PRECISION OBSERVABLES IN SU(2)XU(1) MODELS WITH AN ADDITIONAL HIGGS TRIPLET

Electroweak precision observables are calculated at complete one-loop order in the extension of the standard model by an extra Higgs triplet , where the rho-parameter can be different from unity already at the t ree level. One additional data point is required for fixing the input parameters. In the on-shell renormalization scheme the leptonic mixing angle sin(2) theta(e) at the Z peak is chosen, together with the conv entional input alpha, M-Z, G(mu), m(t). The calculated observables dep end on the mass of the doublet Higgs boson H-0 and on the masses of th e extra non-standard Higgs bosons as free parameters. The predictions of the standard model and the triplet model coincide for all observabl es in the experimental range of the top mass. In the triplet model, al l observables which show a dependence on the doublet Higgs mass M-H0 a re consistent with a low value of M-H0. (C) 1998 Elsevier Science B.V.