Nondiffractive feature of $\gamma N\to \rho^\pm N$ with $\rho$-meson electromagnetic multipole moments

TL;DR

This paper studies charged rho meson photoproduction off nucleons, emphasizing the role of electromagnetic multipole moments and Ward identity, and reproduces nondiffractive cross section features without model dependence.

Contribution

It introduces a model-independent analysis of rho meson photoproduction considering electromagnetic multipole moments and highlights the nondiffractive nature of the process.

Findings

Reproduces nondiffractive cross section behavior.

Predicts parity and photon polarization asymmetries.

Analyzes the role of electromagnetic multipole moments.

Abstract

We investigate photoproduction of charged $\rho$ off the nucleon using $\rho(770)+\pi(140)$ Regge pole exchanges by considering the $\rho$-meson electromagnetic multipole moments. The significance of the Ward identity at the $\gamma\rho\rho$ vertex is emphasized for current conservation in the process. Given $\pi$ exchange with the well-known coupling constants for $\gamma\pi\rho$ and $\pi NN$, we analyze the role of the $\rho$ exchange in the $\gamma p\to \rho^+n$ and $\gamma n\to\rho^-p$ processes without model-dependences except for the magnetic moment $\mu_{\rho^\pm}=\pm2.01$ and electric quadrupole moment ${\cal Q}_{\rho^\pm}=\pm0.027$ fm$^2$ taken from theoretical estimates. The nondiffractive feature of both cross sections is reproduced with a rapid decrease beyond the resonance region by the dominance of $\pi$ exchange over the $\rho$\,. % Cross sections for differential and density matrix elements are presented to compare with existing data. The parity and photon polarization asymmetries are predicted to demonstrate the apparent roles of the $\rho$-meson electromagnetic multipole moments.