Possibility of generating a 4-neutron resonance with a T=3/2 isospin 3-neutron force

We consider the theoretical possibility of generating a narrow resonance in the 4-neutron system as suggested by a recent experimental result. To that end, a phenomenological T=3/2 3-neutron force is introduced, in addition to a realistic NN interaction. We inquire what the strength should be of the 3n force to generate such a resonance. The reliability of the 3-neutron force in the T=3/2 channel is examined, by analyzing its consistency with the low-lying T=1 states of H4,He4, and Li4 and the H3+n scattering. The ab initio solution of the 4n Schrödinger equation is obtained using the complex scaling method with boundary conditions appropriate to the four-body resonances. We find that to generate narrow 4n resonant states a remarkably attractive 3N force in the T=3/2 channel is required.