A template method to measure the $t \bar t$ polarisation

TL;DR

This paper introduces a template method for measuring the polarization states of top-antitop quark pairs in hadron collisions, enabling detailed analysis of their spin configurations and correlations.

Contribution

The paper presents a novel template fitting technique to independently measure all polarization fractions and spin correlations of top-antitop pairs, which were previously unmeasured.

Findings

Allows extraction of individual polarization fractions

Provides measurements of net polarization and spin correlation

Applicable to arbitrary axes

Abstract

We develop a template method for the measurement of the polarisation of $t \bar t$ pairs produced in hadron collisions. The method would allow to extract the individual fractions of $t_L \bar t_L$, $t_R \bar t_R$, $t_L \bar t_R$ and $t_R \bar t_L$ pairs with a fit to data, where $L,R$ refer to the polarisation along any axis. These polarisation fractions have not been independently measured at present. Secondarily, the method also provides the net polarisation of $t$ and $\bar t$, as well as their spin correlation for arbitrary axes.