Backward-angle photoproduction of $\omega$ and $\eta'$ mesons from protons at $E_{\gamma}=1.5-3.0$ GeV

TL;DR

This study measures differential cross sections for $$ and $'$ meson photoproduction from protons at backward angles using polarized photons in the 1.5-3.0 GeV range, revealing deviations from predictions and a notable bump at 2.35 GeV.

Contribution

First measurement of backward-angle photoproduction cross sections for $$ and $'$ mesons at these energies, highlighting discrepancies with theoretical models and identifying a resonance-like structure.

Findings

$$ cross sections exceed $u$-channel predictions between 2.0 and 2.4 GeV.

Cross sections approach $u$-channel predictions above 2.4 GeV.

A bump at $\u2212$2.35 GeV suggests possible resonance or new phenomena.

Abstract

We report the measurement of differential cross sections for $\omega$ and $\eta'$ photoproduction from protons at backward angles ($-1.0<\cos\Theta_{C.M}^{X}<-0.8$) using linearly polarized photons at $E_{\gamma}=$$1.5-3.0$ GeV. Differential cross sections for $\omega$ mesons are larger than the predicted $u$-channel contribution in the energy range $2.0\leq\sqrt{s}\leq2.4$ GeV. The differential cross sections for $\omega$ and $\eta'$ mesons become closer to the predicted $u$-channel contribution at $\sqrt{s}>2.4$ GeV. A bump structure in the $\sqrt{s}$ dependence of the differential cross sections for $\eta'$ mesons was observed at $\sqrt{s}\sim$2.35 GeV.