Threshold Top-Quark Pair-Production: Cross Sections and Key Uncertainties

TL;DR

This paper analyzes theoretical uncertainties in top-quark pair-production near threshold at the LHC, comparing non-relativistic QCD predictions with fixed-order QCD, and discusses implications for experimental analyses.

Contribution

It provides a detailed assessment of uncertainties in top-quark pair-production predictions using non-relativistic QCD near threshold, including various parameter variations.

Findings

Predicted top-quark pair invariant-mass distribution integral: 11.67 pb with ±1.45 pb uncertainty.

Excess over fixed-order prediction: 4.15 pb with similar uncertainties.

Uncertainty sources include top-quark parameters, QCD scales, PDFs, and Green's functions.

Abstract

We study theoretical uncertainties in predicting top-quark pair-production near threshold at the LHC using the non-relativistic QCD framework. We include variations in the top-quark mass and width, the strong coupling $\alpha_s$, renormalization and factorization scales, and parton distribution functions, as well as uncertainties from the color-singlet and octet Green's functions that describe quasi-bound toponium formation. These uncertainties are compared with those from standard fixed-order QCD predictions, and implications for ATLAS and CMS analyses are discussed. For the LHC at 13 TeV center-of-mass energy, the integral of the top-quark pair invariant-mass distribution from 340 to 350 GeV is 11.67 pb with ${}^{+1.43}_{-1.47}$ pb uncertainty. The corresponding excess after subtracting the POWHEG-BOX result is 4.15 pb with the same uncertainties.