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Systematic measurement of hadron production for the study of Quark-Gluon Plasma

用于夸克-胶子等离子体研究的强子产生的系统测量

基本信息

批准号：
06102004
负责人：
MIAKE Yasuo
金额：
$ 144万
依托单位：
Insutitute of Physics,Unibersity of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06102004/
关键词：
Big Bang Quark Gluon Plasma Relativistic Heavy Ion Collisions Time of Flight Counter Directed Flow Elliptic Flow Directed Flow Elliptic Flow クォークグルオンプラズマ流体力学的振舞ビックバン超高温,高密度ハドロン生成飛行時間測定クオーク・グルオンブラズマ相対論的高エネルギー重イオン衝突ピツ

项目摘要

During the period of the birth of the Universe, it is speculated that the universe was in an unknown from of matter, called quark-gluon plasma (QGP). Unique opportunity to re-create the QGP in the laboratory is provided by high energy heavy ion collisions. Systematic study of hadron production in the collisions is essentially important for the basic understanding of the complex system, which might characterize the formation of the QGP.High resolution time-of flight (TOF) counters (resolution in sigma ; <85 ps), which provides the key role for the particle identification of the hadron, has been constructed. Pipeline readout circuits for high resolution TOF measurement have been developed together with Nevis Lab., Columbia University. Utilizing the TOF system, systematic measurement of the produced hadrons has been carried out in heavy ion collisions at the energy of <10 A GeV, 158A GeV and 100+100 AGeV as planned.Among several achievements, study of collective emissions of particles in PB+PB collisions at the energy of 158 A GeV/c is important. From an event-by-event analysis of the azimuthal correlation of protons emitted at the target rapidity region, directed flow has been observed as a first time at this energy of heavy ion collisions. The magnitude of the directed flow is found to be smaller than those observed at 10A GeV and also smaller than those predicted by RQMD model. This fact may suggest a softening of equation of state, which characterizes the formation of Quark Gluon Plasma. With respect to the reaction plane, determined from the measurement of the directed flow, azimuthal correlation of K+, pion and proton near mid-rapidity have been observed. In semi-central collisions, K+ mesons are found to be preferentially emitted out of the reaction plane while pions and protons are emitted in the reaction plane. The result suggest that the K+ emission is influenced by in-medium potential effects in addition to the collective flow effects.

在宇宙诞生期间，人们推测宇宙处于一种未知的物质状态，称为夸克胶子等离子体（QGP）。高能重离子碰撞提供了在实验室中重新创建 QGP 的独特机会。对碰撞中强子产生的系统研究对于对复杂系统的基本理解至关重要，这可能表征 QGP 的形成。高分辨率飞行时间 (TOF) 计数器（分辨率为 sigma；<85 ps）已经建成，它为强子的粒子识别提供了关键作用。用于高分辨率 TOF 测量的管道读出电路是与哥伦比亚大学 Nevis 实验室共同开发的。利用TOF系统，按计划对<10 A GeV、158A GeV和100+100 AGeV能量的重离子碰撞中产生的强子进行了系统测量。其中，对158 A GeV/c能量的PB+PB碰撞中粒子集体发射的研究是重要的。通过对目标快速区域发射的质子的方位相关性的逐事件分析，首次在重离子碰撞的这种能量下观察到定向流。发现定向流的大小小于 10A GeV 下观察到的大小，也小于 RQMD 模型预测的大小。这一事实可能表明状态方程的软化，这是夸克胶子等离子体形成的特征。对于反应平面，根据定向流的测量确定，观察到 K+、π介子和质子接近中速的方位角相关性。在半中心碰撞中，发现 K+ 介子优先发射出反应平面，而π介子和质子则在反应平面内发射。结果表明，除了集体流动效应之外，K+发射还受到介质内电势效应的影响。