NUCLEAR MATTER AT FINITE TEMPERATURE AND DENSITY: THEORY AND EXPERIMENT

ROGER WAYNE MINICH, Purdue University

Abstract

The consequences of a phase transition associated with symmetry restoration to SU(2) x SU(2) in nuclear matter are investigated. The changes in the mass spectrum due to the phase transition (a) at zero temperature and high density, and (b) at high temperature with zero chemical potential are evaluated in the (sigma) model of particle physics. The experimentally observable effects necessitate the measurement of current correlation functions. In this thesis, the Vector-Vector-Axial vector (VVA) and the Vector-Vector-Pseudoscalar (VVP) current correlation functions are evaluated. The relation between the VVA and VVP correlation functions is obtained and it is shown that the Adler-Bell-Jackiw anomaly in the divergence of the axial vector current remains unaltered in the nuclear medium, even though the VVA and the VVP correlation functions have additional contributions from processes specific to the many-particle system. The VVP correlation function is related to the neutral-pion decay amplitude. The changes in the decay rate of (pi)(DEGREES) (--->) 2(gamma) in the nuclear medium are evaluated by including the effects of changes in the mass spectrum of particles, and by using the cutting rules of many-body field theory for the real and imaginary parts of the amplitude. The photon in the nuclear medium is dressed by polarization effects and propagates as a plasmon. This effect is taken into account by evaluating the plasmon frequency or the plasmon mass. The changes in the mass spectrum due to symmetry restoration affect the decay rate of (pi)(DEGREES) (--->) 2(gamma) by at least two orders of magnitude and these results are tabulated. The Primakoff effect ((gamma)+'(gamma)' (--->) (pi)(DEGREES)) is proposed as a means of providing the signal for the "abnormal phase." An expression for the Primakoff differential cross section is derived taking into account nuclear absorption effects, the nonuniform nuclear density, and a background contribution arising from strong coherent nuclear processes. Finally, the new field of relativistic nuclear fragmentation is introduced. A phenomenological analysis of recent FNAL data involving proton-nucleus collisions (E591) is carried out. The preliminary data is discussed in the context of various statistical models including fission and evaporation. A new statistical model, the droplet model, is suggested to explain some of the main features of nuclear fragmentation.

Degree

Ph.D.

Subject Area

Particle physics

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