Production of the omega meson in the pd --> 3He omega reaction at 1450 MeV and 1360 MeV

TL;DR

This study investigates omega meson production in proton-deuteron collisions near threshold energies, measuring angular distributions and cross sections, revealing discrepancies with existing theoretical models.

Contribution

It provides new experimental data on omega meson production at two energies and tests the validity of a two-step theoretical model.

Findings

Isotropic angular distribution at 1360 MeV

Forward and backward enhancements at 1450 MeV

Two-step model underestimates cross sections

Abstract

The production of $\omega$ mesons in the $pd \to{}^3$He$ \omega$ reaction has been studied at two energies near the kinematic threshold, $T_p=1450$ MeV and $T_p=1360$ MeV. The differential cross section was measured as a function of the $\omega$ cm angle at both energies over the whole angular range. Whereas the results at 1360 MeV are consistent with isotropy, strong rises are observed near both the forward and backward directions at 1450 MeV. Calculations made using a two-step model with an intermediate pion fail to reproduce the shapes of the measured angular distributions and also underestimate the total cross sections.