Relativistic treatment of the interactions of electromagnetic probes with complex nuclei

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" Relativistic treatment of the interactions of electromagnetic probes with complex nuclei "
M. Hedayatipoor H. S. Sherif

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113094
Doc. No	:	TLpq304388295
Main Entry	:	H. S. Sherif
	:	M. Hedayatipoor
Title & Author	:	Relativistic treatment of the interactions of electromagnetic probes with complex nuclei\ M. HedayatipoorH. S. Sherif
College	:	University of Alberta (Canada)
Date	:	1997
student score	:	1997
Degree	:	Ph.D.
Page No	:	201
Abstract	:	The interactions of electromagnetic probes with nuclei are studied. In the first part of this thesis the relationship between relativistic and nonrelativistic approaches to nucleon knock-out reactions is investigated. The relativistic amplitudes for the proton knock-out reactions usd(\gamma,p)usd and usd(e,\ e\sp\prime p)usd on nuclei are reduced to the nonrelativistic forms using an effective Pauli reduction scheme. The reductions are carried out to second order in the inverse nucleon mass. It is found that the interaction Hamiltonians appearing in the nonrelativistic amplitude have significant dependence on the vector and scalar mean nuclear potentials. These strong medium modifications are absent in traditional nonrelativistic calculations. Detailed comparisons show that these modifications are crucial to understanding the differences between relativistic and nonrelativistic models. These differences are also examined through reduction of the relativistic Hamiltonian for the first reaction via the Foldy-Wouthuysen transformation. Similar medium modifications are obtained in this case as well. We discuss the implications of these medium modifications for the consistency of existing non-relativistic calculations. In the second part of this thesis, a relativistic model for photoproduction of usd\etausd mesons from complex nuclei is developed. The model is used to study the exclusive reaction Ausd(\gamma,\eta p)usdA-1, leading to discrete final states in the residual nucleus. Inclusive reactions Ausd(\gamma,\eta)usdX in which the usd\etausd meson is the only detected particle are also studied. The ingredients of the model are: (i) the nucleon wavefunctions are solutions of the Dirac wave equation with the appropriate scalar and vector strong potentials, (ii) the usd\etausd meson is described by solutions of the Klein-Gordon equation with appropriate optical potentials, and (iii) the interactions between the fields are introduced through a covariant effective Lagrangian. The amplitudes are used to calculate the observables for the exclusive and inclusive reactions on different target nuclei. The energy region where the S(1535) resonance dominates the reaction is specified. This is the best energy region for using the usd\etausd photoproduction reactions to study the properties of the above resonance in the nuclear medium. The region of phase space where the reaction has its largest cross section is also determined. Comparison with the existing nonrelativistic calculations is carried out. Detailed comparison of the inclusive reactions with the available data show that, in the energy regions studied, the quasifree usd\etausd production is the main contributing process to inclusive usd\etausd photoproduction reactions.
Subject	:	photoproduction
	:	Physics
	:	Pure sciences