Theoretical uncertainties on QCD computations and the divergence of the perturbative expansion

TL;DR

This paper investigates the divergence in QCD perturbative expansions, identifying key sources like renormalons and instantons, and models the resulting theoretical uncertainties for Higgs and top production cross sections at the LHC.

Contribution

It provides a detailed analysis of divergence sources in QCD perturbation theory and introduces a new model for estimating uncertainties from missing higher orders.

Findings

Renormalons, instantons, and the Landau pole are dominant divergence sources at different orders.

The model offers a systematic way to estimate theoretical uncertainties in Higgs and top production.

Comparison shows the model aligns well with existing uncertainty estimates.

Abstract

We analyze the divergent behaviour of the perturbative expansion in QCD, focusing on some well-known sources of divergence such as renormalons, instantons and the Landau pole divergence. We determine at which perturbative order each of these sources of divergence becomes dominant. In particular, we consider the cross section of Higgs and top production in gluon fusion at the LHC and we construct a model for the theoretical uncertainty on the missing higher orders in the perturbative expansion. We compare our model with some other existing models for theoretical uncertainty.