Parton densities and fragmentation functions from polarized Lambda production in semi-inclusive DIS

We consider the longitudinal polarization of Lambda and <(<Lambda>)over 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 certa in parton densities which are poorly known, in particular the polarized str ange density sum Deltas(x) + Delta(s) over bar (x), and about fragmentation functions D-q(Lambda) and DeltaD(q)(Lambda) which are totally unknown and which are difficult to access by other means. We show also how one can obta in information concerning the intriguing question as to whether s(x) = (s) over bar (x) and whether Deltas(x) = Delta(s) over bar (x). (C) 2001 Publis hed by Elsevier Science B.V.