New developments in the 1/N expansion and non-perturbative Higgs physics

We show in this paper that the 1/N expansion is a reliable tool to calculat e the properties of a heavy Higgs boson. The 1/N expansion sums up all orde rs in perturbation theory, and therefore avoids the renormalization scheme dependence of the conventional perturbative approach, It is explained how e ffects due to the Landau pole of the Higgs sector are isolated and subtract ed, and how to perform actual calculations, by computing the Higgs line sha pe for the processes f (f) over bar --> H --> ZZ, f'(f) over bar' at next-t o-leading order in the 1/N expansion. The results are compared to the pertu rbative results to show the agreement between the perturbative and the non- perturbative approach for Higgs masses up to 1 TeV. We conclude that the th eoretical predictions for resonant production of a heavy Higgs boson at the LHC are well under control, (C) 1999 Elsevier Science B.V. All rights rese rved.