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Exclusive Reactions at Hermes or The Spin Budget of the Proton
Wolf-Dieter Nowak (DESY)
Seminar Room 3, 15:00
Initially, the HERMES experiment determined the 'flavour decomposition' of
the nucleon spin. "Polarized" Parton Distribution Functions for u,d, and s
quarks were measured in 'semi-inclusive' hadron production. More recently,
the concept of Generalized Parton Distributions opened access to the total
angular momentum of u and d quarks. Here, certain cross section asymmetries
were measured in 'exclusive' production of a real photon (Deeply Virtual
Compton Scattering) or a scalar or vector meson. Results from HERMES and
other experiments are compared and confronted to contemporary theoretical
models. The present status of the understanding of the spin budget of the
nucleon is summarized.
