| Project/Area Number |
08044092
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Joint Research |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
SUMI Yoshio Hiroshima Univ.Dept.of Phys.Professor, 理学部, 教授 (20029490)
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| Co-Investigator(Kenkyū-buntansha) |
HANS Boggild コペンハーゲン大学, ニールス・ボーア研究所, 教授
FABJAN Chris CERN PPE Div.Senior Researcher, 主任研究員
SAKAGUCHI Atsushi Osaka Univ.Dept.Phys.Associate prof, 助教授 (70205730)
SUGITATE Toru Hiroshima Univ.Dept.Phys.Associate prof, 理学部, 助教授 (80144806)
MIYAMURA Osamu The same as above., 理学部, 教授 (80029511)
BOGGILD Hans NBI Copenhagen Univ.Professor
BOGGILD Hans コペンハーゲン大学, ニールス・ボーア研究所, 教授
永宮 正治 コロンビア大学, ネヴィス研究所, 教授
BOGGILD H. コペンハーゲン大学, ニールス・ボーア研究所, 教授
FABJAN Ch.W. ヨーロッパ合同原子核研究所, 主任研究員
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed (Fiscal Year 1997)
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| Budget Amount *help |
¥10,800,000 (Direct Cost: ¥10,800,000)
Fiscal Year 1997: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 1996: ¥5,300,000 (Direct Cost: ¥5,300,000)
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| Keywords | High-energy heavy-ion collisions / HBT effect / Multiparticle production / Quark gluon plasma / NA44 Collaboration / CERN-SPS / 高エネルギーハドロン物質 / クォークグルオンプラズマ |
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| Research Abstract |
By means of the NA44 focussing spectrometer at the CERN-SPS,we have carried out a high-precision measurement of one-and two-particie spectra of hadrons emitted from Pb+Pb collisions at 158 GeV per nucleon. AII of singles spectra for pions, kaons, protons and deuterons show a Boltzmann-like distribution in the transverse mass (mT) with hadron-mass dependent temperature parameter. The parameter is linear in hadron mass, thereby implying that the hadron source expands with an average velocity of 0.4 times the velocity of light and the hadron-freezeout temperature is about 140 MeV.From the observed particle ratios it is found that if a chemical equilibrium is attained, the chemical equilibrium temperature is about 170 MeV,being somewhat higher than the freezeout temperature, and the chemical potential for u and d quarks is about 70 MeV,whereas that for strange quark is nearly equal to 30 MeV.
HBT interferometry study has been carried out for two-particle spectra, giving three dimentional HBT radius parameters RL,RTO and RTS.Values of these parameters for the Pb+Pb are always larger than the corresponding ones in p+Pb at 450 GeV and S+Pb at 200 GeV per nucleon. These HBT radii show an approximate inverse-square-root scaling in mT, consistently with thermal hydrodynamical model. The multiplicity density dependence of the HBT radii for pions shows that the pion freezeout occurs when the source expands up to a state in which the energy density goes down to a constant value which is close to that of normal nucleus.
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