Higgs production and decay with a fourth Standard-Model-like fermion generation

TL;DR

This paper provides advanced predictions for Higgs production and decay in the presence of a fourth fermion generation, highlighting significant electroweak corrections and the transition to a non-perturbative regime at high masses.

Contribution

It offers the first detailed predictions including large electroweak corrections for Higgs processes with a fourth fermion generation, emphasizing the impact on theoretical uncertainties.

Findings

Electroweak corrections can reach -50% or more for certain decay channels.

Large Yukawa couplings induce a non-perturbative regime at 400-600 GeV masses.

Significant theoretical uncertainties are associated with these predictions.

Abstract

State-of-the-art predictions for the Higgs-boson production cross section via gluon fusion and for all relevant Higgs-boson decay channels are presented in the presence of a fourth Standard-Model-like fermion generation. The qualitative features of the most important differences to the genuine Standard Model are pointed out, and the use of the available tools for the predictions is described. For a generic mass scale of 400-600 GeV in the fourth generation explicit numerical results for the cross section and decay widths are presented, revealing extremely large electroweak radiative corrections, e.g., to the cross section and the Higgs decay into WW or ZZ pairs, where they amount to about -50% or more. This signals the onset of a non-perturbative regime due to the large Yukawa couplings in the fourth generation. An estimate of the respective large theoretical uncertainties is presented as well.