Parton Densities and Fragmentation Functions from Polarized Lambda Production in Semi-Inclusive DIS

We consider the longitudinal polarization of Lambda and Lambda-bar produced in the current fragmentation region of polarized deep inelastic scattering. We show how the various cross sections can be used to test the underlying parton dynamics, and how one can extract information about certain parton densities which are poorly known, in particular the polarized strange density sum Delta-s(x) + Delta-s-bar(x), and about fragmentation functions which are totally unknown and which are difficult to access by other means. We show also how one can obtain information concerning the intriguing question as to whether s(x) = s-bar(x) and whether Delta-s(x) = Delta-s-bar(x).