Abstract: A2 Collaboration at MAMI. Precise helicity-dependent cross sections and the double-polarization observable E were measured for $\eta$ photoproduction from quasifree protons and neutrons bound in the deuteron. The $2\gamma$ and $3\pi^0$ decay modes were used to optimize the statistical quality of the data and to estimate systematic uncertainties. The measurement used the A2 detector setup at the tagged photon beam of the electron accelerator MAMI in Mainz. A longitudinally polarized deuterated butanol target was used in combination with a circul...
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