  We study the single transverse-spin asymmetry for the Drell-Yan lepton pair
production based on the twist-3 mechanism in the collinear factorization. We
calculate all the hard-pole (HP) and the soft-fermion-pole (SFP) contributions
to the single-spin-dependent cross section originating from the quark-gluon
correlation functions in the transversely polarized nucleon in the leading
order with respect to the QCD coupling constant. Combined with the
soft-gluon-pole (SGP) contribution, this completes the corresponding twist-3
cross section. In the real photon limit, where all the HP contributions are
transformed into the SFP contribution, we find that the SFP partonic hard cross
section for the two independent quark-gluon correlation functions coincides in
each scattering channel, as in the case of the inclusive light-hadron
production. Our result enables one to extract the quark-gluon correlation
functions from the forthcoming experiments at several facilities such as RHIC
and J-PARC.
