The (spin) structure of the nucleon
Nationaal Instituut voor Kernfysica en Hoge-Energiefysica (NIKHEF), P.O. Box 41882, 1009 DB, Amsterdam, The Netherlands
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A selection of new data obtained by the HERMES experiment at DESY is presented, which provides new insight into the QCD structure of the nucleon. Using polarized lepton beams and polarized targets, the spin-dependent structure function g 1(x) has been determined for 1 H, 2 H and 3 He. By also observing one of the produced hadrons it has been possible to extract the polarization distribution of individual quark flavours in the nucleon as well. Further information on nucleon structure has been obtained by observing (almost) exclusive reactions, which can be interpreted in terms of the recently introduced generalized parton distributions (GPDs). As an example of such data measurements of both the beam-spin and beam-charge asymmetries resulting from deeply virtual Compton scattering (DVCS) are presented. By embedding the deep-inelastic scattering process in the nuclear environment additional information can be obtained on nucleon structure and some QCD effects. The potential of this technique is illustrated by showing new results on tagged structure functions and hadronization in nuclei.
© Società Italiana di Fisica and Springer-Verlag, 2003