Polarized Lambdas in the Current Fragmentation Region

Abstract

Data on the nucleon spin structure suggests that the $u$ (and $d$) quark distributions in the $Λ$ hyperon may be polarized. If this correlation carries over into fragmentation, then the study of polarized $Λ$'s in the current fragmentation region of deep inelastic lepton scattering will be a sensitive probe of nucleon spin structure. $Λ$ production by polarized electrons from unpolarized targets can search for this correlation. If it is signficant, $Λ$ production by unpolarized electrons from longitudinally and transversely polarized targets can probe the $u$-quark helicity and transversity distributions in the nucleon. We review what is known about quark polarization in the $Λ$, summarize electroproduction of polarized $Λ$s, and estimate the sensitivity to quark polarizations in the nucleon. We also describe polarization phenomena associated with vector meson electroproduction that can be observed in the same experimental regime.