2002 Fiscal Year Final Research Report Summary
Study for nuclear media effect on chiral symmetry restoration
| Project/Area Number |
12440064
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | RIKEN (2001-2002)
Kyoto University (2000) |
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Principal Investigator |
EN'YO Hideto RIKEN, Radiation Laboratory, Chief Scientist, 放射線研究室, 主任研究員 (30213606)
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| Co-Investigator(Kenkyū-buntansha) |
MURAKAMI Tetsuya Kyoto University, Department of Physics, Research Associate, 理学研究科・物理学宇宙物理学専攻, 助手 (50219896)
TABARU Tsuguchika RIKEN, Radiation Laboratory, Contract Researcher, 放射線研究室, 協力研究員
YOKKAICHI Satoshi RIKEN, Radiation Laboratory, Special Doctoral Fellow, 放射線研究室, 基礎科学特別研究員
CHIBA Junsei High Energy Accelerator research Organization, IPNS, Associate Professor, 理学研究科・物理学宇宙物理学専攻, 助教授 (50126124)
FUNAHASHI Haruhiko Kyoto University, Department of Physics, Research Associate, 素核研, 助手 (00283581)
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| Project Period (FY) |
2000 – 2002
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| Keywords | phi meson / chiral symmetry / nuclear matter / media effect / invariant mass / electron pair |
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| Research Abstract |
It is believed that chiral symmetry, which is spontaneously broken in our world, should be restored in a system with a finite temperature and/or a finite density. Theoretically, it has been suggested that a signature of the chiral symmetry restoration could be seen as a possible mass shift of vector mesons in nuclear matter.
This research project has aimed the mass of ρ, ω and φ mesons produced, and decays in nuclei, through a determination of the invariant mass from the e^+e^- pairs, or the K^+K^- pairs following their decays. The experiment was successful to observe ω and φ mesons in the e^+e^- invariant mass spectra, and reported the signature of an in-medium mass modification of the mesons. This was the first observation in the leptonic in-medium decay of vector mesons at a normal nuclear matter density. The experiment finished the data taking in March 2002, and the statistics is improved by factor 100 compared to the previous publication and the preliminary data have been reported in international conferences. In another half year, we expect to reach the final results.
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