Soft-Gluon-Pole Contribution in Single Transverse-Spin Asymmetries of Drell-Yan Processes

Understand

We use multi-parton states to examine the leading order collinear factorization of single transverse-spin asymmetries in Drell-Yan processes.

• Twist-3 operators are involved in the factorization.
• We find that the so-called soft-gluon-pole contribution in the factorization must exist in order to make the factorization correct.
• This contribution comes from the corresponding cross-section at one-loop, while the hard-pole contribution in the factorization comes from the cross-section at tree-level.