Charge asymmetries of top quarks at hadron colliders revisited

TL;DR

This paper revisits Standard Model predictions for top quark charge asymmetries at hadron colliders, including electromagnetic and weak corrections, and explores how cuts on transverse momentum affect asymmetry measurements, providing updated insights for Tevatron and LHC experiments.

Contribution

It provides revised Standard Model predictions for top quark charge asymmetries, incorporating electromagnetic and weak corrections, and analyzes the effects of transverse momentum cuts on asymmetry measurements at colliders.

Findings

Electromagnetic and weak corrections shift asymmetry predictions by about 10%.

Transverse momentum cuts enhance asymmetries by 30-50%.

Predictions for LHC asymmetries highlight sensitivity to new physics.

Abstract

A sizeable difference in the differential production cross section of top- compared to antitop-quark production, denoted charge asymmetry, has been observed at the Tevatron. The experimental results seem to exceed the theory predictions based on the Standard Model by a significant amount and have triggered a large number of suggestions for "new physics". In the present paper the Standard Model predictions for Tevatron and LHC experiments are revisited. This includes a reanalysis of electromagnetic as well as weak corrections, leading to a shift of the asymmetry by roughly a factor 1.1 when compared to the results of the first papers on this subject. The impact of cuts on the transverse momentum of the top-antitop system is studied. Restricting the ttbar system to a transverse momentum less than 20 GeV leads to an enhancement of the asymmetries by factors between 1.3 and 1.5, indicating the importance of an improved understanding of the $t\bar t$-momentum distribution. Predictions for similar measurements at the LHC are presented, demonstrating the sensitivity of the large rapidity region both to the Standard Model contribution and effects from "new physics".