f2, σ, and 2π exchanges in ρ meson photoproduction

The sigma meson exchange model for rho photoproduction at low energies is re-examined and a new model is developed by considering explicit two-pion exchange and the f(2) tensor meson exchange. The f(2) exchange model, which is motivated by the low energy proton-proton elastic scattering, is constructed by fully taking into account of the tensor structure of the f(2) meson interactions. Phenomenological informations together with tensor meson dominance and vector meson dominance assumptions are used to estimate the f(2) meson's coupling constants. For 2pi exchange, the loop terms including intermediate piN and omegaN channels are calculated using the coupling constants determined from the study of pion photoproduction. It is found that our model with f(2) and 2pi exchanges can successfully replace the commonly used sigma exchange model that suffers from the big uncertainty of the coupling constants. We found that the two models can be distinguished by examining the single and double spin asymmetries.