Using light emitted clusters as a probe of the symmetry energy in the nuclear equation of state
The symmetry energy, and more specifically its density dependence, has been studied for quite some time from both a theoretical and experimental approach. In order to sufficiently constrain the symmetry energy, we need to experimentally measure observables sensitive to the symmetry energy within a reasonable uncertainty and compare those results to those of simulations of the same nuclear reactions. This dissertation aims to achieve both experimental measurements and compare them to the results of studies using the pBUU transport code.These studies using pBUU aimsto find the sensitivity of different observables to different transport variables as well as the symmetry energy itself. Some of the predominant variables that have been investigated in this dissertation are in-medium cross section between nucleons as well as the effect of cluster production. The specific observables upon which we report are the center of mass spectra of protons, neutrons, deuterons, tritons and finally \nuc{3}{He}. In addition we investigate the n/p and t/\nuc{3}{He} single and double ratios which have been suggested as being sensitive to the symmetry energy. As an added check we also study the coalescence invariant n/p spectra and ratios.We also include a study of spectra for all charged particles up through mass A=4 emitted from reactions of \nuc{112}{Sn}+\nuc{112}{Sn} and \nuc{124}{Sn}+\nuc{124}{Sn} at both 50 and 120 \meva. The experiment to measure these reactions used the Large Area Silicon Strip Array to detect the charged particles and the MSU Miniball to detect charge particle multiplicity in order to select central collisions. Neutrons were also measured in this experiment using the Large Area Neutron Array along with two thin scintillators used as a start timer for the neutron walls and a charge particle veto to discern contamination in the neutron walls. The neutron analyses are not extensively reported in this dissertation as they were the focus of the dissertation of Daniel Coupland. Finally, another scintillator was used to measure the beam rate.We compare the new experimental data with previous data. We have achieved higher statistical precision and measured up to higher emission energies. The 50 \meva data shows reasonable agreement with previous measurements. There are no prior measurements of the 120 \meva Sn+Sn reactions. Simulated results suggest a sensitivity to the density dependence of the symmetry energy, nevertheless there are still significant differences between the experimental data and simulated results. We present evidence that this is partly due to clustering effects in both the experiment and simulations. More theoretical work will need to be completed in order for the theory to be more accurately compared to the experimental results.
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- In Collections
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Electronic Theses & Dissertations
- Copyright Status
- In Copyright
- Material Type
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Theses
- Authors
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Youngs, Michael David
- Thesis Advisors
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Lynch, William G.
- Committee Members
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Mantica, Paul
Pratt, Scott
Tessmer, Stuart
Huston, Joey
- Date
- 2013
- Subjects
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Nuclear physics
Symmetry (Physics)
- Program of Study
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Physics - Doctor of Philosophy
- Degree Level
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Doctoral
- Language
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English
- Pages
- xii, 257 pages
- ISBN
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9781303206504
1303206501
- Permalink
- https://doi.org/doi:10.25335/b6ry-pk46