Forward-backward asymmetry in top quark-antiquark production

TL;DR

This paper measures the forward-backward asymmetry in top quark-antiquark production at the Fermilab Tevatron, finding a higher asymmetry than predicted by standard NLO QCD models, with implications for understanding top quark dynamics.

Contribution

First measurement of top quark forward-backward asymmetry in lepton+jets final state at the Tevatron, including corrected asymmetries and comparison to NLO QCD predictions.

Findings

Measured asymmetry at reconstruction level: 9.2%

Corrected asymmetry: 19.6%

Lepton-based asymmetry: 15.2%

Abstract

We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a dataset corresponding to an integrated luminosity of $5.4\,\mathrm {fb}^{-1}$, collected by the \DZ\ experiment at the Fermilab Tevatron Collider, we measure the \ttbar\ forward-backward asymmetry to be $(9.2 \pm 3.7)$% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be $(19.6 \pm 6.5)$%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be $(15.2 \pm 4.0)$%. The results are compared to predictions based on the next-to-leading-order QCD generator {\sc mc@nlo}. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.