Photoproduction of eta mesons from the neutron: cross sections and double polarization observable E

Abstract

Photoproduction of $\eta$ mesons from neutrons} \abstract{Results from measurements of the photoproduction of $\eta$ mesons from quasifree protons and neutrons are summarized. The experiments were performed with the CBELSA/TAPS detector at the electron accelerator ELSA in Bonn using the $\eta \to 3{\pi }^0\to 6\gamma$ decay. A liquid deuterium target was used for the measurement of total cross sections and angular distributions. The results confirm earlier measurements from Bonn and the MAMI facility in Mainz about the existence of a narrow structure in the excitation function of $\gamma n\to n\eta$. The current angular distributions show a forward-backward asymmetry, which was previously not seen, but was predicted by model calculations including an additional narrow $P_{11}$ state. Furthermore, data obtained with a longitudinally polarized, deuterated butanol target and a circularly polarized photon beam were analyzed to determine the double polarization observable $E$. Both data sets together were also used to extract the helicity dependent cross sections ${\sigma }_{1/2}$ and ${\sigma }_{3/2}$. The narrow structure in the excitation function of $\gamma n\to n\eta$ appears associated with the helicity-1/2 component of the reaction.

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Cited by in corpus (12)

• Light Baryon Spectroscopy
• Photoproduction Reactions and Non-Strange Baryon Spectroscopy
• Eta and Etaprime Photoproduction on the Nucleon with the Isobar Model EtaMAID2018
• First measurement of the polarization observable $E$ and helicity-dependent cross sections in single ${\pi }^0$ photoproduction from quasi-free nucleons
• Photo- and electro-production of narrow exotic states: from light quarks to charm and up to bottom
• Observation of Narrow $N^{+}(1685)$ and $N^0(1685)$ Resonances in $\gamma N\to \eta \pi N$ Reactions
• Photoproduction of {\boldmath{${\pi }^0$}} Mesons off Protons and Neutrons in the Second and Third Nucleon Resonance Region
• First measurement of helicity-dependent cross sections in pi0-eta photoproduction from quasi-free nucleons
• Effects of nucleon resonances on $\eta$ photoproduction off the neutron reexamined
• Photoproduction of $\eta$ mesons off the proton for $1.2<E_{\gamma }<4.7$ GeV using CLAS at Jefferson Laboratory
• Possible ${\eta }^{\prime }d$ bound state and its $s$-channel formation in the $\gamma d\to \eta d$ reaction
• Search for the $N$(1685) in $\eta \pi$-Photoproduction