Hard exclusive production of mesons provides access to the unknown generalized parton distributions (GPDs), which give a unified description of the structure of the nucleon. Exclusive electroproduction of π+ and ρ0 mesons has been measured on an internal hydrogen gas target at HERMES by using the 27.6 GeV polarized electron or positron beam of HERA. The cross section for exclusive π+ production is presented and compared with calculations based on GPD models. For ρ0 production, the azimuthal single spin asymmetry for a transversely polarized target is sensitive to Jq, the quark total angular momentum contribution to the proton spin. Preliminary results are compared to GPD based calculations. In addition, new measurements are reported for the Spin‐Density Matrix Elements (SDMEs) for ρ0 production on an unpolarized target.

Topics
Lepton hadron interactions, Mesons, Particle beams, Particle targets, Baryons, Quantum chromodynamics, Quarks, Chemical elements, Density-matrix
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© 2006 American Institute of Physics.
2006
American Institute of Physics
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