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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.
The double-polarization observable $E$ was studied for the reaction $gamma pto pomega$ using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally-polarized frozen-spin t
The $Sigma$ beam asymmetry in $eta^{prime}$ photoproduction off the proton was measured at the GrAAL polarised photon beam with incoming photon energies of 1.461 and 1.480 GeV. For both energies the asymmetry as a function of the meson production ang
The beam-helicity asymmetry was measured, for the first time, in photoproduction of $pi^{0}eta$ pairs on carbon, aluminum, and lead, with the A2 experimental setup at MAMI. The results are compared to an earlier measurement on a free proton and to th
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
We report measurements of the photon beam asymmetry $Sigma$ for the reactions $vec{gamma}pto ppi^0$ and $vec{gamma}pto peta $ from the GlueX experiment using a 9 GeV linearly-polarized, tagged photon beam incident on a liquid hydrogen target in Jeffe