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

We show in this paper that the 1/N expansion is a reliable tool to calculate the properties of a heavy Higgs boson. The 1/N expansion sums up all orders in perturbation theory, and therefore avoids the renormalization scheme dependence of the conventional perturbative approach. It is explained how effects due to the Landau pole of the Higgs sector are isolated and subtracted, and how to perform actual calculations, by computing the Higgs line shape for the processes ff → H → ZZ, f′ f′ at next-to-leading order in the 1/N expansion. The results are compared to the perturbative results to show the agreement between the perturbative and the non-perturbative approach for Higgs masses up to 1 TeV. We conclude that the theoretical predictions for resonant production of a heavy Higgs boson at the LHC are well under control.