Higgs-Boson Contributions to Gauge-Boson Mass Shifts in Extended Electroweak Models.

In the minimal standard model, the difference between the tree-level and one-loop-corrected predictions for the gauge-boson masses, known as the mass shifts, are of the order of 4%. The domi- nant contribution is from light-fermion loops. The Higgs-dependent terms are small, even if the Higgs boson is heavy. We have analyzed the mass shifts for models with a more compli- cated Higgs sector. We use the on-shell renormalization scheme, in which the parameters of the theory are the physical masses and couplings. We have considered the 2-doublet, n-doublet, triplet and doublet -triplet models. We have found that the Z-boson mass pre - diction has a strong dependence on the charged-Higgs mass. In the limit that the charged Higgs is much heavier than the gauge bosons, the Higgs-dependent terms become significant, and may even cancel the light-fermion terms. In the models with a Higgs triplet, there is also a strong dependence of the neutral-Higgs masses, although this contribution tends to be suppressed in realistic models. The W-boson mass shift does not have a strong Higgs dependence. If we use the Z mass as input in determining the parameters of the theory, a scenario which will become attractive as the mass of the Z is accurately measured in the next few years, we find that the W-boson mass shift exhibits the same sort of behavior, differing from the minimal model for the case of the charged Higgs being heavy. We have found that when the radiative corrections are taken into account, models with extended Higgs sectors may differ significantly from the minimal standard model in their predictions for the gauge-. boson masses. Thus, an accurate measurement of the masses will help shed light on the structure of the Higgs sector. *DOE Report IS-T-1173. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.