Single-spin asymmetries and soft-gluon poles

Abstract

Mechanism for the single transverse spin asymmeties in the pion production, p^\uparrow + p'\to \pi(\ell_T) + X, and the \Lambda hyperon polarization, p + p' \to \Lambda^\uparrow (\ell_T)+ X, is investigated in the framework of QCD factorization theorem. We identify all the soft-gluon pole contributions coming from the twist-3 distribution and/or fragmentation functions and show that they give rise to large asymmetries at large x_F.

Comments: Talk presented at the conference DIS2001 held at Bologna, Italy from April 27 to May 1, 2001. 4 pages with 2 figures in Latex