Takayuki Myo

The transition strength for Coulomb breakup of ${}^{6}\mathrm{He}$ into ${}^{4}\mathrm{He}+n+n$ three-body unbound states is studied in the framework of the complex scaling method (CSM). We propose a method to analyze the three-body unbound states in which CSM is utilized to decompose the three-body transition strengths into resonance and continuum components. We calculate the contributions of $E1$ and $E2$ transitions, not only from three-body resonances, but also from two-body ${\mathrm{``}}^{

We studied the roles of the tensor and pairing correlations on the halo formation in $^{11}\mathrm{Li}$ with an extended $^{9}\mathrm{Li}+n+n$ model. We first solved the ground state of $^{9}\mathrm{Li}$ in the shell-model basis by taking 2p-2h states using the Gaussian functions with variational size parameters to take into account the tensor correlation fully. In $^{11}\mathrm{Li}$, the tensor and pairing correlations in $^{9}\mathrm{Li}$ are Pauli blocked by additional two neutrons, which wor

It is shown that the strength function can be expressed as a sum of the contributions from bound, resonance and continuum terms and that the role of each term can be investigated complementarily by using the complex scaling method (CSM). The mechanism of the Coulomb breakup reaction of11 Be is analyzed, and we confirm the fact that the breakup is direct but not through resonances. The present method is also applied to other systems and its usefulness is discussed.

We investigate the role of tensor correlation on the structures of 4 He and its effect on the doublet splitting in 5 He. We perform a configuration mixing calculation in the shell model type bases to represent the tensor correlation for 4 He. It is found that our model describes the characteristics of the tensor correlation, which is represented by an admixture of the 0s 1/2 configuration with a spatially modified 0p 1/2 orbit. For 5 He, we solve a coupled OCM equation for an extended 4 He+n mod

We study the characteristics of the tensor correlation in 4He using a shell model type method. We treat the tensor force explicitly by performing a configuration-mixing calculation in the 2p2h basis and include single-particle states up to intermediately high angular momenta. We adopt the Gaussian expansion method for the quantitative description of the spatial shrinkage of the single-particle states to optimize the tensor correlation. We are able to describe the full strength of the tensor corr

We study the resonance spectroscopy of $^{7}\mathrm{He}$ in the $^{4}\mathrm{He}$$+n+n+n$ cluster model, where the motion of valence neutrons is described in the cluster orbital shell model. Many-body resonances are treated on the correct boundary condition as the Gamow states in the complex scaling method. We obtain five resonances and investigate their properties from the configurations. In particular, the $1/{2}^{\ensuremath{-}}$ state is found in a low excitation energy of 1.1 MeV with a wid

We studied the role of the tensor interaction in He isotopes systematically on the basis of the tensor-optimized shell model (TOSM). We use a bare nucleon-nucleon interaction AV8${}^{\ensuremath{'}}$ obtained from nucleon-nucleon scattering data. The short-range correlation is treated in the unitary correlation operator method (UCOM). Using the TOSM + UCOM approach, we investigate the role of tensor interaction on each spectrum in He isotopes. It is found that the tensor interaction enhances the

We develop a new formalism to treat nuclear many-body systems using the bare nucleon-nucleon interaction. It has become evident that the tensor interaction plays an important role in nuclear many-body systems due to the role of the pion in strongly interacting systems. We take the antisymmetrized molecular dynamics (AMD) as a basic framework and add a tensor correlation operator acting on the AMD wave function using the concept of the tensor-optimized shell model. We demonstrate a systematical a

We make a systematic study of Li isotopes (A=9,10,11) in the tensor optimized shell model for 9Li and treat the additional valence neutrons in the cluster model approach by taking into account the Pauli-blocking effect caused by the tensor and pairing correlations. We describe the tensor correlations in 9Li fully in the tensor-optimized shell model, where the variation of the size parameters of the single particle orbits is essential for getting strong tensor correlations. We have shown in our p

We study the tensor-optimized antisymmetrized molecular dynamics (TOAMD) as a successive variational method in many-body systems with strong interaction for nuclei. In TOAMD, the correlation functions for the tensor force and the short-range repulsion and their multiples are operated to the AMD state as the variational wave function. The total wave function is expressed as the sum of all the components and the variational space can be increased successively with the multiple correlation function

The 0+ states of 8He are studied in a five-body He4+n+n+n+n cluster model. Many-body resonances are treated on the correct boundary condition as Gamow states using the complex scaling method. The 02+ state of 8He is predicted as a five-body resonance in the excitation energy of 6.3 MeV with a width of 3.2 MeV, which mainly has a (p3/2)2(p1/2)2 configuration. In this state, number of the 0+ neuron pair shows almost two, which is different from the ground state having a large amount of the 2+ pair

We study the Li isotopes systematically in terms of the tensor-optimized shell model (TOSM) by using a bare nucleon-nucleon interaction as the AV8${}^{\ensuremath{'}}$ interaction. The short-range correlation is treated in the unitary correlation operator method (UCOM). Using the TOSM + UCOM approach, we investigate the role of the tensor force on each spectrum of the Li isotopes. It is found that the tensor force produces quite a characteristic effect on various states in each spectrum and thos

We investigate the binding mechanism of 11Li on the basis of an extended three-body model of 9Li+n+n. In the model, we take into account the pairing correlation of p-shell neutrons in 9Li, in addition to that of valence neutrons outside the 9Li nucleus, and solve the coupled-channel two- and three-body problems of 10Li and 11Li, respectively. The results show that the degrees of freedom of the pairing correlation in 9Li play an important role in the structure of 10Li and 11Li. In 10Li, the pairi

High-momentum components of nuclei are essential for understanding the underlying inter-nucleon correlations in nuclei. We perform the comprehensive analysis for the origin of the high-momentum components of 4He in the framework of Tensor-optimized High-momentum Antisymmetrized Molecular Dynamics (TO-HMAMD), which is a completely variational approach as an ab initio theory starting from the bare nucleon-nucleon interaction. The analytical derivations are provided for the nucleon momentum distrib