Dynamical Origin of the Correlation between the Asymmetries $A_{FB}^t$ and $A_{FB}^{\ell}$

TL;DR

This paper investigates the relationship between the forward-backward asymmetries in top quark pairs and their decay leptons, exploring the role of spin correlations and new physics models to explain experimental observations.

Contribution

It provides a detailed analysis of the kinematic and dynamic origins of the asymmetry correlation, considering new physics models and emphasizing the importance of both measurements.

Findings

Models with more right-handed top quarks fit the data better.

Spin correlations explain the relationship between $A_{FB}^t$ and $A_{FB}^ ext{l}$.

New physics models like axigluons and $W'$ can account for the observed asymmetries.

Abstract

A larger than expected forward-backward asymmetry in rapidity is observed in top quark pairs produced in proton-antiproton collisions at the Tevatron. The asymmetry is seen in both the top quark distribution $A_{FB}^t$ and in the distribution of charged leptons $A_{FB}^\ell$ from top quark decay. In this paper, we study the kinematic and dynamic aspects of the tight relationship of the two observables arising from the spin correlation between the charged lepton and the top quark with different polarization states. We also consider two benchmark new physics models, an axigluon model and a flavor-changing $W^\prime$ model. These models could explain the values of both $A_{FB}^t$ and $A_{FB}^\ell$. We emphasize the value of both measurements, and we conclude that a model which produces more right-handed than left-handed top quarks is favored by the present data.