Double Helicity Asymmetry and Cross Section for eta Production in   Polarized pp Collisions at PHENIX
  Measurements of double helicity asymmetries for inclusive hadron production in polarized proton-proton collisions are sensitive to spin-dependent parton distribution functions, in particular to the gluon distribution, Delta g. This study presents the double helicity asymmetry and the cross section for eta production. The cross section measurement yields valuable data for the extraction of the fragmentation functions, which are unknown at present but are a prerequisite for the extraction of the spin-dependent parton distribution functions. 
Frank Ellinghaus (for the PHENIX Collaboration)