EFFECTS OF DILEPTON GAUGE BOSONS ON THE ELECTROWEAK PARAMETERS S, T AND U

We examine the contributions of dilepton gauge bosons which appear in a class of unified models to the oblique electroweak correction parameters S, T, and U. Dileptons give a negative (positive) contribution to S when singly-charged dileptons are heavier (lighter) than doubly-charged ones, while their contribution to Tis always positive semidefinite. If dileptons are the only constituents of the new physics beyond the ''reference'' Standard Model with top quark mass m(t) = 150 GeV and Higgs boson mass m(H) = 1 TeV, the recent constraints on S and T give the upper bound 590 GeV (540 GeV) on the singly-charged (doubly-charged) dilepton mass.