Gauge invariance, gluonic poles and single spin asymmetry in Drell-Yan processes

Abstract

We explore the electromagnetic gauge invariance of the hadron tensor of the Drell-Yan process with one transversely polarized hadron. The special role is played by the contour gauge for gluon fields. The prescription for the gluonic pole in the twist 3 correlator is related to causality property and compared with the prescriptions for exclusive hard processes. As a result we get the extra contributions, which naively do not have an imaginary phase. The single spin asymmetry for the Drell-Yan process is accordingly enhanced by the factor of two.

Comments: 5 pages, 1 figure; Contributed to The 19th International Spin Physics Symposium, Sept 27 - Oct 2, 2010, Juelich, Germany