Observation of Narrow $N^+(1685)$ and $N^0(1685)$ Resonances in $\gamma N \to \eta \pi N$ Reactions

Abstract

Observation of a narrow structure at $W\sim 1.68$ GeV in the excitation functions of some photon- and pion-induced reactions may signal a new narrow isospin-1/2 $N(1685)$ resonance. New data on the $\gamma N \to \pi \eta N$ reactions from GRAAL seems to reveal the signals of both $N^+(1685)$ and $N^0(1685)$ resonances.