2006 Fiscal Year Final Research Report Summary
Study of Hadron Properties in QCD with Finite Temperature and/or Density.
| Project/Area Number |
15340072
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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 |
Particle/Nuclear/Cosmic ray/Astro physics
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
OKA Makoto Tokyo Institute of Technology, Department of Physics, Professor, 大学院理工学研究科, 教授 (60144606)
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| Co-Investigator(Kenkyū-buntansha) |
SUGANUMA Hideo Kyoto Univ., Dept. Physics, Associate Professor, 大学院理学研究科, 准教授 (10291452)
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| Project Period (FY) |
2003 – 2006
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| Keywords | strong interaction / quantum chromodynamics / quark / gluon / baryon / hadron / lattice QCD / chiral symmetry |
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| Research Abstract |
Quantum Chromodynamics (QCD) is confining color in low-temperature and low density and the vacuum is in the chiral-symmetry breaking phase. It is believed that when the temperature and/or density get higher, the vacuum goes through a phase transition to a new ground state where color is de-confined and chiral symmetry must be restored. Non-perturbative approaches to clarify the properties of the phase transition. At the first stage of this research project, a totally new exotic hadron, pentaquark, was discovered and much interest was paid in this new situation. Starting with this event, the subjects of exotic hadrons, their structure and production mechanism, as well as exotic multi-quark components of ordinary hadrons become hot. We have studied the exotic hadrons from the viewpoints of finite temperature and density QCD.
The main results of the research were itemized.
(1)Pentaquark and spectrum of the exotic hadrons in the QCD sum rule approach :
We performed the first analysis of the pentaquark mass and quantum numbers based on the QCD, using the QCD sum rule technique. We found that the positive-parity pentaquarks are not likely to be in the low-mass region. We also proposed a method which distinguish the components of different number of quarks in a hadron. We applied the method to scalar mesons as well as Lambda^* baryon and they contain major exotic components.
(2)Lattice QCD analysis of pentaquarks and exotic hadrons :
We have analyzed pentaquark spectrum in the quenched lattice QCD. In order to distinguish a resonance from continuum, we proposed a twisted-boundary prescription and confirmed its effectiveness.
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