A Polarized View of the Top Asymmetry

TL;DR

This paper proposes new measurements based on charged lepton kinematics in top quark events to investigate the origin of the top forward-backward asymmetry, aiming to identify signs of new physics at the Tevatron and LHC.

Contribution

It introduces a set of observables involving charged lepton asymmetry, top polarization, and spin correlation to distinguish between new physics models causing the asymmetry.

Findings

Charged lepton asymmetry measurements can reveal new physics.

Top polarization and spin correlation help differentiate models.

Potential to establish the asymmetry at the LHC with early data.

Abstract

Recent experimental results from the CDF collaboration which study the top forward-backward asymmetry have strengthened the case that new physics is playing a role in t-tbar production. Here we propose a set of measurements, built from the charged lepton kinematics in semileptonic and fully leptonic t-tbar events, designed to further probe the underlying causes of this asymmetry both at the Tevatron and at the LHC. Using a set of conservative reference models we find that measurements of the charged lepton asymmetry, top polarization, and t-tbar spin correlation can establish the existence of new physics and distinguish between competing models both at the Tevatron and the LHC. At the Tevatron, discrimination between models is possible at the three sigma level. At the LHC, we demonstrate that a top forward-backward asymmetry can be established at roughly three sigma in the first five inverse-femtobarns of data, and show how competing explanations can be further disentangled.