Photoproduction of $\eta$ mesons off the proton for $1.2 < E_\gamma < 4.7$ GeV using CLAS at Jefferson Laboratory

TL;DR

This paper reports new measurements of $ exteta$ meson photoproduction off protons at energies from 1.2 to 4.7 GeV, extending the data into the Regge regime and comparing results with theoretical models and previous experiments.

Contribution

It provides extended differential cross section data for $ exteta$ photoproduction, including at higher energies, and compares these with Regge-based theoretical models and prior experimental results.

Findings

Data extend into the Regge regime beyond nucleon resonances.

Results are consistent with previous CLAS measurements.

Data support dominance of $ ho$, $ extomega$ vector-meson exchange.

Abstract

Photoproduction cross sections are reported for the reaction $\gamma p\to p\eta$ using energy-tagged photons and the CLAS spectrometer at Jefferson Laboratory. The $\eta$ mesons are detected in their dominant charged decay mode, $\eta\to \pi^+\pi^-\pi^0$, and results on differential cross sections are presented for incident photon energies between 1.2 and 4.7 GeV. These new $\eta$ photoproduction data are consistent with earlier CLAS results but extend the energy range beyond the nucleon resonance region into the Regge regime. The normalized angular distributions are also compared with the experimental results from several other experiments, and with predictions of $\eta$ MAID\,2018 and the latest solution of the Bonn-Gatchina coupled-channel analysis. Differential cross sections $d\sigma/dt$ are presented for incident photon energies $E_\gamma > 2.9$ GeV ($W > 2.5$ GeV), and compared with predictions which are based on Regge trajectories exchange in the $t$-channel (Regge models). The data confirm the expected dominance of $\rho$, $\omega$ vector-meson exchange in an analysis by the Joint Physics Analysis Center.