Unusual Z0 decays in supersymmetry with a superlight gravitino.

Abstract

Supergravity theory with a superlight gravitino (of mass∼m W 2 M P1 −1 ) leads to many interesting Z 0 decay modes which are not present in the standard model or in the usual supergravity theory. We discuss the signals associated with two such decay modes, Z 0 →Sff,Pff, where S(P) is a massless scalar (pseudoscalar) particle present in this theory, and f is a quark or a lepton. Lack of observation of this mode in the current measurements at the CERN e + e − collider LEP leads to a lower bound on the gravitino mass of 10 −14 GeV.