N+ H 3, p+ He 3, p+ H 3, and n+ He 3 scattering with the hyperspherical harmonic method

The n+H3, p+He3, p+H3, and n+He3 elastic and charge exchange reactions at low energies are studied by means of the hyperspherical harmonic method. The considered nuclear Hamiltonians include modern two- A nd three-nucleon interactions, and in particular results are reported in case of chiral two-nucleon potentials, with and without the inclusion of chiral three-nucleon (3N) interactions. A detailed study of the convergence and numerical stability of the method is presented. We have found that the effect the 3N force is in general tiny except for p+H3 scattering below the opening of the n+He3 channel. In such a case, the effect of 3N forces is appreciable and a clear dependence on the cutoff used to regularize the high-momentum tail of the interactions is observed. Such a dependence is related to the presence of the poorly known sharp 0+ resonance, considered to be the first excited state of He4.