Relativistic NN scattering calculations withΔdegrees of freedom

The Bethe-Salpeter equation for NN-$\mathrm{N}\Delta$ scattering is extended to include $\Delta \Delta$ states also. With the exception of ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$, the effects are small for $T=1\mathrm{}$ because of dominance by $\mathrm{N}\Delta$ isobaric states. For $T=0\mathrm{}$ the influence is accordingly larger. Also a quasipotential approximation to the Bethe-Salpeter equation is considered. Substantial differences are found. In particular, the quasipotential results are considerably more sensitive to the coupling parameters of the transition interaction. As a result a better fit to existing experimental phase shift parameters is obtained with the Bethe-Salpeter equation.