Omega and Eta (Eta-prime) mesons from NN and ND collisions at intermediate energies

TL;DR

This paper models meson production in nucleon-nucleon and nucleon-deuteron collisions at intermediate energies, analyzing cross sections, angular distributions, and di-electron decays, with implications for experimental measurements of transition form factors.

Contribution

It provides a covariant effective meson-nucleon theory that accurately describes meson production and decay processes, including pseudo scalar and vector mesons, and discusses experimental access to transition form factors.

Findings

Good description of vector meson production cross sections and angular distributions.

Pseudo scalar production requires nucleon resonance inclusion.

Numerical results for di-electron decay channels relevant to experiments.

Abstract

The production of pseudo scalar, Eeta, Eta-prime, and vector, Omega, Rho, Phi, mesons in NN collisions at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. It is shown that a good description of cross sections and angular distributions, for vector meson production, can be accomplished by considering meson and nucleon currents only, while for pseudo scalar production an inclusion of nucleon resonances is needed. The di-electron production from subsequent Dalitz decay of the produced mesons, $\eta'\to \gamma \gamma^* \to\gamma e^+e^-$ and $\omega\to \pi\gamma^*\to \pi e^+e^-$ is also considered and numerical results are presented for intermediate energies and kinematics of possible experiments with HADES, CLAS and KEK-PS. We argue that the transition form factor $\omega\to \gamma^*\pi$ as well as $\eta'\to \gamma^*\gamma$ can be defined in a fairly model independent way and the feasibility of an experimental access to transition form factors is discussed.