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Michigan State University

1. Titus, Luke. Effects of nonlocality on transfer reactions.

Degree: 2016, Michigan State University

URL: http://etd.lib.msu.edu/islandora/object/etd:3929

Thesis Ph. D. Michigan State University. Physics 2016.

Nuclear reactions play a key role in the study of nuclei away from stability. Single-nucleon transfer reactions involving deuterons provide an exceptional tool to study the single-particle structure of nuclei. Theoretically, these reactions are attractive as they can be cast into a three-body problem composed of a neutron, proton, and the target nucleus.Optical potentials are a common ingredient in reactions studies. Traditionally, nucleon-nucleus optical potentials are made local for convenience. The effects of nonlocal potentials have historically been included approximately by applying a correction factor to the solution of the corresponding equation for the local equivalent interaction. This is usually referred to as the Perey correction factor. In this thesis, we have systematically investigated the effects of nonlocality on (p,d) and (d,p) transfer reactions, and the validity of the Perey correction factor. We implemented a method to solve the single channel nonlocal equation for both bound and scattering states. We also developed an improved formalism for nonlocal interactions that includes deuteron breakup in transfer reactions. This new formalism, the nonlocal adiabatic distorted wave approximation, was used to study the effects of including nonlocality consistently in (d,p) transfer reactions. For the (p,d) transfer reactions, we solved the nonlocal scattering and bound state equations using the Perey-Buck type interaction, and compared to local equivalent calculations. Using the distorted wave Born approximation we construct the T-matrix for (p,d) transfer on ^{17}O, ^{41}Ca, ^{49}Ca, ^{127}Sn, ^{133}Sn, and ^{209}Pb at 20 and 50 MeV. Additionally we studied (p,d) reactions on ^{40}Ca using the the nonlocal dispersive optical model. We have also included nonlocality consistently into the adiabatic distorted wave approximation and have investigated the effects of nonlocality on on (d,p) transfer reactions for deuterons impinged on ^{16}O, ^{40}Ca, ^{48}Ca, ^{126}Sn, ^{132}Sn, ^{208}Pb at 10, 20, and 50 MeV. We found that for bound states the Perry corrected wave functions resulting from the local equation agreed well with that from the nonlocal equation in the interior region, but discrepancies were found in the surface and peripheral regions. Overall, the Perey correction factor was adequate for scattering states, with the exception for a few partial waves. Nonlocality in the proton scattering state reduced the amplitude of the wave function in the nuclear interior. The same was seen for nonlocality in the deuteron scattering state, but the wave function was also shifted outward. In distorted wave Born approximation studies of (p,d) reactions using the Perey-Buck potential, we found that transfer distributions at the first peak differed by 15-35% as compared to the distribution resulting from local potentials. When using the dispersive optical model, this discrepancies grew to \approx 30-50%.…

Subjects/Keywords: Particles (Nuclear physics); Nuclear optical potentials; Nuclear reactions; Physics; Nuclear physics and radiation; Quantum physics

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APA (6^{th} Edition):

Titus, L. (2016). Effects of nonlocality on transfer reactions. (Thesis). Michigan State University. Retrieved from http://etd.lib.msu.edu/islandora/object/etd:3929

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Titus, Luke. “Effects of nonlocality on transfer reactions.” 2016. Thesis, Michigan State University. Accessed September 26, 2020. http://etd.lib.msu.edu/islandora/object/etd:3929.

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Titus, Luke. “Effects of nonlocality on transfer reactions.” 2016. Web. 26 Sep 2020.

Vancouver:

Titus L. Effects of nonlocality on transfer reactions. [Internet] [Thesis]. Michigan State University; 2016. [cited 2020 Sep 26]. Available from: http://etd.lib.msu.edu/islandora/object/etd:3929.

Note: this citation may be lacking information needed for this citation format:

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Titus L. Effects of nonlocality on transfer reactions. [Thesis]. Michigan State University; 2016. Available from: http://etd.lib.msu.edu/islandora/object/etd:3929

Not specified: Masters Thesis or Doctoral Dissertation

Michigan State University

2. Quinn, Stephen J. Capture cross sections for the astrophysical p process.

Degree: 2015, Michigan State University

URL: http://etd.lib.msu.edu/islandora/object/etd:2354

Thesis Ph. D. Michigan State University. Physics 2015

This dissertation includes the design and development of the Summing NaI (SuN) 4pi gamma-ray detector at the National Superconducting Cyclotron Laboratory to measure proton and alpha radiative capture reactions relevant in the astrophysical p process. Discussions of p-process nucleosynthesis, the relevant nuclear reaction theory, experimental details, and analysis procedures are included. All reaction measurements were performed at the Nuclear Science Laboratory of the University of Notre Dame. The commissioning experiments in both regular and inverse kinematics were done using known resonances in the 27Al(p,g)28Si and 58Ni(p,g)59Cu reactions, and the results agree well with previous literature values. The success of these proof-of-principle measurements marks the first time that the gamma-summing technique has been implemented in inverse kinematics. Furthermore, in an effort to investigate the synthesis of the light p-process nuclei, the 74Ge(p,g)75As, 74Ge(a,g)78Se, and 90,92Zr(a,g)94,96Mo reactions were measured and compared to theoretical calculations using the nuclear statistical model. It was found that the new 74Ge(p,g)75As measurements cause an enhancement in the overproduction of 74Se in p-process models, and that the updated 90Zr(a,g)94Mo reaction rate seems to confirms the p-process branching point at 94Mo. Finally, the 58Ni(a,g)62Zn reaction was measured for its role in nucleosynthesis in type Ia supernovae. The measurements here lower the reaction rate used in astrophysical models, which leads to a 5% reduction in the calculated abundances of several isotopes. All of the measurements in this dissertation greatly reduce the uncertainty in the reaction cross section.

Description based on online resource;

Subjects/Keywords: Stable isotopes – Research; Nucleosynthesis – Research; Nuclear physics; Physics; Astrophysics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Quinn, S. J. (2015). Capture cross sections for the astrophysical p process. (Thesis). Michigan State University. Retrieved from http://etd.lib.msu.edu/islandora/object/etd:2354

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Quinn, Stephen J. “Capture cross sections for the astrophysical p process.” 2015. Thesis, Michigan State University. Accessed September 26, 2020. http://etd.lib.msu.edu/islandora/object/etd:2354.

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Quinn, Stephen J. “Capture cross sections for the astrophysical p process.” 2015. Web. 26 Sep 2020.

Vancouver:

Quinn SJ. Capture cross sections for the astrophysical p process. [Internet] [Thesis]. Michigan State University; 2015. [cited 2020 Sep 26]. Available from: http://etd.lib.msu.edu/islandora/object/etd:2354.

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Quinn SJ. Capture cross sections for the astrophysical p process. [Thesis]. Michigan State University; 2015. Available from: http://etd.lib.msu.edu/islandora/object/etd:2354

Not specified: Masters Thesis or Doctoral Dissertation

Michigan State University

3. Morris, Titus Dan. Systematic improvements of ab-initio in-medium similarity renormalization group calculations.

Degree: 2016, Michigan State University

URL: http://etd.lib.msu.edu/islandora/object/etd:3864

Thesis Ph. D. Michigan State University. Physics 2016

The In-Medium Similarity Renormalization Group (IM-SRG) is an ab initio many-body method that has enjoyed increasing prominence in nuclear theory, due to its soft polynomial scaling with system size, and the flexibility to target ground and excited states of both closed- and open-shell systems. Despite many successful applications of the IM-SRG to microscopic calculations of medium-mass nuclei in recent years, the conventional formulation of the method suffers a number of limitations. Key amongst these are i) large memory demands that limit calculations in heavier systems and render the calculation of observables besides energy spectra extremely difficult, and ii) the lack of a computationally feasible sequence of improved approximations that converge to the exact solution in the appropriate limit, thereby verifying that the IM-SRG is systematically improvable. In this thesis, I present a novel formulation of the IM-SRG based on the Magnus expansion. I will show that this improved formulation, guided by intuition gleaned from a diagrammatic analysis of the perturbative content of different truncations and parallels with coupled-cluster theory, allows one to bypass the computational limitations of traditional implementations, and provides computationally viable approximations that go beyond the truncations used to date. The effectiveness of the new Magnus formulation is illustrated for several many-nucleon and many-electron systems.

Description based on online resource;

Subjects/Keywords: Nuclear physics – Mathematical models; Mass (Physics) – Measurement; Physics; Nuclear physics and radiation

Record Details Similar Records

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Morris, T. D. (2016). Systematic improvements of ab-initio in-medium similarity renormalization group calculations. (Thesis). Michigan State University. Retrieved from http://etd.lib.msu.edu/islandora/object/etd:3864

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Morris, Titus Dan. “Systematic improvements of ab-initio in-medium similarity renormalization group calculations.” 2016. Thesis, Michigan State University. Accessed September 26, 2020. http://etd.lib.msu.edu/islandora/object/etd:3864.

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Morris, Titus Dan. “Systematic improvements of ab-initio in-medium similarity renormalization group calculations.” 2016. Web. 26 Sep 2020.

Vancouver:

Morris TD. Systematic improvements of ab-initio in-medium similarity renormalization group calculations. [Internet] [Thesis]. Michigan State University; 2016. [cited 2020 Sep 26]. Available from: http://etd.lib.msu.edu/islandora/object/etd:3864.

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Morris TD. Systematic improvements of ab-initio in-medium similarity renormalization group calculations. [Thesis]. Michigan State University; 2016. Available from: http://etd.lib.msu.edu/islandora/object/etd:3864

Not specified: Masters Thesis or Doctoral Dissertation