The fourth generation in supergravity

We consider model-independent constraints on the fourth-generation fermion masses and the magnitude of the D-term contribution to the scalar masses. We find that the ratio of vacuum expectation values is limited to the range 1/5< or approx.vertical strokev2/v1vertical stroke< or approx.4.5. We compute the mass spectrum in the class of models where the only source of soft supersymmetry breaking is the gaugino mass msub(1/2). The lightest charged scalar turns out to be the fourth-generation slepton, which may be light enough to be pair-produced at LEP. The present PETRA bound on new charged particles implies that msub(1/2)> or approx.150 GeV. A general feature of the four-generation models is thus a heavy spectrum of sparticles. (orig.)