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Title: First Exclusive Measurement of Deeply Virtual Compton Scattering off He 4 : Toward the 3D Tomography of Nuclei

Here, 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 used the 6 GeV electron beam from the CEBAF accelerator at Jefferson Lab incident on a pressurized $^4$He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron was 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 was used to detect the recoiling $^4$He nuclei. We measured beam-spin asymmetries larger than those observed on the free proton in the same kinematic domain. From these, we were able to extract, in a model-independent way, the real and imaginary parts of the only $^4$He Compton form factor, $$\cal H_A$$. This first measurement of coherent deeply virtual Compton scattering on the $^4$He nucleus, with a fully exclusive final state via nuclear recoil tagging, leads the way toward 3D imaging of the partonic structure of nuclei.
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Publication Date:
Report Number(s):
JLAB-PHY-17-2543; DOE/OR/23177-4215; arXiv:1707.03361
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
AC02-06CH11357; AC05-06OR23177; SC0016583
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 119; Journal Issue: 20; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); George Washington Univ., Washington, DC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
CLAS Collaboration
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Compton scattering
OSTI Identifier:
1409646
Alternate Identifier(s):
OSTI ID: 1408936; OSTI ID: 1439894