Threshold Resummation for the Top Quark Charge Asymmetry

TL;DR

This paper investigates the QCD charge asymmetry in top-antitop production at the Tevatron, demonstrating that threshold resummation at NLL enhances the understanding of higher-order corrections and confirms the robustness of the asymmetry predictions.

Contribution

The study applies rapidity-dependent anomalous dimension matrices to resummation, providing a more accurate prediction of the charge asymmetry including higher-order effects.

Findings

Resummation reproduces fixed-order asymmetry results.

Charge asymmetry increases with pair mass.

Threshold corrections enhance the asymmetric component.

Abstract

We study the QCD charge asymmetry in t\bar{t} production at the Tevatron. We investigate the role of higher orders in perturbation theory by considering the resummation of potentially large logarithmic corrections that arise near partonic threshold. This requires us to employ the rapidity-dependent anomalous dimension matrices that describe color mixing due to soft gluon emission in both quark- and gluon-initiated processes. The charge asymmetry appears directly in the resummed cross section at next-to-leading logarithm (NLL), and we find that the first-order expansion of the NLL resummed charge asymmetry reproduces the known fixed-order result for the asymmetry well. Beyond its lowest order, the asymmetric component of the cross section is enhanced by the same leading-logarithmic threshold corrections as the total cross section. As a result, the charge asymmetry is robust with respect to the higher-order perturbative corrections generated by threshold resummation. We observe that the asymmetry increases with pair mass and with scattering angle.