Top pair production and spin correlations near threshold

The CMS and ATLAS experiments have observed spin correlation effects and a cross section excess near threshold in top-antitop production at the LHC.  They have attempted to explain these observation by assuming that they arise from the contribution of a top-antitop bound state to  the production cross section. I will discuss the dynamics of top-antitop
production and of their spin correlations near threshold, that is dominated by non-relativistic Quantum Chromodynamics Coulombic interaction. This discussion is realtively elementary, since it is carried out in the context of non-relativistic quantum mechanics. I will  show that when all non-relativistic effects are included, the description of the phenomenon cannot simply be represented by the production of a bound state, and that, on the other hand, the dominant 
effects are calculable in perturbation theory. Finally I will assess the current status of the comparison of the  experimental measurements with the theoretical calculation.