EXPERIMENTAL EVIDENCE FOR CRITICAL PHENOMENA IN HADRONIC MATTER FROM NUCLEAR FRAGMENTATION INDUCED BY HIGH ENERGY PROTONS

JAMES EDWARD FINN, Purdue University

Abstract

This thesis contains the significant results of an experiment designed to search for new nuclear states which might be produced in the interaction of nuclei with high energy protons. This experiment in which the nuclear fragment's charge, mass and kinetic energy were determined is described. Inclusive fragment isotopic yields and kinetic energy spectra are obtained through data analysis for fragment charge 3 (LESSTHEQ) Z(,f) (LESSTHEQ) 13 from Xenon and Krypton targets. The relative fragment mass yields are observed to follow a power law as a function of mass number with power (TURN)2.65. The significance of this observation is explored through a study of phase transitions and critical phenomena. The fragmentation process is treated as condensation near the critical point. In analogy to a hot Van der Waals gas, fragmentation is envisaged as the formation of droplets of nucleons in an excited nuclear system near the critical point of nuclear matter. Fragments are interpreted as these droplets in a multibody nuclear disintegration. A critical temperature of 3.28 MeV is extracted. The fragment kinetic energy distributions are fit with a functional form which follows from the supposition that the fragments are formed inside an excited system. The characteristic 15 Mev slope of the K.E. spectra is interpreted as representative of the Fermi momentum. With the excitation temperature incorporated into the distribution the most probable Coulomb repulsion energies are obtained. Within a simple model these energies are translated into the most probable fragment locations inside the remnant which indicate that heavy fragments are formed predominantly near the remnant center. It is concluded that the data obtained in this experiment can be consistently described by a model which views the fragmentation process as a gas-liquid phase transition near the critical point. The observed nuclear fragments result from the transition from an abnormal gas-like nuclear state to the ordinary liquid-like nuclear state.

Degree

Ph.D.

Subject Area

Nuclear physics

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