Longitudinal target-spin asymmetries for deeply virtual Compton scattering

Abstract

A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for $ep\to e^{\prime }{p}^{\prime }\gamma$ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in $Q^2$, $x_B$, $t$ and $\varphi$, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the $t$ dependence of these asymmetries provides insight on the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even GPDs.

7 pages, 4 figures

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• Matching Quasi Generalized Parton Distributions in the RI/MOM scheme
• Single and double spin asymmetries for deeply virtual Compton scattering measured with CLAS and a longitudinally polarized proton target
• Tomographic image of the proton
• An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab
• First Exclusive Measurement of Deeply Virtual Compton Scattering off ${}^4$He: Toward the 3D Tomography of Nuclei
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• Dense Baryonic Matter and Strangeness in Neutron Stars
• Deeply virtual Compton scattering in the tensor-pomeron approach
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• New framework for extracting GPDs from exclusive photon electroproduction