Study of Hadron Production in High Energy Heavy Ion Reaction

欧洲核子研究中心158 A GeV/c Pb+Pb碰撞的数据收集工作已经完成，飞行时间探测器已按计划运往布鲁克海文国家实验室，用于安装PHENIX实验。在需要的地方对飞行时间探测器进行了调整、修理和修改。对PHENIX实验的数据读出进行了系统校验。今年的主要工作是数据分析。首先，从欧洲核子研究中心采集的数据证实，飞行时间探测器达到了设计的80皮秒的定时分辨率。在数据分析方面，我们在97年夏天邀请了来自日内瓦大学的两位合作者，这大大提高了协作之间的沟通和数据分析的速度。结果首次发现了能量为158 a GeV/c的PB+PB碰撞中的定向流动。对这种流体动力学效应的分析，特别是对光束能量依赖性的分析，被认为对表征夸克胶子等离子体形成的物质状态方程提供了重要的信息。第十三届超相对论核- nacleus碰撞国际会议于1997年12月1日至5日在筑波大学大学堂举行。在这一系列会议中，这是第一次在亚洲举行的会议。该研究组的八木耕介（Kohsuke Yagi）担任主席，初田哲夫（Tetsuo Hatsuda）和三宅康夫（Yasuo Miake）担任科学秘书。该小组发表了几篇报告，其中158 A GeV/c能量下的水动力效应是本次会议的重要议题之一。

Data collection in 158 A GeV/c Pb+Pb collisions at CERN has been completed and the time of flight detector has been shipped to Brookhaven National Laboratory for the installation to the PHENIX experiment as is planned. Tuning, repair and modifications to the time-of-flight detector has been done where needed. System chack of the data readout for the PHENIX experiment was also crarried out.Major activity of this years was the data analysis. First of all, it has been confirmed from the data taken at the CERN that the time-of-flight detector has achived the timing resolution of 80 pico second as is designed. For the data analysis, we invited two collaborators from Univ of Geneve during the summer of '97, which improved the communication among the collaboration significantly and the speed of the data analysis.As a result, directed flow in PB+PB collisions at the energy of 158 A GeV/c has been found as a first time at this energy. The analysis of the such hydrodynamical effect, particularly, the beam energy dependence of the effect, is believed to provide important information on the equation of state of the matter, which characterizes the formation of Quark Gluon Plasma.The Thirteenth International Conference on Ultra-Relativistic Nucleus-Nacleus Collisions was held on December 1-5,1997 at the university hall of the university of Tsukuba. In this series of conference this was the first conference held in Asia. Kohsuke Yagi of this research group served as a chairperson, and Tetsuo Hatsuda and Yasuo Miake as scientific secretaries of this conference. Several reports were made from this group and the hydrodynamical effect at the energy of 158 A GeV/c was one of the important topics at this conference.