PUB - Publikationen an der Universität Bielefeld

The main subject of this thesis is the exclusive [rho]0 production in polarized lepton-nucleon scattering, [my] + [Ny] -> [my]' + [Ny]' + [rho]0 , ([rho]0 -> [pi]+[pi]-). Cross section spin-asymmetries for this process are reported. These asymmetries have been determined for the first time by the Spin Muon Collaboration experiment (SMC) at CERN at low Q² in the photo-production limit and at large Q² in the kinematical range of 0.01 < Q² < 60 GeV² and 140 < W² < 310 GeV² (W = 15 GeV). In this kinematical region, the unpolarized cross section for exclusive [rho]0 production rises slowly with W, which is in general interpreted in terms of Pomeron exchange. This study, therefore, can bring for the first time direct information on the spin dependence in diffraction. About 115,000 [rho]0's have been selected from the full SMC data set. Within the statistical precision no significant asymmetries have been observed at low Q². This thesis also presents the complete and final results on the spin dependent structure functions for the proton and the deuteron from SMC in the kinematical range of 0.008 < x < 0.7 and 0.2 < Q² < 80 GeV². The QCD analysis of these data is described. The SMC results are compared to the theoretical predictions, which are the Bjorken and the Ellis-Jaffe sum rules. This comparison required a QCD evolution procedure of the data. The SMC results confirm the Bjorken sum rule, while they show that the Ellis-Jaffe sum rule is violated for both proton and deuteron, confirming the EMC findings that quarks carry only a small fraction of the nucleon's spin. The SMC experiment used longitudinally polarized high energy muon scattering from longitudinally polarized proton and deuteron targets, in order to measure the muon-proton and muon-deuteron inclusive and exclusive cross section spin-asymmetries.