Single-spin asymmetries in the Drell-Yan process

The angular distribution of lepton pairs produced via the $q\overline{q}$ annihilation process is studied through $O\left({{\alpha }_s}^2\right)$ in perturbative QCD. Asymmetries for single-spin experiments are found to be very small in this channel. This provides an interesting new QCD test in forthcoming ${\pi }^{-}{p}^{\uparrow }$ experiments. The smallness of of the result is intimately related to the gauge structure of the theory and to the color coefficient associated with the $q\overline{q}$ subprocess.