Abstract
Exclusive ω meson production is studied by the COMPASS Collaboration using the CERN 160 GeV/ c muon beam and a transversely polarised proton target. Single-spin and double-spin asymmetries are measured, some of which are sensitive to the Generalised Parton Distributions E that are related to quark orbital angular momenta. The results, which are sensitive also to the pion-pole contribution to the production mechanism, are compared to the predictions of a phenomenological model.
Highlights
Hard exclusive electro and muoproduction of mesons on nucleons has been playing an important role in studies of the hadron structure
Renewed interest arose when it was shown that it allows access to Generalised Parton Distributions (GPDs), which provide a comprehensive description of the partonic structure of the nucleon and contain a wealth of new information
Using GPDs the nucleon can be described as an extended object, which is referred to as 3-dimensional nucleon tomography, and access to quark orbital angular momentum becomes possible in principle
Summary
Hard exclusive electro and muoproduction of mesons on nucleons has been playing an important role in studies of the hadron structure. Renewed interest arose when it was shown that it allows access to Generalised Parton Distributions (GPDs), which provide a comprehensive description of the partonic structure of the nucleon and contain a wealth of new information. The chiral-even GPDs H and E are sufficient to describe exclusive vector meson production on a spin-. These GPDs are of special interest as they are related to the total angular momentum carried by partons in the nucleon [1]. The interpretation of the COMPASS results presented in this article is done in the framework of the GPD-. The model includes some estimation of the pion-pole contribution to the mechanism of exclusive ω production [2], which is sizeable at COMPASS kinematics. A full account of the content of this article is given in Ref. [4]
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