Interpretations and Implications of the Top Quark Rapidity Asymmetries $A_{FB}^t$ and $A_{FB}^{\ell}$

TL;DR

This paper analyzes top quark and lepton asymmetries observed at the Tevatron and LHC, exploring their relationship through spin correlations, and discusses implications for new physics models, especially those favoring right-handed top quarks.

Contribution

It provides a detailed analysis of top quark and lepton asymmetries, their connection via spin correlations, and implications for new physics models explaining the Tevatron asymmetries.

Findings

The ratio of asymmetries offers insights into new physics models.

Model favoring right-handed top quarks aligns with Tevatron data.

Updated expectations for LHC charge asymmetry based on Tevatron data.

Abstract

Forward-backward asymmetries $A_{FB}^t$ and $A_{FB}^\ell$ are observed in the top quark $t$ rapidity distribution and in the rapidity distribution of charged leptons $\ell$ from top quark decay at the Tevatron proton-antiproton collider, and a charge asymmetry $A_C$ is seen in proton-proton collisions at the Large Hadron Collider (LHC). In this paper, we update our previous studies of the Tevatron asymmetries using the most recent data. We provide expectations for $A_C$ at the LHC based first on model independent extrapolations from the Tevatron, and second based on new physics models that can explain the Tevatron asymmetries. We examine the relationship of the two asymmetries $A_{FB}^t$ and $A_{FB}^\ell$. We show their connection through the $(V-A)$ spin correlation between the charged lepton and the top quark with different polarization states. We show that the ratio of the two asymmetries provides independent insight into new physics models that are invoked to fit the top quark asymmetry. We emphasize the value of the measurement of both asymmetries, and we conclude that a model which produces more right-handed than left-handed top quarks is favored by the present Tevatron data.