Observing the Top Energy Asymmetry at the LHC

TL;DR

This paper predicts the top-antitop energy asymmetry at the LHC with next-to-leading order QCD corrections, showing it can be enhanced with phase-space cuts and providing a basis for experimental measurement.

Contribution

It offers the first detailed NLO QCD predictions for the top energy asymmetry at 13 TeV LHC, including effects of scale uncertainties and parton-shower effects.

Findings

Energy asymmetry of about -6.5% predicted after cuts.

QCD corrections have a moderate effect on the asymmetry.

Normalized asymmetry partially cancels scale and shower uncertainties.

Abstract

The top-antitop energy asymmetry is a promising observable of the charge asymmetry in jet-associated top-quark pair production at the LHC. We present new predictions of the energy asymmetry in proton-proton collisions at 13 TeV, including QCD corrections at the next-to-leading perturbative order. The effect of QCD corrections on the observable is moderate. With suitable phase-space cuts, the asymmetry can be enhanced at the cost of reducing the cross section. For instance, for a cross section of $1\,\text{pb}$ after cuts, we predict an energy asymmetry of $-6.5^{\,+0.1}_{\,-0.2}\%$ at the next-to-leading order in QCD. We also investigate scale uncertainties and parton-shower effects, which partially cancel in the normalized asymmetry. Our results provide a sound basis for a measurement of the energy asymmetry at the LHC during run II.