We discuss polarized parton distributions and their effects on spin asymmetries at RHIC. In particular, transversity distributions and transverse spin asymmetry are studied. First, we show the $Q^2$ evolution difference between a transversity distribution and a corresponding longitudinally polarized distribution. The difference could be an important test of perturbative QCD in high-energy spin physics. Then, the transverse spin asymmetry $A_{ TT}$ is calculated with possible transversity distributions. Next, we study antiquark flavor asymmetry $\Delta_{ _T} \bar u/ \Delta_{ _T} \bar d$ in the transversity distributions by using a simple model. Its effects on the transverse spin asymmetry are also discussed.
Categories: hep-ph hep-ex nucl-th