Pairwise final state interactions in the p d --> p d eta reaction near threshold

TL;DR

This paper revisits a model of the p d --> p d eta reaction near threshold, focusing on final state interactions, and highlights limitations of conventional FSI factors and the importance of Coulomb effects.

Contribution

It introduces a pairwise interaction approximation for the three-body final state and analyzes its implications for eta-deuteron scattering and Coulomb effects.

Findings

Limitations of conventional FSI factors in eta-deuteron scattering analysis.

Significant role of p-d final state interaction and Coulomb repulsion near threshold.

Exclusion of very large eta-nucleon scattering lengths based on model comparison.

Abstract

A model for the p d --> p d eta reaction published earlier, including the final state interaction (FSI) of all particles, is revisited to investigate the low energy data on this reaction. The three body problem of p-d-eta scattering in the final state is approximated in terms of pairwise interactions between the three particles in the final state. Apart from a comparison with some preliminary data, two new findings relevant to the near threshold data analysis are reported. The first one points toward the limitations of an FSI factor used conventionally to extract the eta-deuteron scattering length and infer subsequently on the existence of eta-mesic states. The second result emphasizes the role of the $p-d$ FSI and the strong Coulomb repulsion near threshold. Finally, a comparison of the above model calculation with low energy data, excludes very large eta-nucleon scattering lengths.