Collins Effect in SIDIS and in ${\mathbf{e}}^{+}{\mathbf{e}}^{-}$ Annihilation

Abstract

We review the present understanding of the nucleon transversity distribution and Collins fragmentation function, based on Ref.\cite{Efremov:2006qm}, and discuss how Drell-Yan experiments will improve it.

Comments: Talk at Moscow ICHEP 26.7-2.8.2006 and Kyoto Symposium on Spin Physics 2-7.10.2006, 5 pages, 5 figures, AIP style files included. Some pictures chenged, one reference added, typos and some errors in formulas are corrected