Analytical $O(\alpha_s)$ corrections to the beam frame double-spin   density matrix elements of $e^+e^-\to t\bar t$
  We provide analytical results for the $O(\alpha_s)$ corrections to the double-spin density matrix elements in the reaction $e^+e^-\to t\bar t$. These concern the elements $ll$, $lt$, $ln$, $tt$, $tn$, and $nn$ of the double-spin density matrix elements where $l,t,n$ stand for longitudinal, transverse and normal orientations with respect to the beam frame spanned by the electron and the top quark momentum. 
L. Kaldam\"ae, S. Groote and J.G. K\"orner
hep-ph