Dynamical model of $ϕ$ meson photoproduction on the nucleon and $^4He$

Abstract

We investigate $ϕ$ meson photoproduction on the nucleon and the \nuclide[4]{He} targets within a dynamical model approach based on a Hamiltonian which describes the production mechanisms by the Pomeron-exchange, meson-exchanges, $ϕ$ radiations, and nucleon resonance excitations mechanisms. The final $ϕN$ interactions are included being described by the gluon-exchange, direct $ϕN$ couplings, and the box-diagrams arising from the couplings with $πN$, $ρN$, $KΛ$, and $KΣ$ channels. The parameters of the Hamiltonian are determined by the experimental data of $γp \to ϕp$ from the CLAS Collaboration. The resulting Hamiltonian is then used to predict the coherent $ϕ$-meson production on the \nuclide[4]{He} targets by using the distorted-wave impulse approximation. For the proton target, the final $ϕN$ rescattering effects, as required by the unitarity condition, are found to be very weak, which supports the earlier calculations in the literature. For the \nuclide[4]{He} targets, the predicted differential cross sections are in good agreement with the data obtained by the LEPS Collaboration. The role of each mechanism in this reaction is discussed and predictions for a wide range of scattering angles are presented, which can be tested in future experiments.