Study of Quark Gluon Plasma by Heavy Ion Collision

重离子碰撞夸克胶子等离子体的研究

• 批准号: 02044066
• 负责人: NIWA Kimio
• 金额: $ 10.88万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 1992
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02044066/
• 关键词: Quark Gluon Plasma; Charm Particle; Nuclear Emulsion; Hybrid Experiment; Heavy Ion Interaction; 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 … More 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

在本研究工作中，研究了公元200年魅力粒子的生产特征。研究了GeV/c^<32>S -原子核中心相互作用。为此研制了一种由两层乳胶带和电子计数器组成的混合实验装置，并取得了成功。这是世界上第一次成功使用两层乳胶胶带。目前，超相对论核的中心相互作用是探索夸克和胶子状态的最好方法。我们试图通过生产这种状态下的粲夸克的特征来探索这种状态一个。在CERN SPS上加速的GeV/c^<32>S束流暴露于100 μ m厚靶Ag和Pb中，产生中心相互作用。由于中心相互作用仅占总相互作用的10%，因此使用环形计数器可以有效地选择中心相互作用。用PSD测量光束位置，并在乳化液带上打印基准标记，以确定选定的相互作用在乳化液带上的位置。采用特殊研制的PSD提高辐射硬度。暴露于1990年8月进行，我们成功地记录了2 × 10^4个中心相互作用。通过对^<16>O -核中心相互作用的结果进行外推，预计在该样本中约有500个具有粲子产生的事件。在本实验中，检测了目标与上游乳胶带之间的粲数衰减。在^<32>S中心相互作用中产生约400个带电二次粒子。由于测量精度不高，可能产生大量的伪二次点，因此对来自衰减顶点的轨迹进行检验是不现实的。因此，由于粲粒子的衰变子粒子的冲击参数为100mum数量级，因此只能使用冲击参数大于测量精度的轨迹来重建衰变顶点。但是，遗憾的是，我们的普通显微镜台由于其几微米的精度不足以保持高的粲衰变检测效率而无法使用。因此，我们在近1年的时间里研制出了精度更高的显微镜台，精度约为0.3 μ m。在这个新的显微镜阶段，轨迹的冲击参数与原始相互作用的标准差约为4 μ m。因此，具有冲击参数bbb20mum的轨迹可以用来搜索衰变顶点。在这种情况下，用符咒生成检测事件的效率估计为40%。在这个阶段完成一个事件大约需要2.5小时。2显微分期系统分析持续1年。测量了大约600个中心互动，发现了11个与魅力候选人有关的事件。这意味着^<32>S -核中心相互作用中每个核子-核子相互作用的产生截面约为15 mub，并且到目前为止还没有看到与核子-核子相互作用有统计学意义上的显著偏差。一篇关于PSD的技术论文已经发表。目前正在编写一份关于乳胶胶带的技术文件，不久将提交给核仪器和方法。物理结果将在修正2倍以上的数据后公布。我们在开发精确阶段中获得的技术知识和经验现在被应用于E653实验等中的D_S *伽马检测。少

项目成果

S. Aoki: "Charm Production by 350 Gec/c pi^-Interactions in Nuclear Emulsion" Prog. Theor. Phys.87. 1305-1313 (1992)

S. Aoki：“350 Gec/c pi^-核乳液中的相互作用产生魅力”Prog。

K. Kodama: "Measurement of the Branching ratio for D^+*K^*(892)ﾟmu^+nu" Physics Letters B. 286. 187-194 (1992)

K. Kodama：“D^+*K^*(892)ﾟmu^+nu 的分支比的测量”《物理快报》B. 286. 187-194 (1992)

T. Nakano: "Research and Development of Scintillating Fiber Tracker for nu*nu Oscillation Experiment" IEEE Transactions on Nuclear Science. 39. 680-684 (1992)

T. Nakano：“用于 nu*nu 振荡实验的闪烁光纤跟踪器的研究和开发”IEEE Transactions on Nuclear Science。

S. Aoki: "The Observation of the Muonic Decay D_S *munu" Prog. Theor. Phys.89. 131-138 (1993)

S. Aoki：“Muonic 衰变 D_S *munu 的观察”Prog。

K. Kodama: "The Study of Charm Production in Nucleus-Nucleus Central Interaction" International Symposium on High Energy Nuclear Collsions and Quark Gluon Plasma Kyoto, Japan June 6-8, 1991. 150-155 (1992)

K. Kodama：“核-核中心相互作用中魅力产生的研究”高能核碰撞和夸克胶子等离子体国际研讨会，日本京都，1991年6月6-8日。150-155（1992）