Features of $\omega$ photoproduction off nucleon target at forward angles : Dominance of $\pi$ exchange with Regge cuts and scaling of differential cross sections

TL;DR

This paper models omega photoproduction off nucleons at forward angles using a Reggeized approach, emphasizing the dominance of pion exchange with Regge cuts and analyzing cross sections and scaling behaviors in comparison with experimental data.

Contribution

It introduces a Reggeized model including multiple exchanges and demonstrates the importance of pion exchange with Regge cuts in omega photoproduction at forward angles.

Findings

Pion exchange dominates at low energies with Regge cuts modulating its contribution.

Cross sections are well reproduced and scaled at high energies.

The model explains recent experimental data on gamma p and gamma n reactions.

Abstract

We investigate photoproduction of $\omega$ off a nucleon target $\gamma N\to\omega N$ by using a Reggeized model where $\pi(135)+\sigma(500)+f_1(1285)+f_2(1270)$+Pomeron exchanges are included in the $t$-channel for the reaction at forward angles. The reaction mechanism at low energy is featured by the dominance of the $\pi$ exchange with the absorptive cuts introduced to modulate the pion contribution to both $\gamma p\to \omega p$ and $\gamma n\to \omega n$ reactions. Necessity of $\sigma$ exchange is illustrated in the analysis of the cross section from natural parity exchanges. Cross sections for differential, total, and spin density matrix with beam polarization are reproduced and compared with existing data on $\gamma p\to \omega p$. Scaled differential cross sections of Jefferson Lab data on $\gamma p\to \omega p$ are investigated at the production angle $\theta=90^\circ$ with the nonlinear trajectories for a saturation. Differential and total cross sections for the $\gamma n\to\omega n$ reaction are analyzed to compare with recent experimental data at the CBELSA/TAPS Collaboration. An application to the $\gamma p\to\omega\Delta^+$ reaction is presented to demonstrate the significance of the $\pi$ exchange in the total and differential cross sections.