Relativistic effects in low-energy nucleon-nucleon scattering

We show that it is possible to obtain a quantitatively excellent description of low energy NN scattering, including the deuteron, using a relativistic equation with a simple one boson exchange kernel consisting of the exchange of only π,σ,ρ, and ω mesons. Relativistic properties of the meson-nucleon couplings play an essential role in the success of the description. A second model which includes ${\mathrm{\sigma }}_1$ and η mesons in addition to those in the four-meson model has also been constructed and is virtually equivalent to the four-meson model on shell. Since these two models differ off shell and are the same on shell, the low energy on-shell NN data cannot completely determine the off-shell NN amplitudes.