Pomeron, nucleon-resonance, and $(0^{+},0^{-},1^{+})$-meson contributions in $\varphi$-meson photoproduction

Abstract

We investigate the reaction mechanism of the $\varphi$-meson photoproduction off the proton target, i.e., $\gamma p\to \varphi p$, up to $\sqrt{s}=2.8$ GeV. For this purpose, we employ an effective Lagrangian approach in the tree-level Born approximation, and we employ various experimental and theoretical inputs. As a theoretical setup, the vectorlike Pomeron ($C=+1$) is taken into account as a parameterized two-gluon exchange contribution. We also consider $f_1(1285)$ axial-vector-meson, ($\pi ,\eta$) pseudoscalar-meson, and ($a_0,f_0$) scalar-meson exchanges in the $t$ channel, in addition to the experimentally confirmed nucleon resonances, such as $N^{\ast }(2000,5/2^{+})$ and $N^{\ast }(2300,1/2^{+})$, for the direct $\varphi$-meson radiations in the $s$ and $u$ channels. We provide numerical results for the total and differential cross sections as well as the spin-density matrices in the Gottfried-Jackson, Adair, and helicity frames. We observe that, together with the universally accepted pomeron contribution, the considered meson and nucleon-resonance contributions play significant roles in reproducing the experimental data for the forward and backward $\varphi$-meson scattering-angle regions, respectively, indicating the nontrivial interferences between mesonic and baryonic contributions.

Comments: 18 pages, 11 figures