Single spin asymmetries in polarized proton-proton, polarized   antiproton-proton inclusive processes
  Single spin asymmetries in polarized proton(antiproton) + proton -> pion + X have been measured to be large. They can be understood within perturbative QCD by introducing new k_perp and spin dependences in fragmentation and/or distribution functions. We discuss first how these effects in distribution functions alone can account for existing data and predict single spin asymmetries in other processes; then we see how similar effects in fragmentation functions alone can fit the existing data; finally we devise strategies to discriminate between the two contributions 
M. Anselmino (1), M. Boglione (2), F. Murgia (3) ((1) University and   INFN, Torino, Italy, (2) Vrije Universiteit, Amsterda...