Complete Electroweak Corrections to Higgs production in a Standard Model with four generations at the LHC

TL;DR

This paper calculates complete electroweak two-loop corrections to Higgs production via gluon fusion in a Standard Model extended with a fourth fermion generation, revealing significant effects on production rates depending on the Higgs mass.

Contribution

It provides the first comprehensive two-loop electroweak correction analysis for Higgs production in a four-generation Standard Model, highlighting the impact of heavy fermions on the process.

Findings

Corrections are positive and large for light Higgs bosons.

Negative corrections occur around 450 GeV Higgs mass.

Corrections become huge and negative near 1.2 TeV, indicating non-perturbative behavior.

Abstract

Complete electroweak two-loop corrections to the process $gg \to H$ are presented and discussed in a Standard Model with a fourth generation of heavy fermions. The latter is studied at the LHC to put exclusion limits on a fourth generation of heavy fermions. Therefore also a precise knowledge of the electroweak(EW) next-to-leading-order(NLO) corrections is important. The corrections due to the fourth generation are positive and large for a light Higgs boson, positive but relatively small around the $\bar{t}-t$ threshold and start to become negative for a Higgs boson mass around $M_H = 450 GeV$. Increasing further the value of the Higgs boson mass, the EW NLO effects tend to become huge and negative, ${\cal O}(-100%)$, around the heavy-fermion threshold, assumed at $1.2 TeV$, so that $gg$-fusion becomes non-perturbative. Above that threshold they start to grow again and become positive around $M_H= 1.75 TeV$. The behaviour at even larger values of $M_H$ shows a positive enhancement, ${\cal O}(+100%)$ at $M_H= 3 TeV$.