New Narrow $N(1685)$ and $N(1726)$? Remarks on the Interpretation of the Neutron Anomaly as an Interference Phenomenon

TL;DR

This paper discusses whether narrow structures observed at 1.68 and 1.72 GeV are due to interference effects or actual resonances, suggesting the possibility of new narrow nucleon states or threshold effects.

Contribution

It critically examines interference explanations and proposes the existence of new narrow resonances or threshold phenomena as more plausible causes.

Findings

Interference phenomena may not fully explain the experimental data.

Narrow resonances $N(1685)$ and $N(1726)$ are plausible explanations.

Sub-threshold virtual production effects could contribute to observed structures.

Abstract

Different interpretations of narrow structures at $W\sim 1.68$ and $W\sim 1.72$ GeV observed in several reactions are discussed. It is questionable whether interference phenomena could explain the whole complex of experimental findings. More probable hypotheses would be the existence of one or two narrow resonances $N(1685)$ and $N(1726)$ and/or the sub-threshold virtual $K\Sigma$ and $\omega p$ production (cusps).