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تسجيل مستخدم جديدFirst measurement of the helicity asymmetry $E$ in $eta$ photoproduction on the proton
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Results are presented for the first measurement of the double-polarization helicity asymmetry E for the $eta$ photoproduction reaction $gamma p rightarrow eta p$. 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 Julich 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.
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Measurements of the linearly-polarized photon beam asymmetry $Sigma$ for photoproduction from the proton of $eta$ and $eta^prime$ mesons are reported. A linearly-polarized tagged photon beam produced by coherent bremsstrahlung was incident on a cryog
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