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Measurement of deeply virtual Compton scattering off Helium-4 with CLAS at Jefferson Lab
We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off \(^4\)He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized \(^4\)He gaseous target. We detail the me...
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Published in: | arXiv.org 2021-08 |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article |
Language: | English |
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Online Access: | Get full text |
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Summary: | We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off \(^4\)He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized \(^4\)He gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling \(^4\)He nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent (\(e^4\)He$~\to~e'$$^4\(He\)'\gamma'\() beam spin asymmetries compared to those observed on the free proton, while the incoherent (\)e^4\(He\)~\to~e'\(p\)'\gamma'\(X\)'\() asymmetries exhibit a 30\)\%\( suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only \)^4\(He Compton form factor, \)\cal H_A$, leading the way toward 3D imaging of the partonic structure of nuclei. |
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ISSN: | 2331-8422 |
DOI: | 10.48550/arxiv.2102.07419 |