A Theoretical Study of ${\rho }^0$-Photoproduction on Nucleons near Threshold

Abstract

We investigate the possibility that the process of ${\rho }^0$-meson photoproduction on proton, $\gamma +p\to p+{\rho }^0$, in the near threshold region $E_{\gamma }<2$ GeV, can be considered in the framework of model with $\pi$-, $\sigma$- and N-exchanges. This suggestion is based on a study of the t-dependence of differential cross section, $d\sigma (\gamma p\to p{\rho }^0)/dt$, which has been measured by SAPHIR Collaboration. We find that the suggested model provides a good description of the experimental data with new values of $\rho NN$-coupling constants in the region of the time-like ${\rho }^0$-meson momentum. Our results suggest that such model can be considered as a suitable nonresonant background mechanism for the future discussion of possible role of nucleon resonance contributions. Our predictions for ${\rho }^0$-meson photoproduction on neutron target and for beam asymmetry on both proton and neutron targets are presented.

Comments: 21 pages, RevTex, 6 PS figures