New astrophysical constraints on the mass of the superlight gravitino

Abstract

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 ( m g M Pl ) where m g and M Pl 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 ≥ m S P ≥ keV , the SN1987A observations can be used to exclude the gravitino masses in the range (10 −1.5 ≤ m g ≤ 30) eV , whereas if m S P ≤ keV , constraints of stellar energy loss can exclude the range (3 × 10 −6 ≤ m g ≤ 50) eV for the photino mass equal to 100 GeV. We also find that if m S P ≤ MeV , present understanding of big bang nucleosynthesis imply that m g ≥ eV . These are the most severe bounds to date on m g in this class of models.