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Published December 1, 2001 | Published
Journal Article Open

Measurement of longitudinal spin transfer to Λ hyperons in deep-inelastic lepton scattering


Spin transfer in deep-inelastic Λ 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 〈z〉=0.45, the longitudinal spin transfer from the virtual photon to the Λ has been extracted. The spin transfer along the Λ momentum direction is found to be 0.11±0.17(stat)±0.03(syst); similar values are found for other possible choices for the longitudinal spin direction of the Λ. 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 Λ spin content, and is consistent with the assumption of helicity conservation in the fragmentation process.

Additional Information

© 2001 The American Physical Society. Received 4 May 2001; published 8 November 2001. We gratefully acknowledge the DESY management for its support and the DESY staff and the staffs of the collaborating institutions. This work was supported by the FWO Flanders, Belgium; the Natural Sciences and Engineering Research Council of Canada; the INTAS, HCM, and TMR network contributions from the European Community; the German Bundesministerium für Bildung und Forschung; the Deutscher Akademischer Austauschdienst (DAAD); the Italian Istituto Nazionale di Fisica Nucleare (INFN); Monbusho, JSPS, and Toary Science Foundation of Japan; the Dutch Foundation for Fundamenteel Onderzoek der Materie (FOM); the U.K. Particle Physics and Astronomy Research Council; and the U.S. Department of Energy and National Science Foundation.

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