Probing the Colour Structure of the Top Quark Forward-Backward Asymmetry

TL;DR

This paper investigates how QCD coherence effects can distinguish the colour structure of new physics models responsible for the top quark forward-backward asymmetry, using theoretical and simulation methods.

Contribution

It demonstrates that the dependence of the asymmetry on the pair's transverse momentum can reveal the colour structure of new physics contributions.

Findings

s-channel octet structure is favored by the data

QCD coherence effects help identify the colour nature of new physics

Different models predict distinct transverse momentum dependencies

Abstract

We point out that QCD coherence effects can help to identify the colour structure of possible new physics contributions to the anomalously large forward-backward asymmetry in top quark pair production. New physics models that yield the same inclusive asymmetry make different predictions for its dependence on the transverse momentum of the pair, if they have different colour structures. From both a fixed-order effective field theory approach and Monte Carlo studies of specific models, we find that an s-channel octet structure is preferred.