2001 Fiscal Year Final Research Report Summary
Investigation of specific properties of Hyperon-Nucleon and Hyperon-Hyperon interactions appearing in hypernuclear phenomena
| Project/Area Number |
11640286
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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 | Tsuru University |
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Principal Investigator |
YAMAMOTO Yasuo Tsuru University, literature, professor, 文学部, 教授 (80124866)
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| Project Period (FY) |
1999 – 2001
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| Keywords | hypernucleus / ^(c) spin-orbit splitting / antisymmetric LS interaction / double-^(c) hypernucleus / hyperon mixing in neutron star |
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| Research Abstract |
The important motivation for our research project was that some interesting results of experiments were opened in the term of our project. The ^(c) splitting energies in ^(c) hypernuclei were determined very precisely by observing the γ-ray transitions from spin-doublet states ; 5/2^+_1 and 3/2^+_1 states of ^9_^(c)Be (BNL-E930) and 3/2^-_1 and 1/2^-_1 states of ^<13>_^(c)C (BNL-E929). Before these experiments, we predicted the theoretical values of ^(c) splitting energies of ^9_^(c)Be and ^<13>_^(c)C, which were derived from the various ^(c)N spinorbit interactions. In comparison with the experimental data, showing the very small values of splitting energies, we pointed out the possibility of the strong cancellation between LS and antisymmetric LS components indicated by the quark models of ^(c)N interactions.
The important results of experiments were reported on the interactions in S = -2 states. In the KEK-E373 experiment the clear event was found in emulsion, which was uniquely iden
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tified as ^6_<^(c)^(c)>He. The extracted value of the ^(c)^(c) binding energy indicates that the ^(c)^(c) attraction is considerably weaker than the old understanding. On the basis of this new situation, we investigated possible structures of light double-^(c) hypernuclei systematically using three- and four-body cluster models. Another information was obtained from the BNL-E906 experiment in which they measured the emission probability of a Ξparticle from a (K^-, K^+ reaction point. We showed that the important features of ΞN scattering cross sections and underlying ΞN interactions can be extracted from this experimental data.
The important problem of hyperon mixing in neutron star matter has been discussed since old times. The theoretical calculations, however, were not necessarily based on the realistic YN and YY interactions. In our research project we investigated the effects of hyperon mixing for the equation of state (EOS) of neutron star matter using the recent versions of YN and YY interactions. The resulting EOS was found to be too soft to sustain the observed neutron star mass. We introduced the extra three-body repulsion among baryons to resolve this crucial problem. Less
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Research Products
(22 results)
