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

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.