Single transverse-spin asymmetries in Drell–Yan processes

The asymmetry in the angular distribution of Drell–Yan dilepton pairs produced in collisions where just one nucleon is transversely polarised has been examined in the literature with a variety of results, mainly differing by factors of two. We re-evaluate the asymmetry via twist-3 contributions in collinear factorisation. In order to allow complete and in-depth comparison with existing calculations, we supply all calculational details.