Ordinary “nuclear physics” had targeted naturally existing nuclei and had revealed the fundamental properties of nuclei and the dynamics of nuclear many-body systems through the investigation to the structures, reactions, and decays of “normal” nuclei. Recently, modern experimental facilities and supercomputer enable us to investigate new “exotic” nuclei. Especially, two large experimental facilities, “RIBF” and “J-PARC” have started working in Japan and with them, we can examine “unstable nuclei” and “hypernuclei” which do not exist stably on the earth. In our laboratory, we have tried to understand the subjects on nuclear physics, such as “quantum few- body problems”, “Origin of Atom”, and “the properties of baryonic matter and Neutron star” through theoretical and numerical analyses to “Unstable nucleai” and “Hypernuclei” which are experimentally studied in RIBF and J-PARC. Each topics will be presented as follows and if you want to know more, you can access our annual report (sorry but Japanese only).

### Unstable Nuclei and Cluster Structures

Because of strong correlation between nucleons, nuclei show various structures such as “cluster structure” which is characteristic to light nuclei. In recent studies about unstable nuclei, it has been suggested that nuclei lying around drip-line have far rich variations of structures since the correlations between nucleons emerge more drastically than normal nuclei. Thus, it becomes main-stream of unstable nuclear physics to investigate the structures of unstable nuclei and to aim to understand the properties of the correlation among many nucleons and the variation of structures. Now, we approach to these problems especially based on the viewpoint of the cluster structure.

*ab-initio* nuclear model calculation

In the cluster model study based on nuclear force, we try to explain the origin of this structure. We suggest that “Anti-symmetrized Molecular Dynamics (AMD)” is the only model which can include both shell-model-like structure drown by nuclear mean-field and cluster-model-like structure corresponding to the molecule-like picture. But now, we do not establish the effective interaction on a model space which has complicated state-dependency with the variation of nuclear structure. Thus, we aim to derive the effective interaction for AMD calculation from the realistic nuclear interaction based on Brueckner theory. Recently, we have tried to explain the emergence of cluster structure on ^{8}Be from the state-dependency of the nuclear tensor force and we have shown that the dependency of G-matrix to one-particle energy and the effect of Pauli principle yields α-α cluster structure. Now, based on this result, we compute α-α relative motion on Generating Coordinate Method

### Theoretical analysis of nuclear reaction process

It is very important to understand the nuclear reaction mechanism not only for knowing the information of the targeted nuclei’s structure, but also from the view of astrophysics, nucleosysthesis on astro-nuclear physics, and nuclear engineering. We investigate this subject with the framework of Continuum-Discretized Coupled-Channel (CDCC) which enables us to describe break-up process in detail, which is one of the important nuclear reaction process.

### Baryon many-body systems and Baroynic matter

Strangeness many-body systems, which is one of the phase of matter in nature, is not understood well. For example, the large number of hyperons, which has s quark as their constituent, appear in inner area of neutron star, but we cannot escape from the investigation about the properties of strangeness many-body systems for numerical discussion. On the other hand, hypernuclei where one or more hyperons are bound in core nuclei show the different properties compared to ordinal nuclei and thus, they are interesting subject to be examined its unique phenomena. Thus, we study these strangeness many-body systems such as hypernuclei and neutron star matter EOS theoretically based on the AMD and Relativistic Mean Field (RMF) and aim to understand the phase including s quark.