Kazuyuki Ogata

Continuum-discretized coupled-channels method for four-body nuclear breakup in {sup 6}He+{sup 12}C scattering

We propose a fully quantum-mechanical method of treating four-body nuclear breakup processes in scattering of a projectile consisting of three constituents, by extending the continuum-discretized coupled-channels method. The three-body continuum states of the projectile are discretized by diagonalizing the internal Hamiltonian of the projectile with the Gaussian basis functions. For {sup 6}He+{sup 12}C scattering at 18 and 229.8 MeV, the validity of the method is tested by convergence of the elastic and breakup cross sections with respect to increasing the number of the basis functions. Effects of the four-body breakup and the Borromean structure of {sup 6}He on the elastic and total reaction cross sections are discussed.

Coulomb breakup effects on the elastic cross section of He 6 + Bi 209 scattering near Coulomb barrier energies

We accurately analyze the {sup 6}He+{sup 209}Bi scattering at 19 and 22.5 MeV near the Coulomb barrier energy, using the continuum-discretized coupled-channels (CDCC) method based on the n+n+ {sup 4}He+{sup 209}Bi four-body model. The three-body breakup continuum of {sup 6}He is discretized by diagonalizing the internal Hamiltonian of {sup 6}He in a space spanned by the Gaussian basis functions. The calculated elastic and total reaction cross sections are in good agreement with the experimental data, whereas the CDCC calculation based on the dineutron model of {sup 6}He, that is, the {sup 2}n+ {sup 4}He+{sup 209}Bi three-body model, does not reproduce the data.

Determination of the structure of {31}ne by a fully microscopic framework.

We perform the first quantitative analysis of the reaction cross sections of {28-32}Ne by {12}C at 240  MeV/nucleon, using the double-folding model with the Melbourne g matrix and the deformed projectile density calculated by antisymmetrized molecular dynamics. To describe the tail of the last neutron of {31}Ne, we adopt the resonating group method combined with antisymmetrized molecular dynamics. The theoretical prediction excellently reproduces the measured cross sections of {28-32}Ne with no adjustable parameters. The ground state properties of {31}Ne, i.e., strong deformation and a halo structure with spin parity 3/2{-}, are clarified.

Quantum Three-Body Calculation of the Nonresonant Triple-α Reaction Rate at Low Temperatures

Triple-α reaction rate is re-evaluated by directly solving the three-body Schrodinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. An accurate de- scription of the α-α nonresonant states significantly quenches the Coulomb barrier between the first two α-particles and the third α-particle. Consequently, the α-α nonresonant contin- uum states below the resonance at 92.04 keV, i.e., the ground state of 8 Be, give a markedly larger contribution at low temperatures than that reported in previous studies. We show that Nomotos method for three-body nonresonant capture processes, which is adopted in the NACRE compilation and many other studies, is a crude approximation of the accurate quantum three-body model calculation. We find an increase in triple-α reaction rate by about 20 orders of magnitude around 10 7 K compared with the rate of NACRE. Subject Index: 240, 481

Determination of the Structure ofNe31by a Fully Microscopic Framework

We perform the first quantitative analysis of the reaction cross sections of {28-32}Ne by {12}C at 240  MeV/nucleon, using the double-folding model with the Melbourne g matrix and the deformed projectile density calculated by antisymmetrized molecular dynamics. To describe the tail of the last neutron of {31}Ne, we adopt the resonating group method combined with antisymmetrized molecular dynamics. The theoretical prediction excellently reproduces the measured cross sections of {28-32}Ne with no adjustable parameters. The ground state properties of {31}Ne, i.e., strong deformation and a halo structure with spin parity 3/2{-}, are clarified.

Semiclassical distorted-wave model analysis of the ({pi}{sup -},K{sup +}){sigma} formation inclusive spectrum

({pi}{sup -},K{sup +}) hyperon production inclusive spectra with p{sub {pi}}=1.2 GeV/c measured at KEK on {sup 12}C and {sup 28}Si are analyzed by the semiclassical distorted-wave model. Single-particle (s.p.) wave functions of the target nucleus are treated using Wigner transformation. This method is able to account for the energy and angular dependences of the elementary process in nuclear medium without introducing the factorization approximation frequently employed. Calculations of the ({pi}{sup +},K{sup +}){lambda} formation process, for which there is no free parameter because the {lambda} s.p. potential is known, demonstrate that the present model is useful to describe inclusive spectra. It is shown that to account for the experimental data of the {sigma}{sup -} formation spectra a repulsive {sigma}-nucleus potential is necessary whose magnitude is not so strong as around 100 MeV previously suggested.

Deformation of Ne isotopes in the region of the island of inversion

The deformation of Ne isotopes in the island-of-inversion region is determined by the doublefolding model with the Melbourne g-matrix and the density calculated by the antisymmetrized molecular dynamics (AMD). The double-folding model reproduces, with no adjustable parameter, the measured reaction cross sections for the scattering of Ne from C at 240MeV/nucleon. The quadrupole deformation thus determined is around 0.4 in the island-of-inversion region and Ne is a halo nuclei with large deformation. We propose the Woods-Saxon model with a suitably chosen parameterization set and the deformation given by the AMD calculation as a convenient way of simulating the density calculated directly by the AMD. The deformed Woods-Saxon model provides the density with the proper asymptotic form. The pairing effect is investigated, and the importance of the angular momentum projection for obtaining the large deformation in the island-of-inversion region is pointed out.

The continuum discretized coupled-channels method and its applications

This is a review on recent developments of the continuum discretized coupled-channels method (CDCC) and its applications to nuclear physics, cosmology and astrophysics, and nuclear engineering. The theoretical foundation of CDCC is shown, and a microscopic reaction theory for nucleus-nucleus scattering is constructed as an underlying theory of CDCC. CDCC is then extended to treat Coulomb breakup and four-body breakup. We also propose a new theory that makes CDCC applicable to inclusive reactions

Strength of the Σ Single-Particle Potential in Nuclei from Semiclassical Distorted Wave Model Analysis of the (π−,K+) Inclusive Spectrum

The semiclassical distorted wave model is developed to describe (π - , K + ) inclusive spectra related to Σ - formation measured at KEK with p π = 1.2 GeV/c. The shape and magnitude of the spectrum obtained with a 28 Si target are satisfactorily reproduced using a repulsive Σ-nucleus potential whose strength is of the order of 30-50 MeV. This strength is not as large as the value of more than 100 MeV obtained using the estimation presented in the report of the experiment.

Deformation Effect on Total Reaction Cross Sections for Neutron-Rich Ne-Isotopes

The isotope dependence of measured reaction cross sections in the scattering of {sup 28-32}Ne isotopes from a {sup 12}C target at 240 MeV/nucleon is analyzed by the double-folding model with the Melbourne g matrix. The density of the projectile is calculated by the mean-field model with the deformed Woods-Saxon potential. The deformation is evaluated by antisymmetrized molecular dynamics. The deformation of the projectile enhances calculated reaction cross sections to the measured values.