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Spin transfer in deep-inelastic ⌳ electroproduction has been studied with the HERMES detector using the 27.6 GeV polarized positron beam in the DESY HERA storage ring. For an average fractional energy transfer ͗z͘ϭ0.45, the longitudinal spin transfer from the virtual photon to the ⌳ has been extracted. The spin transfer along the ⌳ momentum direction is found to be 0.11Ϯ0.17(stat)Ϯ0.03(syst); similar values are found for other possible choices for the longitudinal spin direction of the ⌳. This result is the most precise value obtained to date from deep-inelastic scattering with charged lepton beams, and is sensitive to polarized up quark fragmentation to hyperon states. The experimental result is found to be in general agreement with various models of the ⌳ spin content, and is consistent with the assumption of helicity conservation in the fragmentation process.

Single-spin asymmetries have been measured for semi-inclusive electroproduction of pi(+), pi(-), pi(0) and K+ mesons in deep-inelastic scattering off a longitudinally polarised deuterium target. The asymmetries appear in the distribution of the hadrons in the azimuthal angle phi around the virtual photon direction, relative to the lepton scattering plane. The corresponding analysing powers in the sinphi moment of the cross section are 0.012 +/- 0.002(stat.) +/- 0.002(syst.) for pi(+), 0.006 +/- 0.003(stat.) +/- 0.002(syst.) for pi(-), 0.021 +/- 0.005(stat.) +/- 0.003(syst.) for pi(0) and 0.013 +/- 0.006(stat.) +/- 0.003(syst.) for K The sin 20 moments are compatible with zero for all particles. (C) 2003 Elsevier Science B.V All rights reserved