Experimental Study on Quark-Gluon-Plasma at BNL

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The experiment with high-intensity 14.5 AGeV Si-beams and the first-round experiment with 11 AGeV Au-beams have been carried out by the Japan-US international collaboration in high energy heavy ion collisions at the AGS, Brookhaven National Laboratory, USA.Primary goals of the experiment are (1) to study the two-particle correlations for pions and Kaons, and (2) to measure the rarely-produced hadrons (i.e. K-and anti-proton) with good statistics using the experimental system with a magnetic spectrometer as a central device.Space-time evolution of nucleus-nucleus collisions could be investigated through two-particle correlation measurement. Trial of measuring K-and anti-proton were made before, but low statistics prevented us to deduce any conclusions for their productions.In order to achieve the goals, we built a special trigger system by which particle identification in the trigger-level was made possible. Stringent event selection capability made it possible to run with high-intensity beams.Data analyses of two particle correlations are in progress, and preliminary result shows that source size measuremed by pions is significantly smaller than that measured by Kaons.Anti-proton yield was consisten with the model calculation with no anti-protons absorption in nuclear matter, which strongly contradicts to the naive expectation.With the completion of AGS-Booster, experiments with heavy ions up to Au became possible. We can expect a better condition to study unclear matter at extreme conditions with heavy ions. The first Au beam was available in May, 1992, and we had a prelminary short run. Purity of Au beam was better than 99%. Measurements of transverse and forward energy flow were made. Measurement of particle spectra at backward angle with spectrometer were also tried.Data analysis going on, and the construction of a new spectrometer which covers the forward angular region is in progress.