processes in supernova cooling are e(+)e(-) --> (G) over ti lde (G) over tilde and gamma+e(-) --> e(-) (G) over tilde (G) over til de. They lead to a lower limit on the supersymmetry-breaking scale Lam bda(S) from 160 to 500 GeV for core temperatures 30 to 60 MeV and elec tron chemical potentials 200 to 300 MeV. The corresponding lower limit s on the gravitino mass are 0.6 to 6X10(-6) eV. [S0556-2821(98)00603-1 ].