Hadron Single- and Multiparticle Measurements to Search for Phase Transitions in Ultrarelativistic Pb+Pb Collisions

Mikhail Leonidovich Kopytine

$\begin{approval} \member{Prof. Barbara Jacak (Thesis Advisor) \\ SUNY at Stony ... ...yak \\ SUNY at Stony Brook} \member{Dr. Dmitri Kharzeev \\ BNL} \end{approval}$

Abstract:

Hadron production in the 158 A GeV/c Pb

Pb collisions at the CERN SPS is studied in the NA44 Experiment. Yields and differential distributions of

, $\pi^+$ , $\pi^-$ in transverse kinetic energy and rapidity are measured around the center-of-mass rapidity. A considerable enhancement of

production per $\pi$ is observed, as compared to

collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.

A Si pad array covering pseudorapidity $1.5 < \eta < 3.3$ is used for an event-by-event study of the interactions. We apply a multiresolution analysis, based on a Discrete Wavelet Transformation, to probe the texture of particle distributions event-by-event, allowing simultaneous localization of features in space and scale. Scanning a broad range of multiplicities, we search for signals of clustering and of critical behaviour in the power spectra of local density fluctuations. The data are compared with detailed simulations of detector response, using heavy ion event generators, and with a reference sample created via event mixing. An upper limit is set on the probability and magnitude of dynamical fluctuations.

Contents

Mikhail Kopytine 2001-08-09