New astrophysical constraints on the mass of the superlight gravitino

In some supergravity models, the superlight gravitino is accompanied by a light weakly coupled scalar (S) and pseudoscalar particle (P). The couplings of these particles to matter (e.g. electrons and photons) is inversely proportional to the product (mg̃Mp1) where mg̃ and Mp1 are respectively the gravitino mass and the Planck mass. As a result, their emission from supernovae and stars via the reaction γ + e- → S/P + e- for certain ranges of the gravitino mass can become the dominant energy loss mechanism in contradiction with observations thereby ruling out those mass values for the gravitino. For 10 MeV ≥ mS/P ≥ keV, the SN1987A observations can be used to exclude the gravitino masses in the range (10-1.5 ≤ mg̃ ≤ 30) eV, whereas if mS/P ≤ keV, constraints of stellar energy loss can exclude the range (3 x 10-6 ≤ mg̃ ≤ 50) eV for the photino mass equal to 100 GeV. We also find that if mS/P ≤ MeV, present understanding of big bang nucleosynthesis imply that mg̃ ≥ eV. These are the most severe bounds to date on mg̃ in this class of models. © 1997 Published by Elsevier Science B.V.