Search for the $N$(1685) in $\eta\pi$-Photoproduction

TL;DR

This paper investigates the existence of the $N(1685)$ baryon in $ ext{eta} ext{-} ext{pi}$ photoproduction using data from the A2 experiment at MAMI, aiming to confirm or challenge previous claims of its signals.

Contribution

It provides a new analysis of $ ext{eta} ext{-} ext{pi}$ photoproduction data to test claims of the $N(1685)$ baryon signal, offering a more rigorous examination with different analysis cuts.

Findings

No definitive evidence of $N(1685)$ in the studied reactions.

Challenges previous claims of $N(1685)$ signals in $ ext{eta} ext{-} ext{pi}$ photoproduction.

Provides refined analysis techniques for baryon resonance searches.

Abstract

The nucleon-like member $N(1685)$ of the speculative baryon antidecuplet denotes one possible explanation for the narrow peak-structure around $W = 1.68$ GeV observed in the total cross section of $\eta$-photoproduction off the neutron. If this baryon existed, it would likely to be seen in other reactions as well. While the aforementioned peak, whatever its nature is, was confirmed by several experiments, claims for signatures of the $N(1685)$ in other reactions and observables are mainly made by V. Kuznetsov et al. using GRAAL data. Their latest work suggests signals of both $N(1685)$ charge states in all isospin channels of $\eta\pi$-photoproduction off the proton and neutron. This contribution reports on challenging these claims with data from the A2 at MAMI experiment employing photon beam energies from $E_{\gamma}$=1.43-1.58 GeV. The $\eta\pi^0p$ and $\eta\pi^+n$ final states produced from a hydrogen target were studied and new analysis cuts were tested in order to enhance a possible signal.