Recent data on photoproduction of η′ 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 η′p→η′p scattering amplitude in the threshold region were fit to yield the η′p scattering length and the interaction range. This new analysis found ∣aη′p∣=(0.403±0.015±0.060) fm and a phase ϕ=(87±2)∘, 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-η′ resonance might exist. However, the scattering length was found to be relatively insensitive to the possible existence of this narrow resonance.
@article{arxiv.1803.06814,
title = {Proton-$\eta^\prime$ interactions at threshold},
author = {A. V. Anisovich and V. Burkert and M. Dugger and E. Klempt and V. A. Nikonov and B. G. Ritchie and A. V. Sarantsev and U. Thoma},
journal= {arXiv preprint arXiv:1803.06814},
year = {2018}
}