Role of tensor force in Be isotopes with tensor-optimized shell model

We investigate the role of tensor force in Be isotopes. We use the method of the tensor-optimized shell model, in which the strong tensor correlation is involved explicitly in the wave function by including the 2p2h excitations with high momentum. The short-range correlation is treated with central-UCOM. We employ the bare nucleon-nucleon force such as Argonne potential and examine how the bare tensor force determines the structures of Be isotopes such as the energy spectrum and the configuration mixing of the single-particle states. We investigate the tensor contribution of each energy level and clarify its relation to the important configurations of the single-particle states. We also discuss the alpha clustering correlation in neutron-rich Be isotopes on the basis of the two alpha-developed structure in 8Be.