Single spin asymmetries in p(up arrow)p and (p)over-bar(up arrow)p inclusive processes

We consider several single spin asymmetries in inclusive p(up-arrow)p and ( p)over-bar(up-arrow)p processes as higher twist QCD contributions, taking i nto account spin and intrinsic k(perpendicular-to) effects in the quark dis tribution functions. This approach has been previously applied to the descr iption of the single spin asymmetries observed in p(up-arrow)p --> pi X rea ctions and all its parameters fixed: we give here predictions for new proce sses, which agree with experiments for which data are available, and sugges t further possible measurements. (C) 1998 Elsevier Science B.V. All rights reserved.