# Kazuhito MizuyamaDuy Tan University · Department of Natural Sciences

Kazuhito Mizuyama

Ph.D

Human life is also complex system. Let's enjoy the complex system (=life).

## About

42

Publications

1,569

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590

Citations

Citations since 2017

Introduction

**Skills and Expertise**

Additional affiliations

April 2018 - present

April 2018 - present

April 2014 - March 2017

Education

April 2004 - March 2007

April 2002 - March 2004

April 1997 - March 2001

## Publications

Publications (42)

The properties of the scattering solutions obtained as poles of the S and K matrices are analyzed in terms of pairing effects in the framework of the Hartree-Fock-Bogoliubov (HFB) Jost function. As a result of our analysis, we found the following: in order for the poles of the S matrix to form a resonance, there must be a pole of the K matrix nearb...

The Jost function method is extended within the framework of the RPA theory to find poles on the complex energy plane that exhibit complex RPA eigenenergies. Poles corresponding to the RPA excited states such as the giant resonance of $^{16}$O electric dipole excitations were successfully found on the complex energy plane. Although the giant resona...

In this study, we analyzed how the incident neutron current is affected by the pairing effect in neutron-nucleus scattering described within the framework of Hartree-Fock-Bogoliubov theory by performing numerical calculations in terms of current, vorticity, and circulation of the incident neutron current.We found that the pairing effect on the inci...

In this study, we analyzed how the incident neutron current is affected by the pairing effect in the neutron-nucleus scattering described within the framework of Hartree-Fock-Bogoliubov theory by performing numerical calculations in terms of current, vorticity, and circulation of the incident neutron current. We found that the pairing effect on the...

In this paper, we analyze the role of central (t0) and density-dependent (t3) terms of the effective Skyrme interaction on the imaginary part of the optical potential, angular distributions, and analyzing powers of the low-energy neutron elastic scattering on a series of doubly closed shell nuclei in the framework of self-consistent mean-field appr...

We analyze the properties of the scattering solutions obtained as the pole of the S- and K-matrix with the help of the Jost function framework and the Strum-Liouville theory within the Hartree-Fock-Bogoliubov(HFB) framework, and clarify the scattering solutions which can be defined as the physical state. We found that there are three types of the r...

The Jost function formalism is extended with use of the complex potential in this paper. We derive the Jost function by taking into account the dual state which is defined by the complex conjugate the complex Hamiltonian. By using the unitarity of the S-matrix which is defined by the Jost function, the optical theorem with the complex potential is...

By focusing on the asymmetric shape of cross section, we analyze pairing effect on the partial wave components of cross section for neutron elastic scattering off stable and unstable nuclei within the Hartree-Fock-Bogoliubov framework. Explicit expressions for Fano parameters qlj and εlj have been derived and pairing effects have been analyzed in t...

By focusing on the asymmetric shape of cross section, we analyze the pairing effect on the partial wave components of cross section for neutron elastic scattering off stable and unstable nuclei within the Hartree-Fock-Bogoliubov (HFB) framework. Explicit expressions for Fano parameters $q_{lj}$ and $\epsilon_{lj}$ have been derived and the pairing...

We formulate the Jost function formalism based on the Hartree-Fock-Bogoliubov (HFB) theory which has been used to represent the nature of nuclear superfluidity. By using the Jost function based on the HFB, the S-matrix for the neutron elastic scattering by the open-shell nucleus can be represented analytically. Adopting the Woods-Saxon potential, w...

Neutron total and capture cross sections of ²⁴³Am have been measured in Accurate Neutron Nucleus Reaction measurement Instrument at Materials and Life Science Experimental Facility of Japan Proton Accelerator Research Complex with a neutron time-of-flight (TOF) method. The neutron capture cross section in the energy region from 10 meV to 100 eV was...

We formulate the Jost function formalism based on the Hartree-Fock-Bogoliubov (HFB) theory which has been used to represent the nature of the superfluidity of nucleus. The Jost function based on the HFB can give the analytic representation of the S-matrix for the nucleon elastic scattering targeting on the open-shell nucleus taking into account the...

Neutron total and capture cross sections of ²⁴¹Am have been measured with a new data acquisition system and a new neutron transmission measurement system installed in Accurate Neutron Nucleus Reaction measurement Instrument at Materials and Life Science Experimental Facility of Japan Proton Accelerator Research Complex. The neutron total cross sect...

In order to analyze the experimental data measured by the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex/Materials and Life Science Experimental Facility (J-PARC/MLF), it is necessary to take into account the double-bunch structure of the neutron pulse and the energy resolution func...

The neutron capture cross section of 99Tc was measured using NaI(Tl) detectors of the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex (J-PARC) in the energy range from thermal to the keV energy region. Preliminary results were presented and compared with previous measurements and eva...

To improve accuracy of neutron nuclear data on minor actinides, a Japanese nuclear data project entitled “Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)” has been implemented. Several independent measurement techniques were developed for improving measurement precision at J-PARC/MLF/ANNRI and KU...

There is large discrepancy among the reported experimental data of the thermal neutron capture cross section of 241Am, where the activation measurements provided larger cross sections than those in the time-of-flight ones. The Westcott convention has been widely used for the derivation of the thermal neutron capture cross section in the activation...

Some recent activities with the microscopic effective reaction theory (MERT) on elastic, inelastic, breakup, transfer, and knockout processes are reviewed briefly. As a possible alternative to MERT, a description of elastic and inelastic scattering with the continuum particle-vibration coupling (cPVC) method is also discussed.

Improvement of accuracy of neutron nuclear data for minor actinides (MAs) and long-lived fission products (LLFPs) is required for developing innovative nuclear system transmuting these nuclei. In order to meet the requirement, the project entitled as “Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMA...

Although self-consistent mean-field methods, or implementations of the density functional theory for atomic nuclei, are becoming increasingly accurate, some observables are not well reproduced by those models. In particular, the fragmentation and the decay properties of both single-particle and vibrational states cannot be accounted for. Models bas...

The proton inelastic scattering of $^{24}$O($p,p'$) at 62 MeV/nucleon is
described by a self-consistent microscopic calculation with the continuum
particle-vibration coupling (cPVC) method. The SLy5, SkM*, and SGII parameters
are adopted as an effective nucleon-nucleon interaction. For all the
parameters, the cPVC calculation reproduces very well t...

The presence of some low-lying (pygmy) strength in the dipole spectrum,
at excitation energy well below the isovector giant dipole energy, has
been confirmed in several nuclei. The microscopic structure and the
nature of these states, in particular the possible collective nature and
the isospin character, are currently under strong debate. In addit...

The microscopic description of neutron scattering by $^{16}$O below 30 MeV is
carried out by means of the continuum particle-vibration coupling (cPVC) method
with the Skyrme nucleon-nucleon ($NN$) effective interaction. In the cPVC
method, a proper boundary condition on a nucleon in continuum states is
imposed, which enables one to evaluate the tra...

We review some of the recent progress made in the particle-vibration
coupling calculations based on microscopic effective interactions. In
particular, we focus on the s.p. states and we also briefly discuss the
spreading width and decay modes of the giant resonances within the same
framework.

In this paper we present a new formalism to implement the nuclear
particle-vibration coupling (PVC) model. The key issue is the proper treatment
of the continuum, that is allowed by the coordinate space representation. Our
formalism, based on the use of zero-range interactions like the Skyrme forces,
is microscopic and fully self-consistent. We app...

The accurate characterization of the nuclear symmetry energy and its density dependence is one of the outstanding open problems in nuclear physics. A promising nuclear observable in order to constrain the density dependence of the symmetry energy at saturation is the neutron skin thickness of medium and heavy nuclei. Recently, a low-energy peak in...

The isospin character, the collective or single-particle nature, and the sensitivity to the slope of the nuclear symmetry energy of the low-energy isovector dipole response (known as pygmy dipole resonance) are nowadays under debate. In the present work we study, within the fully self-consistent nonrelativistic mean field (MF) approach based on Sky...

It is well known that within self-consistent random-phase approximation (RPA) on top of Hartree-Fock (HF), the translational symmetry should be restored. Because of approximations at the level of the practical implementation, this restoration may be only partial. As a result, one has spurious contributions in the physical quantities that are extrac...

We report on an implementation of a new method to calculate RPA strength functions with iterative non-hermitian Arnoldi diagonalization method, which does not explicitly calculate and store the RPA matrix. We discuss the treatment of spurious modes, numerical stability, and how the method scales as the used model space is enlarged. We perform the p...

The Gaussian expansion method (GEM) is extensively applied to the calculations in the random-phase approximation (RPA). We adopt the mass-independent basis-set that has been tested in the mean-field calculations. By comparing the RPA results with those obtained by several other available methods for Ca isotopes, using a density-dependent contact in...

We discuss the least-square and linear-regression methods, which are relevant for a reliable determination of good nuclear-mass-model parameter sets and their errors. In this perspective, we define exact and inaccurate models and point out differences in using the standard error analyses for them. As an illustration, we use simple analytic models f...

We show that single-particle energies in doubly magic nuclei depend almost linearly on the coupling constants of the nuclear energy density functional. Therefore, they can be very well characterized by the linear regression coefficients, which we calculate for the coupling constants of the standard Skyrme functional. We then use these regression co...

By means of the continuum QRPA calculations applied to excitation modes in medium and heavy mass neutron-rich nuclei we demonstrate that a surface di-neutron mode emerges as a fundamental mode of excitation in superfluid neutron-rich nuclei near the drip-line. We report also a recent development of the continuum QRPA theory in which the Skyrme ener...

We develop a new formulation of the continuum quasiparticle random phase
approximation (QRPA) in which the residual interaction is derived directly from
the Skyrme energy functional, keeping all the velocity dependent terms of the
Skyrme effective interaction. Numerical analysis using the SkM$^*$ parameter
set is performed for the isovector dipole...

We look for collective excitations originating from the strong surface pairing in unstable nuclei near the neutron drip-line. The soft dipole excitation is such a pairing mode as it exhibits a character of core-vs-dineutron motion. Possibility of the hydrodynamic phonon mode (the Anderson-Bogoliubov mode) is also discussed.

Investigating the pair correlation in medium-mass nuclei near the neutron drip-line, we find that the pairing involving several weakly bound neutrons exhibits a significant spatial correlation of the di-neutron type. We suggest that the strong spatial correlation is an inherent property of the pair correlation in nuclear matters at low densities. T...

On the basis of the coordinate-space Hartree-Fock-Bogoliubov and the continuum quasiparticle random phase approximation (QRPA) theories, we demonstrate that a di-neutron correlation exists in the ground states of medium-mass neutron-rich nuclei near the dripline, and we suggest that the soft dipole excitation has the character of di-neutron motion...

The neutron pairing correlation and the soft dipole excitation in medium mass nuclei near the drip line are investigated from the viewpoint of the di-neutron correlation. Numerical analyses based on the coordinate-space Hartree-Fock-Bogoliubov method and the continuum quasiparticle random phase approximation are performed for even-even 18-24O,50-58...

On the basis of the coordinate-space Hartree-Fock-Bogoliubov and the continuum quasiparticle random phase approximation (QRPA)
theories, we demonstrate that a di-neutron correlation exists in the ground states of medium-mass neutron-rich nuclei near
the dripline, and we suggest that the soft dipole excitation has the character of di-neutron motion...

It is well known that within self-consistent Random Phase Approximation (RPA) on top of Hartree-Fock (HF), the translational symmetry should be restored. Due to approximations at the level of the practical implementation, this restoration may be only partial. As a result, one has spurious contributions in the physical quantities that are extracted...

## Projects

Projects (2)

Fission barriers and optical potentials are two of the most important inputs for the nuclear reaction codes. In this work, these two inputs are microscopically generated from the effective nucleon-nucleon Skyrme interactions through the framework of self-consistent mean-field approaches and beyond. The obtained microscopic inputs are expected to be the useful tools for studying the nuclear structure and reactions in the region of unstable nuclei.