Forward-backward asymmetry of top quark in diquark models

TL;DR

This paper explores how diquark models, specifically color-triplet diquarks, can explain the large forward-backward asymmetry of top quarks observed at the Tevatron, offering a u-channel mechanism as an alternative to other models.

Contribution

It introduces diquark models as a new explanation for the top quark FBA, highlighting the u-channel process and quantifying the asymmetry achievable within these models.

Findings

Color-triplet diquarks can produce a 20% FBA.

The model is consistent with top pair production cross section constraints.

U-channel diagrams are key to the asymmetry in diquark models.

Abstract

Motivated by the recent unexpected large forward-backward asymmetry (FBA) of the top quark observed by D$\O$ and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models. Unlike other mechanisms induced by s-channel or t-channel, the top-quark pair production in the diquark models is dictated by the u-channel diagram. We find that the color-triplet diquark can generate the FBA of 20% when the constraint from the cross section of the top-quark pair production is taken into account.