Backward-angle electroproduction of $\eta'$ mesons off protons at $W=2.13~\text{GeV}$ and $Q^{2}=0.46~\left(\text{GeV}/c\right)^{2}$

TL;DR

This study measures the electroproduction cross section of $ ext{eta'}$ mesons off protons at specific energy and momentum transfer, validating a theoretical model and constraining resonance coupling strengths.

Contribution

First experimental measurement of $ ext{eta'}$ electroproduction at backward angles at $W=2.13$ GeV, providing data to test and refine isobar models.

Findings

Measured differential cross section: 4.4 ± 0.8 (stat.) ± 0.4 (sys.) nb/sr.

Cross section is one-sixth of real-photoproduction at backward angles.

Model comparison constrains coupling between $ ext{eta'}p$ final state and nucleon resonances.

Abstract

The electroproduction of $\eta '$ mesons from a $\mathrm{^{1}H}$ target at $W=2.13~\text{GeV}$, $Q^{2} = 0.46~\left( \text{GeV}/c\right)^{2}$ and $\cos \theta^{\text{CM}}_{\gamma^{*}\eta'} \approx -1$ has been experimentally measured. The differential cross section of virtual-photoproduction has been obtained as $4.4 \pm 0.8 ~\left( \text{stat.} \right) \pm 0.4 ~\left( \text{sys.} \right)~ \text{nb/sr}$ in the One-Photon-Exchange Approximation. This value is one-sixth of that of real-photoproduction at backward angles. A comparison with newly-developed isobar model calculations not only shows validity of the theoretical framewark employed, but also imposes new constrains on coupling strength between the $\eta'p$ final state and nucleon resonances.