  We study the single transverse-spin asymmetry for the inclusive direct-photon
and single-jet productions in the proton-proton collision based on the twist-3
mechanism in the collinear factorization. Taking into account all the effects
from the twist-3 quark-gluon correlation functions inside a transversely
polarized proton, we present a prediction for the asymmetries at the typical
RHIC kinematics. In both processes we find sizable asymmetries in the forward
region of the polarized proton while they are almost zero in the backward
region. This implies that if one finds a nonzero asymmetries in the backward
region in these processes, it should be ascribed wholely to the three-gluon
correlations. We also find the soft-gluon pole contribution is dominant and the
soft-fermion pole contribution is negligible in the whole Feynman-x region for
these asymmetries.
