Complete electroweak corrections to Higgs production in a Standard Model with four generations at the LHC

Complete electroweak two-loop corrections to the process gg→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 t¯-t threshold and start to become negative for a Higgs boson mass around MH=450GeV. Increasing further the value of the Higgs boson mass, the EW NLO effects tend to become huge and negative, O(−100%), around the heavy-fermion threshold, assumed at 1.2TeV, so that gg-fusion becomes non-perturbative. Above that threshold they start to grow again and become positive around MH=1.75TeV. The behavior at even larger values of MH shows a positive enhancement, O(+100%) at MH=3TeV.