Three-gluon contribution to the single spin asymmetry for light hadron production inppcollision

We study the twist-3 three-gluon contribution to the single spin asymmetry in the light-hadron production in pp collision in the framework of the collinear factorization. We derive the corresponding cross-section formula in the leading order with respect to the QCD coupling constant. We also present a numerical calculation of the Relativistic Heavy Ion collider (RHIC) energy, using a model for the three-gluon correlation functions suggested by the asymmetry observed in the D-meson production at the RHIC.