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Title: First measurement of the helicity asymmetry E in η photoproduction on the proton

Results are presented for the first measurement of the double-polarization helicity asymmetry E for the η photoproduction reaction γ p → η p. Data were obtained using the FROzen Spin Target (FROST) with the CLAS spectrometer in Hall B at Jefferson Lab, covering a range of center-of-mass energy W from threshold to 2.15 GeV and a large range in center-of-mass polar angle. As an initial application of these data, the results have been incorporated into the J\"ulich model to examine the case for the existence of a narrow Ν* resonance between 1.66 and 1.70 GeV. The addition of these data to the world database results in marked changes in the predictions for the E observable using that model. As a result, further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2]
  1. Arizona State Univ., Tempe, AZ (United States)
  2. Arizona State Univ., Tempe, AZ (United States). et al.
Publication Date:
Report Number(s):
JLAB-PHY-15-2096; DOE/OR/23177-3461; arXiv:1507.00325
Journal ID: ISSN 0370-2693
Grant/Contract Number:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 755; Journal Issue: C; Journal ID: ISSN 0370-2693
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
eta photoproduction; polarization observable; helicity asymmetry
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1235997