Longitudinal spin-transfer in Λ production at HERMES

Spin transfer in deep-inelastic A electroproduction has been studied with the HERMES detector using the 27.6-GeV polarized positron beam in the HERA storage ring. The longitudinal spin transfer D-LL' from the virtual photon to the A has been extracted as a function of z, the fraction of the virtual photon energy carried by the A. The observable D-LL' is sensitive to both helicity conservation in the fragmentation process and to hyperon spin structure. Including all data taken at HERMES during the years 1996-2000, a preliminary average value of D (LL') = 0.04 0.09 is obtained in the current fragmentation region x(F) > 0. These results are explained by a Monte Carlo simulation based on the Lund string model. The principal conclusion of these studies is that even in the forward-production region x(F) > 0, A production in medium-energy deep-inelastic scattering is complicated by the influence of the target remnant.