Coherent photoproduction of eta-mesons off 3He - search for eta-mesic nuclei

Abstract

Coherent photoproduction of $\eta$-mesons off ${}^3$He, i.e. the reaction ${\gamma }^{3}He\to {\eta }^{3}He$, has been investigated in the near-threshold region. The experiment was performed at the Glasgow tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball - TAPS detector. Angular distributions and the total cross section were measured using the $\eta \to \gamma \gamma$ and $\eta \to 3{\pi }^0\to 6\gamma$ decay channels. The observed extremely sharp rise of the cross section at threshold and the behavior of the angular distributions are evidence for a strong $\eta {}^{3}He$ final state interaction, pointing to the existence of a resonant state. The search for further evidence of this state in the excitation function of ${\pi }^0$-proton back-to-back emission in the ${\gamma }^{3}He\to {\pi }^{0}pX$ reaction revealed a very complicated structure of the background and could not support previous conclusions.

accepted for publication in Phys. Lett. B

References in corpus (9)

• Upgrade of the Glasgow photon tagging spectrometer for Mainz MAMI-C
• Measurement of the dp -->3He eta reaction near threshold
• Quasi-free photoproduction of eta-mesons of the neutron
• Is there an eta-3He quasi--bound state ?
• Quasi-free photoproduction of eta-mesons off the deuteron
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• Cross Section and Tensor Analysing Power of the $\vec{d}d\to \eta \alpha$ Reaction Near Threshold
• Photoproduction of eta-mesons off nuclei for Eg < 2.2 GeV
• Precision study of the d+p->3He+eta reaction for excess energies between 20 and 60 MeV

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