Light gauginos: Masses and instabilities

Abstract

Within the framework of supergravity models without grand unified steps, we analyse in detail the consequences of the hypothesis that gauginos have no bare masses due to supergravity interactions. To this purpose we have made a one-loop calculation of wino, zino, and photino masses and a renormalization group improved two-loop calculation of the gluino masses. We find that: (i) the non-observation of charged winos is compatible either with a gravitino mass m ⪅ 300 GeV or m ⪆3 TeV ; (ii) with a top quark mark of about 40 GeV, gluino and photino have very similar masses ranging from O(1 GeV) to O(20 GeV). In most cases consistency with cosmology requires that the gauge singlet needed to break the SU(2) × U(1) symmetry, be the lightest stable supersymmetric particle, with a mass as low as 1 keV or less. In such cases photino (or gluino) lifetimes into one photon (gluon) and one light singlet fermion (zerino), are typically between 10 −3 and 1 sec. We discuss the problem of the experimental detection of gauginos, which, according to the various options, require rather different approaches.