Upper limit of the total cross section for the pn --> pn eta' reaction

TL;DR

This study establishes an upper limit for the total cross section of the pn --> pn eta' reaction near threshold energies, providing insights into meson production mechanisms and resonance contributions.

Contribution

It presents the first measurement of the upper limit of the cross section for pn --> pn eta' near threshold, challenging the dominance of N*(1535) resonance in eta' production.

Findings

The upper limit of the cross section was determined near threshold energies.

The ratio R_eta' suggests different production mechanisms for eta and eta' mesons.

Results do not support N*(1535) resonance dominance in eta' production.

Abstract

The upper limit of the total cross section for the pn --> pn eta' reaction has been determined near the kinematical threshold in the excess energy range from 0 to 24 MeV. The measurement was performed using the COSY-11 detector setup, a deuteron cluster target, and the proton beam of COSY with a momentum of 3.35 GeV/c. The energy dependence of the upper limit of the cross section was extracted exploiting the Fermi momenta of nucleons inside the deuteron. Comparison of the determined upper limit of the ratio R_eta' = sigma(pn --> pn eta') / sigma(pp --> pp eta') with the corresponding ratio for eta-meson production does not favor the dominance of the N*(1535) resonance in the production process of the eta' meson and suggests nonidentical production mechanisms for eta and eta' mesons.