Measuring Hanbury Brown-Twiss correlations of pions in high-energy nucleus-nucleus collisions

This dissertation examines how particle detectors extract information about correlations due to the Hanbury Brown-Twiss (HBT) effect for identical pions from the collision debris of a high-energy collision between two heavy nuclei. The basic ingredients of HBT correlations are: the exchange symmetry ( antisymmetry) of the wave function for identical bosons ( fermions) at the detectors, single-particle state noise, and wave coherence. We analyze how the wave packet nature of pions created in a high-energy collision affects the form of HBT correlations of like-pions, how gaseous ionization chambers used in high-energy physics to measure pion momenta detect the momentum correlations, and we determine the effect the length and time scales involved in detecting HBT have on measurements of the correlations. We also investigate the effect of pion emission delay times and the effect of an extended distribution of elementary pion radiators on HBT correlation measurements. The results of our investigation show that pairs of pion wave packets must arrive at each detector together, within a time window determined by the atomic ionization time, in order for the momentum correlations of like-pion pairs to be observed. We find that measurements of the HBT correlation for pions are not appreciably affected either by the time scales important for detecting pion correlations or delays in pion emission times much shorter than the ionization time scale of tracking detectors. Using a simple model of pion production, we show that the effective relative momentum scale of the pair correlation function depends on both the overall source size and lifetime and those of the elementary pion radiators. Finally, we have developed a simple framework (by way of examining the HBT effect for pions as detected by wire chamber detectors) from elementary quantum mechanics for computing measurements of correlations among particles produced in high-energy physics experiments.U of I Onlydissertation/thesi