|Budget Amount *help
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
We have studied the structure and fragmentation of s-hole states in light nuclei, which are related closely to the study of hypernuclei and the measurement of nucleon lifetime etc.
・ SU(3) model for s-hole states and a selection rule
We proposed the SU(3) model for s-hole states in light nuclei. This model is based on the fact that the s-hole state produced by the quasifree knockout reactions such as a ィイD1AィエD1Z(p, 2p) should have the same spatial symmetry as the ground state of the target nucleus, and the ground-state wave function of light nuclei is described well by the SU(3) nuclear wave function. The main results are given as follows : 1) The doorway-stage fragmentation process of the s-hole state in light nuclei is superior or competitive to the compound-stage one. 2) A selection rule is found for fragmentation of doorway s-hole states in light nuclei ; in the two-body fragmentation process of the doorway s-hole states, smaller fragments than the α particle are allowed, while the
fragments such as the α particle and the larger particles are suppressed, in spite of the large Q value for the α fragment.
・ Experiments on the fragmentation of ィイD111ィエD1B(s-hole) and ィイD115ィエD1N(s-hole) produced by the EィイD2pィエD2 = 392 MeV ィイD112ィエD1C, ィイD116ィエD1O(p, 2p) reactions at RCNP, Osaka University
The two experiments were performed at RCNP (E81 and E110), and their analyses have been in progress now. The major results are given as follows. 1) The α fragmentation from the ィイD111ィエD1B(s-hole) and ィイD115ィエD1N(s-hole) states is found to be suppressed in comparison with the p, d and t ones, in spite of the large Q value of the α channel. This result is consistent with our prediction, and is not able to be explained with only the statistical model. 2) The s-hole state of ィイD111ィエD1B splits into three components to show the bump structure in the excitation spectrum of ィイD111ィエD1B. The three bumps have different branchingratios for p-, d-, t- and α-fragments.
・ ィイD112ィエD1C(p, 2p) excitation function with the 1hΩ shell model
In order to study the origin of the bump structure, we analyzed the ィイD112ィエD1C(p, 2p) excitation function with the 1hΩ shell-model wave function. Reflecting the spatial symmetry of the target nucleus ィイD112ィエD1C with the main (second main) SU(3)[f](λμ) component (04) (((12)), three SU(3) basis states of ィイD111ィエD1B, (04), (04), (12), are found to play an important role to produce the bump structure. This result indicated that the formation of the structure of the s-hole state in the ィイD1AィエD1Z(p, 2p) excitation function is attributed to the spatial symmetry of the target nucleus. This is due to the characteristic of the quasifree knockout reaction. Less