On the flat transverse momentum dependence of the single-spin asymmetry   in inclusive neutral pion production
  We discuss recent experimental results from RHIC where the flat transverse momentum dependence of a single-spin asymmetry has been found in inclusive production of neutral pions. This dependence takes place in a wide region of the transverse momenta up to $p_T=10$ GeV/c. We emphasize that similar dependence has been predicted in the nonperturbative spin filtering mechanism for the single-spin asymmetries in hadron interactions and present some implications for this mechanism from the new experimental data. 
S. M. Troshin, N. E. Tyurin
hep-ph nucl-th