Study of the effect of the tensor correlation on the alpha–alpha interaction in 8Be with the charge- and parity-projected Hartree–Fock method

We study the effect of the tensor correlation on the alpha–alpha interaction in 8Be using an alpha cluster model. We use the wave function of the alpha particle calculated with the charge- and parity-projected Hartree–Fock method, which can treat the effect of the tensor correlation. The expectation value of the potential energy from the tensor force in 8Be is almost twice of that in the alpha particle and the tensor correlation energy between two alpha particles is a few MeV. The energy surface as a function of the relative distance between two alpha particles becomes much steeper in an inner region by the inclusion of the tensor correlation in the wave function of the alpha particle. This is caused by the p-state mixing induced by the tensor force. By superposing the wave functions with different relative distances, the reasonable binding energy of 8Be is obtained.