Proton-$\eta^\prime$ interactions at threshold

TL;DR

This paper analyzes proton-$$ interactions near threshold using recent photoproduction data, determining scattering parameters and exploring the potential existence of a narrow resonance.

Contribution

It provides new measurements of the $ p$ scattering length and phase, and investigates the possible resonance with updated partial wave analysis.

Findings

Scattering length $|a_{ p}|= (0.403\u00b1 0.015\u00b1 0.060)$ fm

Phase $\u00a7=(87\u00b0 2b0)$

Indication of a possible narrow proton-$$ resonance

Abstract

Recent data on photoproduction of $\eta'$ mesons off protons have been included in the data base for the Bonn-Gatchina partial wave analysis. The real and imaginary parts of the $S$-wave $\eta^\prime p\to \eta^\prime p$ scattering amplitude in the threshold region were fit to yield the $\eta^\prime p$ scattering length and the interaction range. This new analysis found $|a_{\eta^\prime p}|= (0.403\pm 0.015\pm 0.060)$ fm and a phase $\phi=(87\pm2)^\circ$, while the range parameter is not well-constrained. The striking behavior of the GRAAL data on the beam asymmetry in the threshold region suggests that a narrow proton-$\eta'$ resonance might exist. However, the scattering length was found to be relatively insensitive to the possible existence of this narrow resonance.