$\eta^{\prime}$ Production in Proton-Proton Collisions near Threshold
  Within the one-pion exchange model we calculate the near-threshold ${\eta}^{\prime}$ production from $pp$ collisions including the final state interaction between the protons. Since the description of the data is quite well we conclude that $\eta, \rho$ or $ \omega$ exchange currents either play no role or cancel each other to a large extent in this reaction. 
A. Sibirtsev and W. Cassing (Giessen Uni.)