Evidence for a narrow structure at W~1.68 GeV in eta photoproduction on the neutron

TL;DR

This paper reports the observation of a narrow structure at approximately 1.68 GeV in eta photoproduction on the neutron, suggesting a possible new baryon state not seen in proton data.

Contribution

It provides new experimental evidence for a narrow baryon resonance at 1.68 GeV in eta photoproduction on the neutron.

Findings

A bump-like structure at W~1.68 GeV in neutron data

No corresponding structure observed in proton data

Indicates potential existence of a narrow baryon resonance

Abstract

New results on quasi-free $\eta$ photoproduction on the neutron and proton bound in a deuteron target are presented. The $\gamma n \to \eta n$ quasi-free cross section reveals a bump-like structure which is not seen in the cross section on the proton. This structure may signal the existence of a relatively narrow ($M\sim 1.68$ GeV, $\Gamma \leq 30$ MeV) baryon state.