Anomalous Drell-Yan asymmetry from hadronic or QCD vacuum effects

Abstract

The anomalously large cos(2 phi) asymmetry measured in the Drell-Yan process is discussed. Possible origins of this large deviation from the Lam-Tung relation are considered with emphasis on the comparison of two particular proposals: one that suggests it arises from a QCD vacuum effect and one that suggests it is a hadronic effect. Experimental signatures distinguishing these effects are discussed.

Comments: 8 pages, 4 eps figures; Talk presented at the International Workshop on Transverse Polarization Phenomena in Hard Processes (Transversity 2005), Villa Olmo, Como, Italy, September 7-10, 2005