3-α model and 3-body force

The 3-alpha model of 12C-nucleus is investigated by using the 3-body Faddeev equation with the Pauli-correct separable alpha-alpha potential. In the low-lying energy spectra of 12C-nucleus, there are characteristic states which contain the shell-model-like states, cluster-states and negative parity states. We obtain aculate energy levels of cluster-states, but shell-model-like-states is over bound. By introducing several types of 3-body forces, we study the role of 3-body force in the composite particle system like 12C-nucleus. It is found that the symmetric or 2-Gaussian type is better to reproduce the energy level structure than the others. (author)