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 ≲ |ν2/ν 1| ≲ 4.5. We compute the mass spectrum in the class of models where the only source of soft supersymmetry breaking is the gaugino mass m 1 2. The lightest charged scalar turns out to be the fourth-generation slepton, which may be ligth enough to be pair-produced at LEP. The present PETRA bound on new charged particles implies that m 1 2 ≳ 150 GeV. A general feature of the four-generation models is thus a heavy spectrum of sparticles. © 1985.