Pion vs. photon absorption on the deuteron

Using an NN → ΔN transition potential fixed by the reaction pp ↔ dπ+ a good agreement can be obtained also for the reaction γd → pn in the Δ region. Further it is seen that the πNΔ and ϱNΔ parameters of the widely used Bonn potential, fitting the NN sector, yield a transition potential too weak to reproduce the pion production or absorption cross section.