NNLO predictions for Z-boson pair production at the LHC

G Heinrich,S Jahn,M Kerner,J Pires,S P Jones

doi:10.1007/jhep03(2018)142

G Heinrich, S Jahn + Show 3 more

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https://doi.org/10.1007/jhep03(2018)142

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Abstract

We present a calculation of the NNLO QCD corrections to Z-boson pair production at hadron colliders, based on the N-jettiness method for the real radiation parts. We discuss the size and shape of the perturbative corrections along with their associated scale uncertainties and compare our results to recent LHC data at sqrt{s}=13 TeV.

Highlights

NNLO contributions 0 → qZZggq 0 → qZZQQq 0 → qZZgq 0 → ggZZ 0 → qqZZ perturbative order tree-level tree-level one-loop one-loop two-loop calculation of the NNLO corrections to on-shell Z-boson pairs using a different method, based on N -jettiness subtraction [44, 45]
Virtual and real corrections come from phase space integrals of different multiplicity; a framework to combine them must be such that the divergent regions in the real-radiation contribution can be extracted and cancelled with the singularities of the virtual matrix elements
We have obtained the σNNLO(T0 > T0cut) contribution of the ZZ NNLO cross section using the tree level matrix elements from VBFNLO [65, 66] for the double-real emission phase space integral cross-checked with MadGraph5 [67], while the one-loop amplitudes for the real-virtual phase space were generated with GoSam [68, 69] and cross-checked with OpenLoops [70]

Summary

Details of the calculation

The NNLO computation requires the evaluation of the tree-level scattering amplitudes with two additional partons (double-real (RR) contribution), of the one-loop amplitudes with one additional parton (real-virtual (RV) contribution) and the two-loop corrections to the Born process (double-virtual (VV) contribution). For this reason values of T0 close to zero indicate a final state containing the ZZ pair and only IR (soft and collinear) emissions In this way the N -jettiness variable can be used as a slicing parameter in any real-radiation phase space integral to separate infrared singular regions from hard and resolved configurations. We have obtained the σNNLO(T0 > T0cut) contribution of the ZZ NNLO cross section using the tree level matrix elements from VBFNLO [65, 66] for the double-real emission phase space integral cross-checked with MadGraph5 [67], while the one-loop amplitudes for the real-virtual phase space were generated with GoSam [68, 69] and cross-checked with OpenLoops [70]. We include the loop induced one-loop squared corrections in the gg → ZZ channel, which are formally of NNLO accuracy, keeping full dependence on the top quark mass and on the Higgs mediated contributions using GoSam

Discussion of the IR subtraction procedure

Findings

Results

Conclusions