Single spin asymmetries in hadronic processes

Single-spin asymmetry (SSA) phenomena in hadron physics are studied. The SSAs in semi-inclusive Deep Inelastic Scattering (DIS) is understood by the final-state interactions from gluon exchange between the outgoing quark and the target spectator system. The existence of such SSAs for transversely polarized nucleon targets requires a phase difference between two amplitudes coupling the proton target with to the same final-state. The asymmetry of the angular distribution in Drell-Yan processes is investigated by the SSA of the quark spin which is induced by the initial-state interactions.