| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1989: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
We predicted possible existence of the lightest sigma-hypernuclei, ^4_MAHe and ^4_MAH, based on microscopic calculations of NNNSIGMA four-body systems. In 1988 autumn, an experimental group of University of Tokyo succeeded in observing the hypernucleus ^4_MAHe by ^4He (stopped K^-, pi^-) reaction at KEK. This is only one existing-datum of the sigma-hypernuclear bound state. The binding energy and the width are in good agreement with our predicted values. We analyzed in detail the datum of ^4_MAHe, and revealed characteristic features of the nucleus-SIGMA interaction: Firstly, the nucleus-SIGMA potential has a repulsive core at short distances. The repulsive core makes the width of the hypernucleus much narrower than that estimated previously. Secondly, the potential has a strongly isospin-dependent term (Lane term). This term plays an important role to produce the bound state. The Lane term was experimentally confirmed to exist from spectra of the (stopped K^-, pi^-) and (stopped K^-, pi^+) reactions done at KEK by the group of University of Tokyo.
From the above features of the nucleus-SIGMA interaction we can speculate possible existence of second, third sigma-hypernuclei. Even in the case of heavy nucleus ^<208>Pb, we could expect bound states with narrow widths Coulomb-assisted hybrid states). An experiment to detect heavier sigma- hypernuclei is going to be planed at KEK.
Thus, our present investigation supported with Grant-in-Aid for Scientific Research (C) provided a starting point for the new research field, Sigma-hypernuclei, which will be developed in future under Japan liadron Project and Canada KAON Project.
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