Variational calculations of resonant states in 4He

We present a modified R-matrix method which allows microscopic calculations of nucleon-nucleus scattering at low energies. This method may be applied in conjunction with any of the commonly used methods for the ground states of few-body systems, i.e. the Green function Monte Carlo, Faddeev and variational techniques. We then report results of variational calculations of low-energy tp scattering in the region of 0⁺, 0^? and 2^? resonances in ⁴He. The energies and widths of these resonances are calculated using realistic two- and three-nucleon interactions; but, the Coulomb interaction is neglected. The three-nucleon interaction is found to have a much smaller effect on the energies of the resonances than on the ground-state energy.