Gluon-induced Higgs-strahlung at next-to-leading order QCD

TL;DR

This work computes gluon-induced contributions to Higgs-strahlung in the HHV final state (V=W/Z) at next-to-leading order in QCD, using a heavy-top, zero-bottom-mass effective theory to extract the perturbative K-factor. The LO gg-initiated amplitude arises from loop diagrams with top/bottom quarks, with Landau-Yang constraints simplifying the Z-boson couplings, and the NLO corrections are obtained by combining two-loop virtuals and real emissions via a large-mass expansion, validated by independent calculations. The resulting K-factors are around 2 for both inclusive and boosted Higgs kinematics, with residual scale uncertainties that are reduced relative to LO; the gluon-induced terms increase the total HHZZ cross section by about 4–7% depending on the collider energy. The findings support using the EFT-derived K-factor to obtain reliable NLO predictions and quantify the impact of higher-order effects on gluon-induced Higgs-strahlung, enabling improved phenomenological predictions for current and future LHC runs and inclusion in vh@nnlo.

Abstract

Gluon-induced contributions to the associated production of a Higgs and a Z-boson are calculated with NLO accuracy in QCD. They constitute a significant contribution to the cross section for this process. The perturbative correction factor (K-factor) is calculated in the limit of infinite top-quark and vanishing bottom-quark masses. The qualitative similarity of the results to the well-known ones for the gluon-fusion process $gg\to H$ allows to conclude that rescaling the LO prediction by this K-factor leads to a reliable NLO result and realistic error estimate due to missing higher-order perturbative effects. We consider the total inclusive cross section as well as a scenario with a boosted Higgs boson, where the Higgs boson's transverse momentum is restricted to values ptH>200GeV. In both cases, we find large correction factors $K\approx 2$ in most of the parameter space.

Figures (8)

• Figure 1: Representative diagrams to hadronic $\mathrm{H}$H$\mathrm{Z}$Z$$ production of Drell--Yan type up to .9 NNLO (a-f) and non-Drell--Yan-like .9 NNLO graphs with Higgs radiation off top-quark loops; both types of corrections (up to .9 NNLO) are not considered in this publication.
• Figure 2: Representative diagrams to hadronic $\mathrm{H}$H$\mathrm{Z}$Z$$ production via quark-loop-induced gluon fusion. It is understood that crossed diagrams have to be taken into account as well.
• Figure 3: Comparison of the .9 LO partonic cross section in the effective (labelled ".9 LME") and the full theory for various, partly hypothetical values of the top-quark mass. The curve for $m\mathrm{t}$t$$m_$\mathrm{t}$$=3.44$ TeV cannot be distinguished from the .9 LME result.
• Figure 4: Comparison of the .9 LO hadronic cross section in the effective and the full theory for $\sqrt{s}=8\,\mathrm{TeV}$ (dashed) and $14\,\mathrm{TeV}$ (solid).
• Figure 5: .9 N$^{}$LO hadronic cross section as obtained by using Eq. (\ref{['eq:sigmanlo']}) (upper), and .9 N$^{}$LO $K$-factor (lower) for $\sqrt{s}=8\,\mathrm{TeV}$ (dashed) and $14\,\mathrm{TeV}$ (solid).