Results are presented for the first measurement of the double-polarization helicity asymmetry E for the Î· photoproduction reaction Î³pâÎ·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 JÃ¼lichâBonn model to examine the case for the existence of a narrow Nâ 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 from that model. Further comparison with several theoretical approaches indicates these data will significantly enhance our understanding of nucleon resonances.
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|Titolo:||First measurement of the helicity asymmetry E in Î· photoproduction on the proton|
|Data di pubblicazione:||2016|
|Appare nelle tipologie:||03.1 Articolo su rivista|