Combination of aN$^3$LO PDFs and implications for Higgs production cross-sections at the LHC

TL;DR

This paper combines two approximate N$^3$LO PDF sets to improve Higgs production cross-section predictions at the LHC, revealing significant corrections and providing publicly available combined PDFs for enhanced phenomenological accuracy.

Contribution

It introduces a method to combine existing approximate N$^3$LO PDFs and demonstrates their impact on Higgs cross-section predictions at the LHC.

Findings

Significant corrections in Higgs production cross-sections when using combined N$^3$LO PDFs.

Combined PDFs often lead to larger effects than the differences between individual sets.

Public availability of combined N$^3$LO PDFs for LHC analyses.

Abstract

We discuss how the two existing approximate N$^3$LO (aN$^3$LO) sets of parton distributions (PDFs) from the MSHT20 and NNPDF4.0 series can be combined for LHC phenomenology, both in the pure QCD case and for the QCD$\otimes$QED sets that include the photon PDF. Using the resulting combinations, we present predictions for the total inclusive cross-section for Higgs production in gluon fusion, vector boson fusion, and associated production at the LHC Run-3. For the gluon fusion and vector boson fusion channels, the corrections that arise when using correctly matched aN$^3$LO PDFs with N$^3$LO cross section calculations, compared to using NNLO PDFs, are significant, in many cases larger than the PDF uncertainty, and generally larger than the differences between the two aN$^3$LO PDF sets entering the combination. The combined aN$^3$LO PDF sets, MSHT20xNNPDF40_an3lo and MSHT20xNNPDF40_an3lo_qed, are made publicly available in the LHAPDF format and can be readily used for LHC phenomenology.