Study of Hadron Production in High Energy Heavy Ion Reaction

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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.