Top quark asymmetry from a non-Abelian horizontal symmetry

TL;DR

This paper explores a non-Abelian flavor gauge symmetry model to explain the large top quark forward-backward asymmetry observed at the Tevatron, analyzing its implications for collider signatures and experimental constraints.

Contribution

It introduces a non-Abelian flavor gauge symmetry framework to account for the top asymmetry and discusses its phenomenological signatures at the LHC.

Findings

Gauge boson exchange can produce large asymmetry via Rutherford scattering.

Potential LHC signatures include increased top pair production and like-sign dilepton events.

Challenges in comparing theory to experiment due to acceptance effects.

Abstract

Motivated by the persistence of a large measured top quark forward-backward asymmetry at the Tevatron, we examine a model of non-Abelian flavor gauge symmetry. The exchange of the gauge bosons in the $t$-channel can give a large asymmetry due to the forward Rutherford scattering peak. We address generic constraints on non-Abelian $t$-channel physics models including flavor diagonal resonances and potentially dangerous contributions to inclusive top pair cross sections. We caution on the general difficulty of comparing theoretical predictions for top quark signals to the existing experimental results due to potentially important acceptance effects. The first signature at the Large Hadron Collider can be a large inclusive top pair cross section, or like-sign dilepton events, although the latter signal is much smaller than in Abelian models. Deviations of the invariant mass distributions at the LHC will also be promising signatures. A more direct consistency check of the Tevatron asymmetry through the LHC asymmetry is more likely to be relevant at a later stage.