Yasunori Iseri

Continuum-discretized coupled-channels calculations for three-body models of deuteron-nucleus reactions

Abstract The formalism and results of truncated coupled channels evaluations of three-body models of deutron-induced nuclear reactions are reviewed. Emphasis is placed on breakup, elastic scattering and stripping. The relations of the coupled channels method to the Faddeev method, the adiabatic approximation and the distorted wave Born approximation are discussed extensively. Although the adiabatic approximation is seen to be excellent for the wavefunction in the elastic channel, it significantly underestimates the contributions of breakup states in stripping. Significant effects are associated with coupling to relative l = 2 breakup states.

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.

Virtual breakup effects in elastic scattering of polarized deuterons

Abstract Elastic scattering of polarized deuterons at Ed = 56 MeV is investigated for 16O, 40Ca, 58Ni, 118Sn and 208Pb target nuclei by the use of folding interactions. Effects of virtual breakup of the deuteron to S- and D-states in the continuum region are taken into account by the CDCC method and are found to make indispensable contributions to cross sections and analyzing powers, where continuum-continuum couplings are substantial. The contribution of the D-state admixture in the ground state is important for the tensor analyzing powers. The calculated results agree well with experimental data. The invariant-amplitude method and the second-order sum rule study clarify the characteristic feature of the spin dependence of the effective interactions due to the virtual breakup. The near-side/far-side decomposition of scattering amplitudes illuminates the difference of the reaction mechanism between light and heavy target nuclei. The investigation for the 208Pb target at Ed = 21.5 MeV gives important information on the energy dependence of the effective interactions. The use of different parameter sets for the input nucleon-target optical potentials shows that the detailed results depend significantly on the choice of the parameter sets.

A coupled-channel approach to deuteron projectile breakup

Abstract The proton-neutron coincidence cross section and proton spectrum in the (d, pn) reaction on 12 C, 51 V and 118 Sn at E d = 56 MeV are analyzed with the method of coupled discretized continuum channels based on the three-body model. The calculation reproduces well the experimental data. The strong coupling among the deuteron breakup channels and the validity of prior-form DWBA are discussed.

Determination of S 17 from B 8 breakup by means of the method of continuum-discretized coupled channels

The astrophysical factor for 7Be(p, γ)8B at zero energy, S17(0), is determined from an analysis of 208Pb(8B, p+7Be)208Pb at 52 MeV/nucleon by means of the method of continuum‐discretized coupled‐channels (CDCC) taking account of all nuclear and Coulomb breakup processes. The asymptotic normalization coefficient (ANC) method is used to extract S17(0) from the calculated breakup cross section. The main result of the present paper is S17(0) = 20.9−1.9+2.0 eV b. This value of S17(0) differs from the one extracted with the first‐order perturbation theory including Coulomb breakup by dipole transitions: 18.9 ± 1.8 eV b. It turns out that the difference is due to the inclusion of the nuclear and Coulomb‐quadrupole transitions and multi‐step processes of all‐order in the present work. Our main result of S17(0) is consistent with the value obtained from a precise measurement of the p‐capture reaction cross section extrapolated to zero incident energy, S17(0) = 22.1 ± 0.85 eV b. Thus, the agreement between the valu...

Gaussian expansion approach to nuclear and Coulomb breakup

We present an accurate method of simultaneously treating nuclear and Coulomb breakup of weakly bound nuclei by means of the method of continuum discretized coupled channels with the pseudostate method of discretization. As L{sup 2}-type basis functions of expansion of bound and continuum states of the projectile, we take complex-range Gaussian functions which in good approximation form a complete set in a large configuration space which is important for both nuclear- and Coulomb-breakup processes. The accuracy of the method is tested quantitatively for {sup 8}B+{sup 58}Ni scattering at 25.8 MeV.

Effects of tensor interaction in p-n breakup states on deuteron elastic scattering

Abstract The Reid soft core potential is employed for p-n continuum states in virtual-breakup components of deuteron elastic scattering. Compared to the previous calculation with central gaussian potentials, the new calculation produces small but non-negligible corrections to tensor analyzing powers and a remarkable change in a particular linear combination of polarization transfer coefficients, suggesting the latter to be a useful source of information on nuclear forces.

Coupled-channel approach to deuteron elastic scattering at intermediate energy

Abstract Deuteron elastic scattering at 400 MeV is analyzed with the coupled-channel method to treat the deuteron breakup process. Substantial improvement over the single-folding optical model is obtained in the fit to the experimental cross section. Wine-bottle shaped nucleon optical potentials are superior to Woods—Saxon ones for the deuteron scattering, while both types of potentials reproduce proton-scattering data equally well.

Spin-dependent interactions and polarization observables in elastic scattering of deuterons at intermediate energies

Abstract Deuteron-nucleus spin-dependent interactions are investigated in elastic scattering at intermediate energies. Spin-space tensor amplitudes which characterize spin-dependent interactions are introduced by the invariant-amplitude method so that effects of T R - and T L -type tensor interactions are described separately. Through these amplitudes, numerical calculations based on the folding model clarify that the spin-orbit interactions produce T L -tensor like effects on the scattering amplitude as the higher-order effect and the virtual breakup contribution is only a minor part of this effect in most angles. An additional T L -type tensor interaction, phenomenologically introduced, is found to improve the fit to the experimental data of A yy considerably and A y in less magnitude. The origin of this interaction is discussed. The theoretical prediction is made of which observables enhance the effect of a particular spin-dependent interaction.