  We discuss the effects of so-called gluonic poles in twist-three hadronic
matrix elements, as first considered by Qiu and Sterman, in the Drell-Yan
process. These effects cannot be distinguished from those of time-reversal odd
distribution functions, although time-reversal invariance is not broken by the
presence of gluonic poles. Both gluonic poles and time-reversal odd
distribution functions can lead to the same single spin asymmetries. We
explicitly show the connection between gluonic poles and large distance gluon
fields, identify the possible single spin asymmetries in the Drell-Yan process
and discuss the role of intrinsic transverse momentum of the partons.

High Energy Physics - Phenomenology