The role of $N^{*}(1535)$ in $\eta '$ production

TL;DR

This paper investigates the production mechanism of $ ext{η'}$ mesons near threshold, highlighting the dominance of t-channel π exchange and the significant coupling of $N^{*}(1535)$ to $ ext{η'} N$, with implications for the resonance's internal structure.

Contribution

It introduces an effective Lagrangian model emphasizing the role of $N^{*}(1535)$ in $ ext{η'}$ production and predicts the cross-section ratio between pn and pp collisions.

Findings

t-channel π exchange dominates $ ext{η'}$ production

Predicted ratio $rac{\sigma(pn o pn ext{η'})}{\sigma(pp o pp ext{η'})} ext{ is 6.5}

Strong coupling of $N^{*}(1535)$ to $ ext{η'} N$ with $g_{ ext{η'} NN^*}^2/4 ext{π} = 1.1$

Abstract

We study the near-threshold $\eta '$ production mechanism in nucleon-nucleon and $\pi N$ collisions under the assumption that sub-threshold resonance $N^{*}(1535)$ is predominant. In an effective Lagrangian approach which gives a reasonable description to the $pN \to pN \eta$ and $\pi p \to p \eta$ reactions, it is found that t-channel $\pi$ exchange make the dominate contribution to the $pN \to pN \eta '$ process, and a value of 6.5 for the ratio of $\sigma (pn \to pn \eta ')$ to $\sigma (pp \to pp \eta ')$ is predicted. A strong coupling strength of $N^{*}(1535)$ to $\eta ' N$ ($g_{\eta ' NN^*}^2 /4\pi = 1.1$) is extracted from a combined analysis to $pp \to pp \eta '$ and $\pi N \to N \eta '$, and the possible implication to the intrinsic component of $N^{*}(1535)$ is explored.