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This thesis is devoted to the measurement of double-spin asymmetries in the cross section of exclusive diffractive electroproduction and quasi-real photoproduction of ρand φ-mesons in the kinematic region of HERMES, characterized by < Q >= 1.8 GeV, < W 2 >= 24.5 GeV, and < x >= 0.07. Data used for this analysis were collected with the HERMES experiment in the years 1996-2000 using the longitudinally polarized lepton beam of HERA and the internal target of HERMES, filled with longitudinally polarized protons and deuterons. The purpose of this measurement was to tag the parity of the object exchanged in the tchannel of the interaction of the vector-meson state with the nucleon and thereby to test different theoretical models of vector-meson production mechanisms. The photon-absorption asymmetry in exclusive ρ-production on the deuteron target was measured to be consistent with zero, while this asymmetry on the proton target was confirmed to be slightly positive. These results are consistent with different theoretical predictions for a significant contribution of unnatural-parity object exchange (either Reggeon or di-quark object) to exclusive ρ-production. The photon-absorption asymmetries in exclusive φ-production are measured to be consistent with zero for both proton and deuteron targets. These measurements agree with the prediction of Pomeron-exchange dominance in φ-meson production. The dependence of the asymmetries on kinematic variables was investigated. At very low Q (quasi-real photoproduction regime) the double-spin asymmetries for ρand φ-mesons are measured to be consistent with zero for both proton and deuteron targets. No theoretical expectation for the value of the double-spin asymmetry at very low Q exists, up to now. Altogether, the conclusion is drawn that at the intermediate energies of the HERMES experiment ρ-meson production follows the Generalized Vector Meson Dominance scheme with subsequent scattering of the vector-meson state off the nucleon proceeding via exchange of both Reggeon(s) and Pomeron(s) in the t-channel.

Double-spin asymmetries in diffractive vector-meson production at HERMES