2002 Fiscal Year Final Research Report Summary
Effects of the instantons and quark degrees of freedom on properties of hypernuclei
| Project/Area Number |
11640258
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | Japan College of Social Work |
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Principal Investigator |
TAKEUCHI Sachiko Japan College of Social Work, Department of Social Work, Associate Professor, 社会福祉学部, 助教授 (90251503)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMIZU Kiyotaka Sophia University, Faculty of Science and Technology, Department of Physics, Professor, 理工学部, 教授 (00143363)
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| Project Period (FY) |
1999 – 2002
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| Keywords | hypernuclei / instanton / quark model / spin-orbit force / repulsive core / quark-pauli blocking / inverse scattering method / nonlocal potential |
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| Research Abstract |
We have investigated the effects of quark degrees of freedom on hypernuclei by employing the quark cluster model (QCM) with the instanton-induced interaction and/or π-and σ-exchange as well as the conventional one-gluon-exchange potential as two-quark interactions.
A realistic two-baryon potential which reproduces the known scattering observables was constructed from QCM. This QCM potential has a short range repulsion arising from the quark interaction and the middle and a long-range attraction coming from the one-boson exchange between the baryons. It is energy-independent and can be employed to investigate hypernuclei.
The QCM potential is nonlocal, because the original model has the internal degrees of freedom of baryons. We have evaluated the effects of its nonlocality. By using the inverse scattering method, the equivalent local potential which gives the same on-shell values as those of the original QCM potential was constructed. The G-matrices of the original and of the equivalent local potentials were compared to each other to investigate their off-shell properties. In the channels where the quark-Pauli-blocking effects are small, the G-matrices of the two potentials were found to be similar to each other; the equivalent local potential seems to simulate the QCM potential. On the other hand, in the channels where the quark-Pauli-blocking forbids most of the Os configuration, the G-matrix obtained from the equivalent nonlocal potential differs significantly from the original one at k>1.5fm^<-1>.
Moreover, when the correlation of quarks in the baryon is included in the configuration, the chiral quark model was found to reproduce the correct mass ordering of the positive and negative excited baryons. It was also found that suppose the mass difference between u-and d-constituent quarks is the same as that of current quarks, the short-range part of the charge symmetry breaking of the nuclear force can be explained quantitatively.
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