Polarized Lambdas in the Current Fragmentation Region
  Data on the nucleon spin structure suggests that the $u$ (and $d$) quark distributions in the $\Lambda$ hyperon may be polarized. If this correlation carries over into fragmentation, then the study of polarized $\Lambda$'s in the current fragmentation region of deep inelastic lepton scattering will be a sensitive probe of nucleon spin structure. $\Lambda$ production by polarized electrons from unpolarized targets can search for this correlation. If it is signficant, $\Lambda$ 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 $\Lambda$, summarize electroproduction of polarized $\Lambda$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. 
R.L. Jaffe