Transversly Polarized Proton-Proton Collisions and the Collins   Fragmentation Function
  The Sivers Function is briefly reviewed and the Collins Fragmentation Function to produce a hadron from a polarized quark is defined. We estimate $\pi^{+},\pi^{-}$ +X production, where X represents particles which are not detected, via proton collisions with a polarized proton target using the Collins Fragmentation Function derived using the gluon distribution functions for polarized p-p collisions at E=$\sqrt{s}$=200 GeV. 
Leonard S. Kisslinger, Ming X. Liu and Patrick McGaughey
hep-ph