Tatuya Sasakawa

Tensor Force of the Pion-Theoretical Potential and the Doublet Splitting in n-He4 Scattering

To investigate whether the spin-orbit force in the theory of nuclear shell structure is due to the tensor force of the pion-theoretical potential, the doublet splitting of the pphase shifts in low energy n-He/sup 4/ scattering was analyzed. It is concluded that the major pant of the experimental doublet splitting can be reproduced by the strong tensor force of the pion-theoretical potential. It is shown qualitatively which features of the pton-theoretical potential are important to the binding energy of He/sup 4/ and the discontinuity of the binding energies between He/sup 4/ and the system of He/sup 4/ plus one nucleon. (auth)

High Energy Elastic Scattering of Nucleon from Nuclei : Analyses of Experimental Data

In the previous paper by one of the authors (T. S.) /J in the assumption that the short-range correlation between nucleons and the Pauli principle in the target nucleus in its ground state plays an essential role in the high energy elastic scattering of nucleon from heavy nuclei, the following are predicted for the angular distributions: (1) The positions of maxima and minima coincide respectively with those given by the impulse approximation, (2) the absolute value of the angular distribution is multiplied by a constant factor I A 1 to that given by the impulse approximation, (3) this factor is an independent constant of mass number in heavy nuclei and independent of the incident energy, and finally ( 4) the magnitude of v1Xl 2 is order 0.4,.....,0.5. This factor results from the Pauli principle in the target nucleus. There, using the set of phase shifts based on the phenomenological inner potential with the one-pion-exchange tail,J, J the above predictions have been confirmed at 95Mev. In the present paper, we shall report the results of analyses at energies 95 Mev, 135 Mev, 310 Mev, and 340 Mev. Because, based on such a potential, the analyses of the two-body scattering have not been extended to higher energies, here we shall adopt the phase shifts by Gammel and ThalerJ listed in the paper by Kerman, McManus and Thaler.>

High Energy n-He^4 Scattering

Utilizing the impulse approximation, the differential cross section and the polarization for n-He⁴ elastic scattering at 90 Mev were calculated. The effect of the D-state was neglected, resulting in a discrepancy between the calculations and experimental results. (C.J.G.)

ELASTIC SCATTERING IN HIGH ENERGY AND IMPULSE APPROXIMATION

The increasing knowledge of n-p and p-p scattering has made it possible to get an insight into elementary scattering in the energy region up to 310 Mev phenome nologically and up to about 150 Mev theoretically. As a result it has been possible to choose a few sets of phase shifts concerning elementary scatterings. It is possible to make use of these results in applying the impulse approximation to estimate high-energy scatterings. (A.C.)

Spontaneous Fission Half-lives

A dynamical theory of nuclear distortion leading fission, is presented. This theory is based on_ the unified model (the collective model). But, since the spontaneous fission is, so to speak, an irreversible process, the present theory is treated reflecting this speciality. Starting from this dynamical theory, a semi-empirical formula of spontaneous fission half.lives of even-even nuclei is derived. This formula can well reproduce the general tendency of spontaneous fission half-lives of even-even nuclei. The essential features which affect half-lives are discussed. Finally, a reasoning for the asymmetry character of fission and the orientation in calculating the difference of half-lives between even-even and even-odd nuclei are given.

Symmetry Property of the S Matrix on the Basis of the Jost Function Method

Under the assumption that the spinless particle of s wave is scattered by the spinless target with an arbitrary enumerative number of discrete excited states, this paper derives all symmetry relations on the basis of the J ost function method for any number of open and closed channels. This method explicitly describes the symmetric structure of the S matrix from which the symmetry properties originate. As an application of the method, the threshold behavior is also discussed without employing the channel radius.

Self-Bound Finite System

Starting from the N (2 2)-body system, formulas for calculating the bound state energy and the wave functions of any M(>N) -body system is given in a compact form. By employing this method, we can obtain all the correct information about any system consisting of many particles. It is, of course, especially suited for solving a-few-body problems. Two aspects of this method should be emphasized: Firstly, one can deal with the scattering problem and the bound state problem on the same basis. Secondly, this treatment leaves no ambiguity about the freedom of the center of mass motion of the total system. The approximation which leads to the single particle model is discussed. The effective single particle potential is derived under the liN-approximation for the strong coupling limit. It takes a form which is similar to the effective single particle potential appeared in the theory of infinite matter.

Converging Scattering Theory and Its Application

A method is described for potential scattering in which the asymptotic wave inside the scatterer is taken as a zero-order function in the iteration procedure. The scattering amplitude is determined self-consistently.

Meson Theoretical Potential and Nuclear Properties

The relationship of the meson potential to nuclear properties is derived with reference to the hard (repulsive) core. The nucleus is assumed to contain equal numbers of neutrons and protons, of which the part having spin up is equal to that having spin down, so that tensor forces do not contribute to the binding energy in first order. A hard core is shown to exist inside the main attractive pant of the potential, which means that the one-pionexchange is insignificant in the nuclear saturation. However, the surface contribution to the energy comes mainly from this exchange. (D.L.C.)

A Note on Exchange Reaction

The quasi-elastic scattering reaction (p,p), and the charge exchange reactions (p,n) and (n,p) are considered. A theory for the scattering amplitudes for these reactions is analyzed, in which the scattering amplitude is expressed as the square root of the sticking factor times the dynamicel factor. The scattering matrtx elements iovolving the incident and ejected particles are given in the impulse approximation for the above reactions. The dynamical factors of the marix elements for elastic scattering and change exchange are found to differ. On the basis of this difference, it is found that the proposed theory is applicable only to inelastic scattering reactions (p,p). (T.F.H.)