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Physics / M. Sc. (Physics)

A two-dimensional integrodi erential equation resulting from the use of potential harmonics expansion in the many-body Schr odinger equation is used to study ground-state properties of selected few-body nuclear systems. The equation takes into account twobody correlations in the system and is applicable to few- and many-body systems. The formulation of the equation involves the use of the Jacobi coordinates to de ne relevant global coordinates as well as the elimination of center-of-mass dependence. The form of the equation does not depend on the size of the system. Therefore, only the interaction potential is required as input. Di erent nucleon-nucleon potentials and hyperon-nucleon potentials are employed to construct the Hamiltonian of the systems. The results obtained are in good agreement with those obtained using other methods. / Physics

Physics / M. Sc. (Physics)

A two-dimensional integrodi erential equation resulting from the use of potential harmonics expansion in the many-body Schr odinger equation is used to study ground-state properties of selected few-body nuclear systems. The equation takes into account twobody correlations in the system and is applicable to few- and many-body systems. The formulation of the equation involves the use of the Jacobi coordinates to de ne relevant global coordinates as well as the elimination of center-of-mass dependence. The form of the equation does not depend on the size of the system. Therefore, only the interaction potential is required as input. Di erent nucleon-nucleon potentials and hyperon-nucleon potentials are employed to construct the Hamiltonian of the systems. The results obtained are in good agreement with those obtained using other methods. / Physics / M.Sc. (Physics)

Electromagnetic processes induced by electron scattering off few-nucleon systems are theoretically investigated in the non-relativistic formalism. Non-relativistic one-body nuclear current operators are used with a parametrization of nucleon electromagnetic form factors based on recent experimental nucleon scattering data. Electromagnetic form factors of three-nucleon and four-nucleon systems are calculated from elastic electron-nucleus scattering information. Nuclear response functions used in the determination of differential cross sections for inclusive and exclusive quasi-elastic electron-nucleon scattering from the 4He nucleus are also calculated. Final-state interactions in the quasi-elastic nucleon knockout process are explicitly taken into account using the Glauber approximation. The sensitivity of the response functions to the final-state interactions is investigated. The Antisymmetrized Molecular Dynamics approach with angular momentum and parity projection is employed to construct ground state wave functions for the nuclei. A reduced form of the realistic Argonne V18 nucleon-nucleon potential is used to describe nuclear Hamiltonian. A convenient numerical technique of approximating expectation values of nuclear Hamiltonian operators is employed. The constructed wave functions are used to calculate ground-state energies, root-mean-square radii and magnetic dipole moments of selected light nuclei. The theoretical predictions of the nuclear properties for the selected nuclei give a satisfactory description of experimental values. The Glauber approximation is combined with the Antisymmetrized Molecular Dynamics to generate wave functions for scattering states in quasi-elastic scattering processes. The wave functions are then used to study proton knockout reactions in the 4He nucleus. The theoretical predictions of the model reproduce experimental observation quite well. / Physics / Ph D. (Physics)

Electromagnetic processes induced by electron scattering off few-nucleon systems are theoretically investigated in the non-relativistic formalism. Non-relativistic one-body nuclear current operators are used with a parametrization of nucleon electromagnetic form factors based on recent experimental nucleon scattering data. Electromagnetic form factors of three-nucleon and four-nucleon systems are calculated from elastic electron-nucleus scattering information. Nuclear response functions used in the determination of differential cross sections for inclusive and exclusive quasi-elastic electron-nucleon scattering from the 4He nucleus are also calculated. Final-state interactions in the quasi-elastic nucleon knockout process are explicitly taken into account using the Glauber approximation. The sensitivity of the response functions to the final-state interactions is investigated. The Antisymmetrized Molecular Dynamics approach with angular momentum and parity projection is employed to construct ground state wave functions for the nuclei. A reduced form of the realistic Argonne V18 nucleon-nucleon potential is used to describe nuclear Hamiltonian. A convenient numerical technique of approximating expectation values of nuclear Hamiltonian operators is employed. The constructed wave functions are used to calculate ground-state energies, root-mean-square radii and magnetic dipole moments of selected light nuclei. The theoretical predictions of the nuclear properties for the selected nuclei give a satisfactory description of experimental values. The Glauber approximation is combined with the Antisymmetrized Molecular Dynamics to generate wave functions for scattering states in quasi-elastic scattering processes. The wave functions are then used to study proton knockout reactions in the 4He nucleus. The theoretical predictions of the model reproduce experimental observation quite well. / Physics / Ph D. (Physics)

Nuclear electromagnetic breakup processes at low energy are particularly relevant in the astrophysical context. In this Thesis we analyse the Beryllium-9 photodisintegration reaction, whose inverse process, under certain astrophysical conditions, is related to the Carbon-12 formation. A preliminary study of the Carbon-12 photodisintegration is also carried out. The interaction of these nuclei with a low-energy photon induces a transition to a state consisting of cluster sub-units, the alpha-particles, and possibly a neutron, n. The theoretical study of the cross section in the low-energy regime is conducted by using a three-body ab initio approach. Beryllium-9 exhibits a clear separation of energy scales, since its alpha-alpha-n three-body binding energy is shallow compared to the binding of the alpha-particle. Within this framework a halo/cluster Effective Field Theory (EFT) can be developed. The alpha-alpha and alpha-n effective interactions are defined in momentum space as a series of contact terms, regularized by a momentum-regulator function. The Low Energy Constants are expressed in terms of scattering observables, i.e. scattering length and effective range. A three-body potential is also introduced in the model. Carbon-12 is studied on the same footing. By means of an integral transform approach, the problem of the transition to a state in the continuum can be advantageously reformulated in terms of a bound-state problem: in the calculations we use the Lorentz Integral Transform method, in conjunction with the Non-Symmetrized Hyperspherical Harmonics method. In determining the low-energy photodisintegration cross section, the nuclear current matrix element is evaluated through the electric dipole, or quadrupole, transition operator (Siegert theorem). Since the continuity equation is used explicitly, the contribution of the one-body and the many-body current operators is implicitly included in the calculation. By comparing the results with those obtained by using a one-body convection current, the effect of the many-body terms can be quantified. The dependence of the results on different EFT parameters is discussed, always in connection with the experimental data available in the literature. By following the power counting dictated by the EFT approach for Beryllium-9, the inclusion of different partial waves in the potential model is explored. In addition to a alpha-alpha S-wave, a alpha-n P-wave and a three-body effective interaction, a alpha-n S-wave term is also required to obtain results more consistent with the experimental data. The contribution of the many-body currents to the cross section is found to be non-negligible. Although at an early stage, Carbon-12 results show interesting features. The formalism presented in this Thesis can be extended to study the photodisintegration of Oxygen-16 within a fully four-body ab initio approach.