Low energy n+t scattering and the NN forces

The Faddeev-Yakubovsky equations have been solved in configuration space for the four nucleon system. The n+t elastic cross section has been calculated using several realistic interactions and a phenomenological three-nucleon force. Special attention is devoted to the description of the observed resonant structure at Tlab≈4 MeV. In the present state of the calculations, the realistic NN interactions are unable to describe the energy region considered, i.e. n+t S- and P-waves. Whereas the inclusion of a three-nucleon force improves the zero energy region, the disagreement in the resonant peak remains. This failure contrasts with the results of a pure phenomenological model. The origin of this disagreement as well as the possible issues are discussed.