Low energy n+t scattering and the NN forces

The Faddeev-Yakubovsky equations have been solved in configuration space fo r the four nucleon system. The n+t elastic cross section has been calculate d using several realistic interactions and a phenomenological three-nucleon force. Special attention is devoted to the description of the observed res onant structure at T-lab approximate to 4 MeV. In the present state of the calculations, the realistic NN interactions are unable to describe the ener gy 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 t he resonant peak remains. This failure contrasts with the results of a pure phenomenological model. The origin of this disagreement as well as the pos sible issues are discussed. (C) 1999 Elsevier Science B.V. All rights reser ved.