Isospin dependence of the eta-prime meson production in collisions of nucleons

TL;DR

This study measures the upper limit of eta-prime meson production in proton-neutron collisions near threshold energies, providing insights into its production mechanisms and ruling out certain resonance contributions.

Contribution

It presents the first upper limit measurements of the eta-prime production cross section ratio in nucleon collisions near threshold energies, challenging the dominance of the S11(1535) resonance.

Findings

The ratio R(eta-prime) is smaller than that for eta meson.

The data exclude S11(1535) resonance as the main production mechanism.

Results suggest possible glue or mesonic current contributions.

Abstract

The upper limit of the total cross section for quasi-free pn -> pn eta-prime reaction has been determined in the excess energy range near the kinematic threshold. The measurement has been carried out at the COSY-11 detection setup using a proton beam and a deuteron cluster target. The identification of the eta-prime meson has been performed using the missing mass technique. The energy dependence of the upper limit of the cross section is extracted with a fixed proton beam momentum of p_beam}=3.35GeV/c and exploiting the Fermi momenta of nucleons inside the deuteron. The data cover a range of centre-of-mass excess energies from 0 to 24 MeV. The experimentally determined upper limit of the ratio R(eta-prime)=sigma(pn -> pn eta-prime) sigma(pp -> pp eta-prime), which is smaller than the ratio for the eta meson, excludes the excitation of the S_11(1535) resonance as a dominant production mechanism of the eta-prime meson in nucleon-nucleon collisions. At the same time, the determined upper limits of R(eta-prime) go in the direction of what one would expect in the glue production and production via mesonic currents. For quantitative tests of these mechanisms an order of magnitude larger statistics and a larger energy range would be required. This can be reached with the WASA-at-COSY facility.