Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at (square root)s{sub NN} = 130 GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freezeout. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.

This thesis contains the setup, analysis and results of experiment E684H Multi-Pion Correlations in Relativistic Heavy Ion Collisions''. The goals of the original proposal were: (1) To initiate the use of the HISS facility in the study of central Relativistic Heavy Ion Collisions (RHIC). (2) To perform a second generation experiment for the detailed study of the pion source in RHIC. The first generation experiments, implied by the second goal above, refer to pion correlation studies which the Riverside group had performed at the LBL streamer chamber. The major advantage offered by moving the pion correlation studies to HISS is that, being an electronic detector system, as opposed to the Streamer Chamber which is a visual detector, one can greatly increase the statistics for a study of this sort. An additional advantage is that once one has written the necessary detector and physics analysis code to do a particular type of study, the study may be extended to investigate the systematics, with much less effort and in a relatively short time. This paper discusses the Physics motivation for this experiment, the experimental setup and detectors used, the pion correlation analysis, the results, and the conclusions possible future directions for pion studies at HISS. If one is not interested in all the details of the experiment, I believe that by reading the sections on intensity interferometry, the section the fitting of the correlation function and the systematic corrections applied, and the results section, one will get a fairly complete synopsis of the experiment.

This book attempts to cover the fascinating field of physics of relativistic heavy ions, mainly from the experimentalist's point of view. After the introductory chapter on quantum chromodynamics, basic properties of atomic nuclei, sources of relativistic nuclei, and typical detector set-ups are described in three subsequent chapters. Experimental facts on collisions of relativistic heavy ions are systematically presented in 15 consecutive chapters, starting from the simplest features like cross sections, multiplicities, and spectra of secondary particles and going to more involved characteristics like correlations, various relatively rare processes, and newly discovered features: collective flow, high pT suppression and jet quenching. Some entirely new topics are included, such as the difference between neutron and proton radii in nuclei, heavy hypernuclei, and electromagnetic effects on secondary particle spectra.Phenomenological approaches and related simple models are discussed in parallel with the presentation of experimental data. Near the end of the book, recent ideas about the new state of matter created in collisions of ultrarelativistic nuclei are discussed. In the final chapter, some predictions are given for nuclear collisions in the Large Hadron Collider (LHC), now in construction at the site of the European Organization for Nuclear Research (CERN), Geneva. Finally, the appendix gives us basic notions of relativistic kinematics, and lists the main international conferences related to this field. A concise reference book on physics of relativistic heavy ions, it shows the present status of this field.

An application of intensity interferometry to relativistic heavy ion collisions is reported. Specifically, the correlation between two like-charged pions is used to study the reactions Ar+KCl.-->.2.pi./sup +-/+X and Ne+NaF.-->.2.pi.−+X. Source sizes are obtained that are consistent with a simple geometric interpretation. Lifetimes are less well determined but are indicative of a faster pion production process than predicted by Monte Carlo cascade calculations. There appears to be a substantial coherent component of the pion source, although measurement is complicated by the presence of final state interactions. Additionally, the generation of spectra of uncorrelated events is discussed. In particular, the influence of the correlation function on the background spectrum is analyzed, and a prescription for removal of this influence is given. A formulation to describe the statistical errors in the background is also presented. Finally, drawing from the available literature, a self-contained introduction to Bose-Einstein correlations and the Hanbury-Brown - Twiss effect is provided, with an emphasis on points of contact between classical and quantum mechanical descriptions.