A microscopic description of elastic scattering from unstable nuclei within a relativistic framework

Yahya, Wasiu Akanni (2018-03)

Thesis (PhD)--Stellenbosch University, 2018.

Thesis

ENGLISH SUMMARY: In this dissertation, a microscopic study of proton elastic scattering from unstable nuclei at intermediate energies using relativistic formalisms is presented. We have employed both the original relativistic impulse approximation (IA1) and the generalised relativistic impulse approximation (IA2) formalisms to calculate the relativistic optical potentials, with target densities derived from relativistic mean field (RMF) theory using the QHD-II, NL3, and FSUGold parameter sets. Comparisons between the optical potentials computed using both IA1 and IA2 formalisms, and the different RMF Lagrangians are presented for both stable and unstable targets. The comparisons are required to study the effect of using IA1 versus IA2 optical potentials, with different RMF parameter sets, on elastic scattering observables for unstable targets at intermediate energies. We also study the effect of full-folding versus factorized form of the optical potentials on elastic scattering observables. As with the case for stable nuclei, we found that the use of full-folding optical potential improves the scattering observables (especially spin observables) at low intermediate energy (e.g. 200MeV). No discernible difference is found at projectile incident energy of 500 MeV. To check the validity of using localized optical potential, we calculate the scattering observables using non-local potentials by solving the momentum space Dirac equation. The Dirac equation is transformed to two coupled Lippmann-Schwinger equations, which are then numerically solved to obtain the elastic scattering observables. The results are discussed and compared to calculations involving local coordinate-space optical potentials.

AFRIKAANSE OPSOMMING: In hierdie proefskrif word ’n mikroskopiese model vir elastiese proton verstrooiing van onstabiele kerne ondersoek deur gebruik te maak van ’n relatiwistiese formulering. Die NN interaksie word beskryf deur die sogenaamde IA1 en IA2 modelle. Die kernstruktuur word beskryf deur gebruik te maak van drie verskillende relatiwistiese gemiddelde-veld modelle, naamlik QHDII, NL3 en FSUGold. Die optiese kernpotensiaal word bereken met behulp van die IA1 en IA2 NN interaksies sowel as die drie verskillende kernstruktuur modelle, QHDII, NL3 en FSUGold. Sodoende kan ’n volledige stel verstrooiingswaarneembares bereken word vir elastiese verstrooiing van onstabiele kerne. Die kern optiesepotensiaal word ook op twee maniere bereken, naamlik die optimale faktoriseringsmetode en die volle oorvleuelingsmodel. Vir lae energie van die orde van 200 MeV, gee volle oorvleuelingsmodel ’n verbetering in die resultate van die spinwaarneembares. By ’n projektielenergie van ongeveer 500 MeV is daar egter geen beduidende verskil tussen hierdie twee metodes nie. Die Dirac vergelyking in momentum-ruimte word ook opgelos om ’n nie-lokale optiese kernpotensiaal te bereken. Die Dirac vergelyking word herskryf in terme van twee gekoppelde Lippmann-Schwinger vergelykings wat dan opgelos word om die elastiese spinwaarneembares te bepaal. Die resultate van hierdie berekening word dan bespreek en word vergelyk met berekeninge wat gedoen word vir lokale kern optiesepotensiale in posisie-ruimte.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103588
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