Study of Quark Gluon Plasma by Heavy Ion Collision
Grant-in-Aid for Overseas Scientific Survey.
|Research Institution||Nagoya University|
NIWA Kimio School of Sciences, Nagoya Univ.Assoc.Prof., 理学部, 助教授 (60113445)
DAVIS D.H. ロンドン大学, 理学部, 教授
NATALI S. バリ大学, 理学部, 教授
RAMELLO L. トリノ大学, 理学部, 助教授
BARONI G. ローマ大学, 理学部, 教授
ROMANO G. ヨーロッパ原子核研究機構, 教授
丹生 潔 名古屋大学, 名誉教授 (50013363)
児玉 康一 愛知教育大学, 教育学部, 助手 (70211901)
中村 光廣 名古屋大学, 理学部, 助手 (90183889)
星野 香 名古屋大学, 理学部, 助手 (70022738)
D.H. DAVIS ロンドン大学理学部, 教授
S. NATALI バリ大学理学部, 教授
L. RAMELLO トリノ大学理学部, 助教授
G. BARONI ローマ大学理学部, 教授
G. ROMANO ヨーロッパ原子核研究機構, 教授
D.H. Davis Univ.College London Professor
S. Natali Bari Univ.Professor
L. Ramello Torino Univ.Res.Assoc.
G. Baroni Rome Univ.Professor
G. Romano European Organization of Nuclear Research Professor
NIU Kiyoshi Nagoya Univ.Professor
KODAMA Koichi Aichi Univ.of Education Res. Assoc.
HOSHINO Kaoru School of Science, Nagoya Univ.Res.Assoc.
NAKAMURA Mitsuhiro. School of Sciences, Nagoya Univ.Res.Assoc.
|Project Fiscal Year
1990 – 1992
Completed(Fiscal Year 1992)
|Keywords||Quark Gluon Plasma / Charm Particle / Nuclear Emulsion / Hybrid Experiment / Heavy Ion Interaction / チャーム粒子 / 原子核乾板 / クォーク・グルーオン・プラズマ / 重イオン核反応 / 複合実験装置 / チャ-ム粒子 / クォ-ク・グル-オン・プラズマ|
In this research work, production characteristics of charm particles in 200 A.GeV/c^<32>S - nucleus central interactions has been studied. A hybrid experimental apparatus of 2 layers of emulsion tape and electronic counters has been developed for this work and used successfully. This is a first time in the world when 2 layers of emulsion tape has been used successfully. Currently, central interactions of ultra relativistic nucleus is the best way to explore the state of quarks and gluons. We tried to explore such a state through production characteristics of charm charm quarks in that state.
200 A.GeV/c^<32>S beam accelerated at the CERN SPS was exposed to 100 mum thick target, Ag and Pb, to produce central interactions. AS a fraction of central interactions is only 10% of total, the ring counter was used to select central interactions effectively. PSD was used to measure beam position and a fiducial mark was printed on the emulsion tape to know the position of a selected interaction on
the emulsion tape. Specially developed PSD was used to increase radiation hardness. The exposure was performed in 1990 August and we succeeded to recored 2 X 10^4 central interactions. About 500 events with charm production are expected in this sample by extraporating our result in ^<16>O - nucleus central interactions.
In this experiment, charm decays between the target and the upstream emulsion tape are detected. About 400 charged secondary particles are produced in ^<32>S central interactions. It is not practical to examine all tracks if they are from decay vertecies because a lot of fake second vertecies due to the inaccuracy of measurement could be produced. Thus, as the decay daughters of charm particles has the impact parameter of the order of 100mum, reconstruction of decay vertecies is done only with tracks which have the impact parameter greater than the accuracy of the measurement. But, unfortunately, our ordinal micro scope stage could not be used because its accuracy of few micron was not enough to keep high detection efficiency of charm decays. Thus we developed much more accurate micro scope stage of about 0.3 mum accuracy for almost 1 year. The standard deviation of the impact parameter of tracks from the primary interaction is about 4 mum with this new microscope stage. Thus tracks with the impact parameter > 20 mum can be used to search decay vertecies. The efficiency to detect events with charm production is estimated to be 40 % in this case. It takes about 2.5 hours to finish 1 event with this stage.
Systematic analysis with 2 micro scope stage was continued for 1 year. About 600 central interactions were measured and 11 events with charm candidate were found. This means that the production cross section per nucleon - nucleon interaction in ^<32>S - nucleus central interactions is about 15 mub and no statistically significant deviation from the nucleon - nucleon interaction was seen up tp now. A technical paper on the PSD has already been published. A technical paper on the emulsion tape is now under preparation and will soon be submitted to the Nuclear Instuments and Methods. Physics results will be published when we correct 2 time more statistics. Technical Knowledge and experience we obtained in the development of the accurate stage is now being adoped to the D_S * gamma detection in E653 experiments etc. Less
Research Output (17results)