2015/07/31 by I. Senderovich, B. T. Morrison, M. Dugger +148 · 1 citation
Physics and Astronomy · #nucl-ex
paper · pdf · doi:10.1016/j.physletb.2016.01.044
arxiv created 2016/01/21 · arxiv updated 2016/01/27
Results are presented for the first measurement of the double-polarization helicity asymmetry E for the η photoproduction reaction γp → ηp. 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 Jülich model to examine the case for the existence of a narrow N^* 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. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.