  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.
