Abstract
Higgs pair production through gluon fusion is an important process at the LHC to test the dynamics underlying electroweak symmetry breaking. Higgs sectors beyond the Standard Model (SM) can substantially modify this cross section through novel couplings not present in the SM or the on-shell production of new heavy Higgs bosons that subsequently decay into Higgs pairs. CP violation in the Higgs sector is important for the explanation of the observed matter-antimatter asymmetry through electroweak baryogenesis. In this work we compute the next-to-leading order (NLO) QCD corrections in the heavy top quark limit, including the effects of CP violation in the Higgs sector. We choose the effective theory (EFT) approach, which provides a rather model-independent way to explore New Physics (NP) effects by adding dimension-6 operators, both CP-conserving and CP-violating ones, to the SM Lagrangian. Furthermore, we perform the computation within a specific UV-complete model and choose as benchmark model the general 2-Higgs-Doublet Model with CP violation, the C2HDM. Depending on the dimension-6 coefficients, the relative NLO QCD corrections are affected by several per cent through the new CP-violating operators. This is also the case for SM-like Higgs pair production in the C2HDM, while the relative QCD corrections in the production of heavier C2HDM Higgs boson pairs deviate more strongly from the SM case. The absolute cross sections both in the EFT and the C2HDM can be modified by more than an order of magnitude. In particular, in the C2HDM the resonant production of Higgs pairs can by far exceed the SM cross section.
Highlights
With the discovery of the Higgs boson [1, 2], the Standard Model (SM) is structurally complete
We investigate CP violation both in a more model-independent effective theory (EFT) approach by adding additional CP-violating dimension-6 operators [65,66] and in a specific benchmark model given by the CP-violating 2-Higgs-Doublet Model (C2HDM) [67,68,69,70,71,72,73,74,75,76]
After applying the minimisation conditions of the Higgs potential, we are left with 9 input parameters for the C2HDM, which we choose as given in Eq (3.37)
Summary
With the discovery of the Higgs boson [1, 2], the Standard Model (SM) is structurally complete. The NLO QCD corrections to double Higgs production in the singlet-extended SM have been computed in [25] and those in the 2-Higgs Doublet Model (2HDM) in [51], both in the large top mass limit. In [29] we computed the NLO QCD corrections to gluon fusion into Higgs pairs including higher dimensional operators in the large top mass limit. The NNLO QCD corrections in the heavy loop particle limit have been given in [59] for the inclusive as well as the differential cross section including the relevant dimension-6 operators. In this paper we extend the NLO QCD corrections in the heavy top quark limit to Higgs sectors including CP violation.
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