Signals of a superlight gravitino at e+e− colliders when the other superparticles are heavy

Abstract

If the gravitino G̃ is very light and all the other supersymmetric particles are above threshold, supersymmetry may still be found at colliders, by looking at processes with only gravitinos and particles in the final state. We compute here the cross section for the process e +e − → G ̃ G ̃ γ , whose final state can give rise to a distinctive photon plus missing energy signal at present and future e + e − colliders. We describe how the present LEP data can be used to establish a lower bound on the gravitino mass of order 10 −5 eV. We conclude with a critical discussion of our results, comparing them with related ones and outlining possible generalizations.