Top Quark Pair Production and Asymmetry at the Tevatron and LHC in Left-Right Models

TL;DR

This paper investigates whether left-right models can explain the top quark forward-backward asymmetry discrepancy observed at the Tevatron, analyzing effects of new gauge bosons and comparing predictions with collider and flavor constraints.

Contribution

It provides a detailed analysis of top quark asymmetries within minimal and asymmetric left-right models, considering phenomenological constraints and predicting outcomes at the LHC.

Findings

Left-right models cannot fully explain the Tevatron asymmetry discrepancy.

Predicted charge asymmetries at the LHC are very small.

Model parameters consistent with existing constraints do not account for large asymmetry deviations.

Abstract

In light of the recent measurements of the top quark forward-backward asymmetry at the Fermilab Tevatron experiment, which in some regions of the parameter space shows a discrepancy of 3$\sigma$ compared to the SM prediction, we analyze top quark pair production and asymmetry in the context of left-right models both at the Tevatron and LHC. We use the minimal manifest left-right model and an asymmetric left-right model where gauge couplings and flavor mixing in the right-handed sector are allowed to differ from those in the left-handed sector. We explore the consequences of including effects from $W_R$ and $Z_R$ gauge bosons, consistent with phenomenological constraints from meson mixing and new bounds from ATLAS and CMS, for the $t \bar{t}$ cross section, invariant mass distribution and forward-backward asymmetry at the Tevatron, and predict their values at the LHC. We show that, choosing parameter benchmarks for the model while preserving agreement with collider, electroweak precision, and flavor violation data, the generic left-right model cannot account for the large deviations of the observed asymmetry at the Tevatron and also that it predicts very small charge asymmetries at the LHC.