Hiroyuki Kanada

Microscopic study of the d + α scattering system with the multi-channel resonating-group method

Abstract Specific distortion effects of the deuteron and α-clusters in the d + α system are examined by requiring that the stability conditions for both clusters are satisfied. The results show that these effects for the deuteron cluster are very important; on the other hand, specific distortion for the α-cluster seems to have a rather minor influence. In this system, virtual-breakup effects of the deuteron are also examined within the framework of the multi-channel resonating-group method. It is noted that these effects are quite significant. Almost forbidden states which result from the coupling among various channels and spurious states which are caused by the choice of bound-state boundary conditions for excited channels are almost smeared out by introducing these effects. In addition, one notes that one can obtain a fairly good description of the experimental data on the 2 + excited states of 6 Li, the differential scattering cross section, and the vector and tensor polariz-ations. In this analysis, two types of nucleon-nucleon potential are adopted to examine the potential dependence of the calculated results. It is found that this kind of dependence is rather weak.

Characteristic features of specific distortion in light nuclear systems

Abstract The pseudo-state method is used to examine the specific distortion of the deuteron cluster in the channel spin- 3 2 state of the d + 3 He system. From the results obtained here and in previous investigations of many other light nuclear systems, we extract the characteristic features of specific distortion. These features are: (i) the importance of specific distortion is sensitively correlated with the cluster compressibility and the nucleon number of the companion cluster, (ii) specific distortion effects are both l - and energy-dependent, and (iii) specific distortion effects are much stronger in Pauli-favored l -states than in Pauli-unfavored l -states.

On Nucleon-He4 Interaction and Nuclear Forces

The nucleon-He/sup 4/ elastic scattering at the incident energies from 0 to 40 Mev is investigated in relation to the nuclear forces. The s-, p-, d-, and f-wave phase shifts are calculated by the nucleon-He/sup 4/ interaction, that is constructed from an approximated Hamada and Johnston nucleon-nucleon potential. The differential cross section and the polarization angular distribution calculated by these phase shifts are compared with the experimentai data. All essential features of the nucleon-He/sup 4/ scattering are explained in the energy region where the inelastic cross section is negligible. Especially the polarization at 40 Mev is fairly reproduced, which is attributed to very small (and negative) values of the d-wave phase shifts. The nucleon-He/sup 4/ interaction depends drastically on the energy and the state, as the result of the presence of large non-local interaction. The nucleon-He/sup 4/ spin-orbit coupling is constructed from the tensor and the spin-orbit part of the nucleon- nucleon forces. It is probable that the strength of the original spin-orbit force is rather weaker at low energies than that known from the high energy proton-proton scattering. (auth)

Spin-orbit potential in the Skyrme model

Abstract The full spin-orbit potential is calculated in the Skyrme model with a product ansatz. The magnitude of the potential agrees with conventional vector-meson exchange potentials in the asymptotic region. The isoscalar part has, however, the opposite sign to conventional potentials. This difficulty with the isoscalar part is similar to that of missing central attraction.

Multi-configuration resonating-group study of the three-nucleon system

The three-nucleon system is studied within the multi-configuration resonating-group method. The model space is spanned byp+d,p+d′, and their associated pseudo-inelastic configurations. The results show that, at lower energies less than about 15 MeV, the calculatedp+d differential scattering and total reaction cross sections agree well with experiment, suggesting that the use of pseudo-inelastic configurations can yield an adequate description of deuteron direct-breakup processes. At higher energies, the agreement is less satisfactory, owing mainly to the adoption of a relatively small number of pseudo-inelastic configurations in our formulation. Thep+d inter-cluster interactions are found to be appreciably odd-evenL-dependent and are characteristically different in channel spinS=3/2 and 1/2states. Specific distortion effects of the deuteron cluster are also studied. For relative orbital angular momentumL=0, these effects turn out to be small in theS=3/2 state but are quite large in theS=1/2 state.

Multi-configuration resonating-group study of the five-nucleon system

Abstract The properties of the five-nucleon system is investigated with a multi-configuration resonating-group method. The model space adopted is spanned by p + α, d + 3 He and deuteron pseudo-inelastic configurations. The results indicate that, with no adjustable parameters, the main characteristics of the p + α and d + 3 He differential scattering and reaction angular distributions can be reasonably well explained. Calculated total reaction cross sections in the p + α channel are found to be generally higher than experimental values, while the opposite is true in the d + 3 He channel. These latter findings are correlated with the observation that the general magnitudes of the calculated differential scattering cross sections in the p + α and d + 3 He channels are, respectively, smaller and larger than the measured results. Defects in the present model are also discussed, and a way to correct these defects is proposed.

Deformation Effect on the Skyrmion-(Anti-)Skyrmion Interaction Potential in the ω-Stabilized Skyrme Model

The Skyrme modeF) attracts interests both from the viewpoint of the effective lagrangian of the QeD and from the phenomenological aspect. A lot of efforts have been devoted to investigating the properties of oneand two-baryon systems by the original and generalized Skyrme models.)-9) In the course of the studies, it has been clarified) that the co-meson coupling term plays an important role in the model, and that the stabilization of the Skyrmion may depend strongly on the term. The static properties of the nucleon are known to be cosiderably improved by the model with the co-meson term, and the characteristic features of the nucleon-nucleon (NN) potential can also be fairly well reproduced by the model. One notes that the correct G-parity structure of the central potential is obtained by including the co-meson term. No improvement is, however, obtained for the medium-range attraction of the central potential; the resulting potential does not show any attraction necessary for the nuclear binding. Recently, it was shown that in the original Skyrme model the central potential is reduced by the amount of about 10 to 20% by taking into account a deformation effect of the Skyrmion.) The small amount of the reduction comes from the fact that the Skyrme term resists strongly such a deformation. On the other hand, Hajduk and Schwesinger ) showed that the co-meson term IS not influenced by the deformation of the Skyrmion. Then, it is very interesting to study to what extent the central potential in the Skyrmion-Skyrmion (SS) interaction is affected by the deformation of the Skyrmion in such a model, since the Skyrmion seems to be soft for the deformation. In this paper, we investigate such an effect on the central potential for the model of Adkins and N appi,4) where the Skyrmion is stabili~ed by the co-meson term instead of the so-called Skyrme term. There is so far no explicit calculation of the deformation effect on the Skyrmion-Skyrmion potential projected onto the central potential. The lagrangian adopted here is

Microscopic study of α+α bremsstrahlung with resonating-group wave functions

Bremsstrahlung double cross sections for α + α collisions are computed with the wave functions obtained by using a single-configuration resonating-group method (RGM). With no adjustable parameters, the calculated values are shown to agree well with experiment. For reliable results, it is found that the intercluster interaction must yield a good fit to the empirical phase shifts in the energy region where relatively sharp resonance states exist. A simplified procedure (A-RGM), in which the antisymmetrization of the wave function is only approximately taken into account, has also been adopted to consider the bremsstrahlung problem. Comparisons between RGM and A-RGM results yield the useful conclusion that fitting empirical phase shifts alone is not a sufficient criterion to ensure accuracy in the bremsstrahlung cross sections and a proper description of the nuclear system in the region of strong cluster overlap is also important.

Problems with the rotational collective coordinate method in the SU(3) Skyrme model of the baryon-baryon interaction

Abstract We calculate adiabatic baryon potentials in the SU (3) Skyrme model with the product ansatz, using the rotational collective coordinates based on the zero modes of SU (3)/U (1). While the potentials generally agree with conventional meson-exchange potentials in the asymptotic region, they are governed only by the pion mass scale and show peculiar disagreements generated by the chiral symmetry-breaking term.

Pion Form Factor and Possible Heavy Vector Meson

Recently, various properties have been known about the iso-vector part of electromagnetic form factors; as to the momentum dependence it is generally accepted that the nucleon form factor behaves as a dipole, while that of a pion is nearly a simple pole with p-meson dominance.1> The momentum dependence of the nucleon form factors can most naturally be explained by an accurate evaluation of the uncorrelated two-pion contribution as well as the correlated part corresponding to the p meson.2>-4> The pion electromagnetic form factor Fn (t), which was taken as an input in the above-mentioned computations,2> •4> is expressed in terms of the I =J = 1 denominator function D 1 <1> as follows: Fn(t)=D 1<1l(O)/D 1<1>(t). (1) For the D-function in the small t region, iti<1(GeV/c)2, the p-wave solution of the N / D equation for pion-pion scattering is used.5> As is shown in Fig. 1, Eq. (1) leads us to the result that is very close to the single p-meson dominance; the form factor, thus obtained, agrees qualitatively with the recent experimental pion form factor.6> In order to discuss the nucleon form factor Yn the whole space-like range of existing data, it is necessary to take on the contribution from .,!t =1.3-1.7 and/or 2.4 GeV energy regions.4> In such a higher mass region we have no confirmation of a vector meson with 1°=1 + although there are several indirect experimental reports.7l