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

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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 = 450 GeV. 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 1.2 TeV, so that gg-fusion becomes non-perturbative. Above that threshold they start to grow again and become positive around Mₕ= 1.75 TeV. The behaviour at even larger values of Mₕ shows a positive enhancement, O(+100%) at Mₕ= 3 TeV.