Summing of ladder diagrams in the theory of the (d, p) stripping reactions at low energies

Validity of the Born approximation to the neutron capture into the single,particle 2s states of the middle 1p-shell nuclei is studied in the two coupled channel approximation at deuteron energies of several MeV. The nondiagonal potential is determined using the validity of the Born approximation at higher energies. The smallness parameters which characterize the validity of the Born approximation are introduced. Summing of ladder diagrams is found to be very essential (the smallness parameter β0 > or approximately 1) at rather low energies (of several MeV). However, it seems that the effect has been hidden up to now because it can be imitated in the framework of distorted wave method by variation of free parameters