Forward Tevatron Tops and Backward LHC Tops with Associates

TL;DR

This paper proposes a model involving a Z' resonance with flavor off-diagonal couplings to explain the observed top quark asymmetries at Tevatron and LHC, reconciling experimental data with theoretical predictions.

Contribution

It introduces a specific Z' model with flavor off-diagonal couplings that accounts for both forward-backward and charge asymmetries in top quark production, consistent with various experimental constraints.

Findings

The Z' model reproduces the asymmetry data.

The model is compatible with collider and atomic parity constraints.

It offers a unified explanation for Tevatron and LHC top asymmetries.

Abstract

The anomalous forward-backward asymmetry (A_FB) in t tbar production at the Tevatron is in apparent contradiction with the t tbar charge asymmetry (A_C) measurements at the LHC, which agree well with the standard model predictions. We argue that associated production of a state with [u tbar] flavor quantum numbers can lead to a sizable negative contribution to A_C. Exchange of such a resonance in the t-channel would lead to positive contributions to A_FB and A_C, as has been extensively discussed in the literature. Given the additional negative A_C contribution, both the Tevatron and LHC data can be naturally accommodated within this framework. A simple realization of this setup is the well known example of a Z' with flavor off-diagonal up-top couplings. We provide a detailed study of this model, demonstrating that it indeed reproduces the t tbar asymmetry data, and is compatible with other constraints, e.g. t+jet resonance searches, t tbar inclusive jet multiplicities, and atomic parity violation.