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First Exclusive Measurement of Deeply Virtual Compton Scattering off He4 : Toward the 3D Tomography of Nuclei
- Source :
- Physical Review Letters. 119
- Publication Year :
- 2017
- Publisher :
- American Physical Society (APS), 2017.
-
Abstract
- We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized $^{4}\mathrm{He}$ gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling $^{4}\mathrm{He}$ nuclei. We measure beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we are able to extract, in a model-independent way, the real and imaginary parts of the only $^{4}\mathrm{He}$ Compton form factor, ${\mathcal{H}}_{A}$. This first measurement of coherent deeply virtual Compton scattering on the $^{4}\mathrm{He}$ nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.
- Subjects :
- Physics
Particle physics
Time projection chamber
Photon
Proton
Meson
010308 nuclear & particles physics
Compton scattering
General Physics and Astronomy
Electron
HERA
01 natural sciences
7. Clean energy
Nuclear physics
Recoil
0103 physical sciences
Physics::Accelerator Physics
Nuclear Experiment
010306 general physics
Subjects
Details
- ISSN :
- 10797114 and 00319007
- Volume :
- 119
- Database :
- OpenAIRE
- Journal :
- Physical Review Letters
- Accession number :
- edsair.doi...........4e6c2c5c404d44c2a1cc5aa1b45d1dc0