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Title: Quantum Tunneling and Scattering of a Composite Object.
Creator: Ahsan, Naureen, Volya, Alexander, Aldrovandi, Ettore, Piekarewicz, Jorge, Crede, Volker, Xiong, Peng, Department of Physics, Florida State University
Abstract/Description: Reaction physics involving composite objects with internal degrees of freedom is an important subject since it is encountered in the context of nuclear processes like fusion, fission, particle decay, as well as many other branches of science. Quantum tunneling and scattering of a composite object are explored in this work. A few model Hamiltonians are chosen as examples where a two-particle system interacts, in one dimension, with a target that poses a delta-potential or an infinite wall...
Show moreReaction physics involving composite objects with internal degrees of freedom is an important subject since it is encountered in the context of nuclear processes like fusion, fission, particle decay, as well as many other branches of science. Quantum tunneling and scattering of a composite object are explored in this work. A few model Hamiltonians are chosen as examples where a two-particle system interacts, in one dimension, with a target that poses a delta-potential or an infinite wall potential. It is assumed that only one of the two components interacts with the target. The study includes the harmonic oscillator and the infinite square well as examples of intrinsic Hamiltonians that do not allow the projectile to break up, and a finite square well and a delta-well as examples of Hamiltonians that do. The Projection Method and the Variable Phase Method are applied with the aim of an exact solution to the relevant scattering problems. These methods are discussed in the context of the pertinent convergence issues related thereto, and of their applicability. Virtual excitations of the projectile into the classically forbidden energy-domain are found to play a dominant and non-perturbative role in shaping reaction observables, giving rise to enhanced or reduced tunneling in various situations. Cusps and discontinuities are found to appear in observables as manifestations of unitarity and redistribution of flux at the thresholds. The intrinsic structure gives rise to resonance-like behavior in tunneling probabilities. It is also shown that there is charge asymmetry in the scattering of a composite object, unlike in the case of a structureless particle.
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Date Issued: 2011
Identifier: FSU_migr_etd-0142
Format: Thesis

Title: J/Psi -> E+E- Measurements in Cu + Cu Collisions at 200 Gev.
Creator: Das, Kushal, Crede, Volker, Safron, Sanford, Frawley, Anthony D., Capstick, Simon, Baer, Howie, Department of Physics, Florida State University
Abstract/Description: High-energy heavy-ion collisions are a powerful tool in the laboratory to investigate the phase transition from ordinary nuclear matter to a deconfined state of quarks and gluons, called the Quark-Gluon Plasma (QGP), which is predicted to be formed above a temperature of order Tc ~ 170 MeV in lattice Quantum Chromodynamics (QCD). Suppression of J/Ï production has long been considered to be one of the most promising signatures for the deconfinement of matter. J/Ï production has been measured...
Show moreHigh-energy heavy-ion collisions are a powerful tool in the laboratory to investigate the phase transition from ordinary nuclear matter to a deconfined state of quarks and gluons, called the Quark-Gluon Plasma (QGP), which is predicted to be formed above a temperature of order Tc ~ 170 MeV in lattice Quantum Chromodynamics (QCD). Suppression of J/Ï production has long been considered to be one of the most promising signatures for the deconfinement of matter. J/Ï production has been measured by the PHENIX experiment, one of the two major experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) in p + p, d + Au, Au + Au and Cu + Cu collisions at the center of mass energy per nucleon (âsNN) of 200 GeV. The analysis of the Cu + Cu data is the focus of this dissertation. Yields of J/Psi production in Cu + Cu collisions at âsNN = 200 GeV have been measured by the PHENIX experiment over the rapidity range |y|
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Date Issued: 2008
Identifier: FSU_migr_etd-0835
Format: Thesis

Title: Magneto-Raman Spectroscopy of Graphene and Graphite: Probing Electronic Structure and Electron-Phonon Interaction.
Creator: Kim, Younghee, Smirnov, Dmitry, Brooks, James, Stiegman, Albert E., Schlottmann, Pedro, Crede, Volker, Department of Physics, Florida State University
Abstract/Description: Single layer graphene (SLG) is a novel 2D system consisting of a single sheet of carbon atoms arranged in a honeycomb lattice, and exhibits a unique, linear low-energy dispersion. Bilayer graphene (BLG), two sheets stacked together, is an equally interesting system displaying a second unique, but hyperbolic, dispersion. Graphite consists of Bernal stacked graphene layers. Graphite band structure at K-point mimics the band structure of BLG, while at H- point it is similar to SLG. Hence,...
Show moreSingle layer graphene (SLG) is a novel 2D system consisting of a single sheet of carbon atoms arranged in a honeycomb lattice, and exhibits a unique, linear low-energy dispersion. Bilayer graphene (BLG), two sheets stacked together, is an equally interesting system displaying a second unique, but hyperbolic, dispersion. Graphite consists of Bernal stacked graphene layers. Graphite band structure at K-point mimics the band structure of BLG, while at H- point it is similar to SLG. Hence, depending on their momentum along the c axis, K-point electrons in bulk graphite behave as massive Dirac fermions in BLG. The carriers at the H-point have a character of massless particles due to the eectively vanishing inter-layer coupling. In this work, we study the inter-Landau level transitions of graphene and grpahite to probe the electron structure and electron-phonon interactions by using magneto-Raman spectroscopy. Raman spectroscopy is used extensively to characterize graphene, as the material is composed almost entirely of symmetric sp2 bonded carbon. After the invention of SLG significant efforts have been made to investigate phonons, electron-phonon, and electron-electron interactions in graphene using Raman sepctroscopy. Among these categories, we studied E2g phonon corrected by Landau quantizations. The phonon is predicted to have a resonant character when the phonon energy matches with the energy of asymmetric inter-LL transition energy, so-called anticrossing behavior. In graphite, we study the E2g phonon shift and broadening coupled to the inter-LL excitations at H- and K-points. Moreover, we probe a series of Raman peaks due to the symmetric inter-LL excitations over a broad magnetic eld range including including the low energy transitions involving the electron-hole mixed LL-1 and LL0 LLs, enables an accurate determination of the SWM parameters. Also, in the highest magnetic eld range (>35 T) the E2g peak narrows due to suppression of electron-phonon interaction. It allow us to determine the phonon life time through energy time conservation. More deeply, we study the temperature dependence of inter-LL excitations. Surprisingly, Raman peaks shift to the higher energy and broad with increasing the temperature. In SLG, we study magneto-phonon resonance (MPR) of E2g phonon. The interesting aspect is that the electron-phonon coupling strength depends on the lling factor and polarization of incident and scattered photons. We probe the MPR dependence on various doping level and polarizations. Moreover, we observe the surprising Raman scattering intensity in the middle of the MPR anticrossing gap. Such an unusual MPR ne structure is shown to be a result of eective mixing and splitting electron-phonon coupled modes caused by random fluctuations of strain-induced pseudo-magnetic fields. Finally, we present a Raman spectroscopy study of Bi2Se3 and Sb2Te3 crystals in the temperature range between 5 K and 300 K. We uncover a characteristic temperature dependence of the phonon peak position and linewidth, and interpret it in the context of thermal expansion and three-phonon anharmonic decay. We present experimental procedures and describe the magneto-Raman probes we built. in order to conduct these experiments. Summaries of collaborative work on magneto-elastic eects of the molecular-based magnets by using magneto-Raman spectroscopy and Aharov- Bohm oscillations of Type-II Quantum dots by using magneto-photoluminescence are given.
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Date Issued: 2012
Identifier: FSU_migr_etd-5379
Format: Thesis

Title: A Search for Exotic Mesons in γp → π+π+π−n with CLAS at Jefferson Lab.
Creator: Bookwalter, Craig, Eugenio, Paul, Plewa, Tomek, Blessing, Susan, Capstick, Simon, Crede, Volker, Department of Physics, Florida State University
Abstract/Description: In addition to ordinary q-qbar pairs, quantum chromodynamics (QCD) permits many other possibilities in meson spectra, such as gluonic hybrids, glueballs, and tetraquarks. Experimental discovery and study of these exotic states provides insight on the nonperturbative regime of QCD. Over the past twenty years, some searches for exotic mesons have met with controversial results, especially those obtained in the three-pion system. Prior theoretical work suggests that in photoproduction, gluonic...
Show moreIn addition to ordinary q-qbar pairs, quantum chromodynamics (QCD) permits many other possibilities in meson spectra, such as gluonic hybrids, glueballs, and tetraquarks. Experimental discovery and study of these exotic states provides insight on the nonperturbative regime of QCD. Over the past twenty years, some searches for exotic mesons have met with controversial results, especially those obtained in the three-pion system. Prior theoretical work suggests that in photoproduction, gluonic hybrids might be found at enhanced levels relative to that found in pion production. To that end, the E004-05 experiment at Jefferson Lab's CEBAF Large Acceptance Spectrometer (CLAS) has recently acquired a high statistics photoproduction dataset, using a liquid hydrogen target and tagged photons from a 5.71 GeV electron beam. The CLAS experimental apparatus was modified to maximize forward acceptance for peripheral production of mesons. The resulting data contain the world's largest 3π photoproduction dataset. A sample of 510K γp → π+π+π-n events have been subjected to a partial-wave analysis in search of the spin-parity exotic π1(1600) meson. Results show strong evidence for the production of the well-known nonexotic a2(1320) and π2(1670), as well as some evidence for the a1(1260). However, we find no evidence of π1(1600) production in γp → π+π+π-n. Possible explanations include misinterpretation of previous analyses claiming the existence of the π1(1600), or a preference for production mechanisms forbidden to charge-exchange photoproduction.
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Date Issued: 2012
Identifier: FSU_migr_etd-4725
Format: Thesis

Title: The Effects of Whole-Body Vibration on Cardiovascular and Autonomic Function in Overweight-Obese Premenopausal Women.
Creator: Gil, Ryan, Figueroa, Arturo, Kim, Jeong-Su, Spicer, Maria, Credé, Volker, Department of Nutrition, Food, and Exercise Science, Florida State University
Abstract/Description: Background: Being overweight or obese is associated with increased sympathetic activity and decreased vascular function which increases the cardiovascular risk. Current research has shown that conventional aerobic, resistance, and isometric exercise training has the capacity to elicit improvements in autonomic and cardiovascular function. Recently, exercise with whole-body vibration (WBV) has become of high interest to researchers in the field of exercise physiology due to its beneficial...
Show moreBackground: Being overweight or obese is associated with increased sympathetic activity and decreased vascular function which increases the cardiovascular risk. Current research has shown that conventional aerobic, resistance, and isometric exercise training has the capacity to elicit improvements in autonomic and cardiovascular function. Recently, exercise with whole-body vibration (WBV) has become of high interest to researchers in the field of exercise physiology due to its beneficial effects on bone mineral density, muscle mass, and muscle strength. Purpose: The purpose of this study was to evaluate the acute and chronic effects of WBV on arterial and cardiac autonomic function in overweight and obese (OV/OB; Body mass index 28.3 ± 0.9 kg/m2) women. Methods: In a cross over design, eight young (21 ± 2 yr) OV/OB women were randomly assigned to either WBV training (WBVT) 3 days per week or 6 weeks of no-exercise (CON). After their assigned treatment period, the subjects underwent a 4 week washout period before beginning their next 6 week treatment period (either WBVT or CON). At the beginning and end of each period, brachial blood pressure (BP), heart rate variability (HRV), augmentation index (AIx), and pulse wave velocity (PWV) were obtained at rest and 3 min after (PE3) a 4 min bout of static squat with WBV at 30 Hz frequency and 1.0 mm amplitude. Maximal strength (1-RM) was assessed for the leg extension exercise. Measurements were repeated 6 week after WBVT and CON. Results: There were significant decreases (p < 0.05) in resting systolic BP (SBP, 8 ± 5 mmHg) and diastolic BP (4 ± 2 mmHg) after WBVT compared with CON (p < 0.05). There were significant decreases (p < 0.05) in heart rate (7 ± 4 bpm), SBP (5 ± 4 mmHg), and mean arterial pressure (7 ± 3 mmHg) at PE3 after WBVT compared with CON (p < 0.05). There was a significant increase (p < 0.01) in 1-RM (12 kg) after WBVT, but not after CON. There were no changes in HRV, AIx, and PWV after both WBVT and CON. Conclusion: These preliminary data indicate that 6 weeks of WBVT elicits reductions in resting and post-exercise BP in overweight-obese women. In addition, lower post-exercise HR suggests that cardiovagal regulation may improve after WBVT. Future research is needed to further evaluate this exercise mode as a potential adjunct treatment for cardiovascular diseases.
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Date Issued: 2011
Identifier: FSU_migr_etd-4303
Format: Thesis

Title: Characterization, Fabrication, and Application of Molecularly Modified Semiconductor Nano-Devices.
Creator: Chen, Kan-Sheng, Xiong, Peng, Stiegman, Albert, Bonesteel, Nicholas, Chiorescu, Irinel, Crede, Volker, Department of Physics, Florida State University
Abstract/Description: The integration of soft (organic, biological) and hard (semiconducting, metallic) materials is of central importance in a host of emerging areas in materials research and nanoscience. Micro- and nano-scale hybrid soft/hard condensed matter structures are necessary components for such diverse applications as molecular electronics, biological and chemical sensing, directed assembly of functional nanostructures, and controlled solution-chemistry synthesis of nanomaterials. Organic molecules have...
Show moreThe integration of soft (organic, biological) and hard (semiconducting, metallic) materials is of central importance in a host of emerging areas in materials research and nanoscience. Micro- and nano-scale hybrid soft/hard condensed matter structures are necessary components for such diverse applications as molecular electronics, biological and chemical sensing, directed assembly of functional nanostructures, and controlled solution-chemistry synthesis of nanomaterials. Organic molecules have been employed not only as pathways for molecular recognition (e.g., in biosensing and directed assembly), but also as means to produce novel electronic functionality and even as active electronic components (e.g., in molecular junctions and single molecule transistors). In recent years, the scientific and engineering community has expended unprecedented effort on fundamental research in this area of nanotechnology, in hope of finding new paradigms of nanoelectronics and biomedical sensors. Inspired by this concept, this dissertation research explores the fabrication and characterization of several diverse types of solid-state/molecular hybrid nanostructures. The objectives of the research are two-fold: 1) to investigate directed self-assembly of semiconductor nano devices using molecular templates and examine molecular modification of the electronic characteristics of such devices, and 2) to study molecular functionalization of semiconductor micro/nano devices and the utilization of the functionalized devices for biomolecular sensing. Carbon nanotubes are a class of quasi-one-dimensional nanomaterials which have received extensive interest. Single-walled carbon nanotubes (SWNTs) exhibit excellent electrical properties suitable for high performance nanoelectronics. Individual SWNT field-effect transistors (FETs) have been shown to outperform state-of-the-art silicon counterparts. However, the integration of the SWNT devices into high-density architectures remains a challenge. Through the bottom-up approach, utilizing directed assembly of solvent suspended SWNTs onto a molecular template, we demonstrated the fabrication of high performance SWNT-FETs. Furthermore, selective functionalization of the metal electrodes with various polar molecules patterned by dip-pen nanolithography (DPN) gave rise to molecularly modified SWNT-FETs comprising of s-SWNT/molecule/Au heterojunction and resulted in pronounced modification to the key electrical characteristics of the SWNT-FETs, including subthreshold swing, ON/OFF ratio, and threshold voltage. By replacing the semiconducting SWNT to a metallic one, the same strategy produced m-SWNT/molecule/Au heterojunction, where the m-SWNT serves a metallic nanoprobe to study the tunneling properties of electrical current through the molecular SAM. The extraordinary precision and high spatial registry of DPN were also used to selectively functionalize active regions of micro-Hall magnetometers fabricated from an InAs quantum well heterostructures, as a necessary step towards using the μ-Hall devices for biomolecular sensing. To demonstrate detection of protein binding, the submicron molecular SAM functionalized region was subsequently attached with biotin molecules. The streptavidin coated superparamagnetic nanobeads were specifically assembled onto the biotinylated region of μ-Hall device through the biotin-streptavidin linkage and detected by the ac-phase sensitive Hall magnetometry at room temperature. The same sensing scheme was employed for label-free discrimination of a 35 base pair (bp) single strand (ss) DNA target, as a demonstration for point of care (POC) pathogenic DNA detection. An independent study of fluorescence microscopy based on arrays of mimic μ-Hall crosses showed that the platform is feasible for discriminating target DNA at a concentration of 36 pM and < 10 ppm in the presence of extraneous DNA. Binary oxide nanobelts, synthesized through a catalyst-free physical vapor deposition growth method, have emerged as a class of useful quasi-one-dimensional nanomaterials with unique "belt" like morphology. We have fabricated high-performance channel-limited SnO2 nanobelt FETs and utilized them as high sensitivity electrochemical transducers to detect various biomolecules by molecularly modifying the surface of the nanobelt with specific molecular receptors. We first demonstrated the efficacy of the sensing scheme and platform via detection of streptavidin protein using biotinylated SnO2 nanobelt FETs. The same platform was then modified to detect cardiac troponin I (cTnI) antigen, a biomedically significant marker that has been widely considered to be an effective indicator of cardiac damage upon trauma to the heart. A systematic effort was placed on optimizing and extending the capabilities of the platform. The procedures for functionalizing the oxide surface of nanobelts were modified to improve the contact transparency between the molecularly functionalized nanobelt channel and the metal electrodes to increase the yield in obtaining channel-limited SnO2 FETs for sensing applications. The versatility of the sensing scheme was finally extended by the successful attachment of DNA aptamer to the surface of the oxide nanobelts, which provides a potential general pathway to the binding of a broad variety of biomolecules, such as small molecules, proteins, nucleic acids, and even cells, tissues, and organisms. With the DNA aptamer functionalized SnO2 nanobelt FET devices, we successfully demonstrated the detection of thrombin molecules.
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Date Issued: 2011
Identifier: FSU_migr_etd-3833
Format: Thesis

Title: Measurement of the Polarization Observables I[superscript s] and I[superscript c] for rγ p → pπ⁺ π⁻ Using the CLAS Spectrometer.
Creator: Hanretty, Charles, Cred´e, Volker, Riccardi, Greg, Eugenio, Paul, Roberts, Winston, Adams, Todd, Department of Physics, Florida State University
Abstract/Description: Predictions regarding the excited baryon spectrum provided by symmetric quark models called Constituent Quark Models (CQMs) show good agreement with experimental measurements in the low-energy region (less than ≈ 1.8 GeV). The mass region above ≈ 1.8 GeV, however, contains many resonances which are predicted to exist by these models but have not been experimentally verified[1][2]. This describes a well known problem in Baryon Spectroscopy, the issue of missing resonances. These resonances are...
Show morePredictions regarding the excited baryon spectrum provided by symmetric quark models called Constituent Quark Models (CQMs) show good agreement with experimental measurements in the low-energy region (less than ≈ 1.8 GeV). The mass region above ≈ 1.8 GeV, however, contains many resonances which are predicted to exist by these models but have not been experimentally verified[1][2]. This describes a well known problem in Baryon Spectroscopy, the issue of missing resonances. These resonances are considered missing as the mass measurements made regarding these resonances are either absent or fairly large in their uncertainties[1]. This discrepancy between the theoretical predictions and the experimental measurements can be attributed to several sources. Firstly, the majority of the data regarding the excited baryon spectrum originates from pion-nucleon or kaon-nucleon scattering (which the missing resonances may only weakly couple to). Therefore, as suggested by recent quark model calculations, a study of reactions involving photoproduction (γp) may present a better opportunity for the production of these missing resonances[3]. In addition, previous analyses involved unpolarized data. This absence of polarization leads to ambiguous analysis results, therefore a constraint such as the polarization of the photons can be used in order to further constrain the kinematics of the reaction(s). The analysis of polarized photoproduction data (involving polarization of the photon and/or target) in the low-energy region (< 1.8 GeV) presents the opportunity to further study previously observed resonances, possibly resolving currently unanswered questions about their properties. An analysis of polarized photoproduction data in the high-mass region (> 1.8 GeV) allows for a study of the resonances contributions, providing insight into the issue of the missing resonances. The study of a photoproduced 3-body final state (such as γp → p π+π-) has been indicated as a promising method for detecting the effects of the missing resonances as this final state topology accounts for most of the cross section above ≈ 1 GeV. A study of double-meson final states very well may fill the holes in the experimental data as the majority of analyses regarding this issue have come from the analysis of quasi 2-body final states (such as Nπ, Nη, Nω, KΛ, and KΣ). It is also likely that these missing resonances decay to high mass intermediate states instead of directly into a meson and a ground state nucleon. Therefore the decay of these resonances is more of a chain (resulting in a two-meson-one-ground-state-nucleon state) than a direct decay. The presence (or absence) of these missing resonances can be determined through quantities sensitive to resonance contributions called polarization observables. A study of a pseudoscalar single-meson final state produced via polarized photoproduction gives access to 7 of these polarization observables. The analysis of a double-meson final state however, allows access to a total of 15 polarization observables. These additional 8 polarization observables (which are unique to a double-meson final state) arise from the more complicated kinematics needed to describe the reaction. For example, the introduction of a second meson leads gives rise to a second frame in which the two meson are produced back-to-back as well as two additional angles describing the orientation of this plane. By measuring these sensitive quantities, a determination of what resonances contribute, or do not contribute, to the excited baryon spectrum can be determined. Presented in this work are the first ever measurements of the polarization observable Is for a final state with two pions and the first ever measurements of Ic for a final state containing charged pions (let alone the first measurements of both observables for the specialized case of γp → p π+π- reactions). The presented measurements were made using the high-statistics data available in the CLAS g8b data set. This data were taken at the Thomas Jefferson National Accelerator Facility (JLab) from July 20th to September 1st of 2005 using linearly polarized photons, an unpolarized liquid hydrogen (LH2 target), and the CEBAF Large Acceptance Spectrometer (CLAS). The highly-polarized photons were produced via bremsstrahlung using an unpolarized electron beam provided by the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator and a well-oriented diamond radiator. These polarized photons were produced at five different coherent edge energies: 1.3 GeV, 1.5 GeV, 1.7 GeV, 1.9 GeV, and 2.1 GeV. Considering the 200 MeV-wide window of highly polarized photons whose upper limit is the coherent edge energy, and the five different coherent edge energies used, highly polarized photons were produced covering an total energy range of 1 GeV. These data along with the utilized analysis tools have lead to clean, continuous, low-error measurements of Is and Ic which will aide the hadronic physics community in its search for the complete description of one of the most fundamental systems in nature, the baryon. [1] U. Loring, K. Kretzschmar, B. Metsch, and H. Petry, "Relativistic quark models of baryons with instantaneous forces", Eur. Phys. J. A10, 309 (2001), hep-ph/0103287. [2] S. Capstick and N. Isgur, "Baryons in a Relativized Quark Model with Chromodynamics", Phys. Rev. D34, 2809 (1986). [3] S. Capstick and W. Roberts. Phys. Rev. D, 58:074011, 1998.
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Date Issued: 2011
Identifier: FSU_migr_etd-4283
Format: Thesis

Title: Photoproduction of ω Mesons and π⁰ω Meson Pairs off the Free Proton.
Creator: Wilson, Andrew Matthew, Crede, Volker, Sura, Philip, Eugenio, Paul, Roberts, Winston, Owens, Joseph, Department of Physics, Florida State University
Abstract/Description: The photoproduction of ω mesons and π0 ω meson pairs is studied with the intention of providing data which will be useful in isolating baryon resonances. The data used for this analysis was recorded using the CBELSA/TAPS experiment in Bonn, Germany during October-November 2002. This experiment used photons incident upon free (unbound) protons, which were contained in a liquid hydrogen target. The differential cross sections for gamma p → p ω reaction are presented for the first time by...
Show moreThe photoproduction of ω mesons and π0 ω meson pairs is studied with the intention of providing data which will be useful in isolating baryon resonances. The data used for this analysis was recorded using the CBELSA/TAPS experiment in Bonn, Germany during October-November 2002. This experiment used photons incident upon free (unbound) protons, which were contained in a liquid hydrogen target. The differential cross sections for gamma p → p ω reaction are presented for the first time by analyzing the ω meson in its radiative decay. The differential cross sections for the gamma p → p π0 ω are also presented for the first time with enough statistics and resolution to isolate baryon resonances. The initial photon energies range from threshold for each reaction to 2.5 GeV. These data show the full kinematic range of the differential cross sections for both reactions. In addition to the differential cross sections, the spin-density matrix elements have been extracted for the gamma p → p ω reaction. The unpolarized spin-density matrix elements are presented from threshold up to 2.5 GeV in initial photon energy and show remarkable agreement with previous analyses over a large angular range. Unpolarized measurements in the very forward direction are, for the first time, presented with a resolution useful for isolating baryon resonances. Also, the polarized spin-density matrix elements, ρ100 and ρ111 , are reported for the first time. These polarized elements were reported from threshold up to 1.7 GeV in initial photon energy. These spin-density matrix elements indicate the relative rate at which ω mesons are produced with a certain spin projection and will be useful in learning about the spin dynamics of the intermediate processes and any contributing baryon resonances.
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Date Issued: 2013
Identifier: FSU_migr_etd-7664
Format: Thesis

Title: Physical Properties of Magnetic As-Grown and Oxygen Annealed SnO₂: Co Thin Films.
Creator: Stoian, Graţiela M., Van Molnár, Stephan, Stiegman, Albert, Crede, Volker, Dobrosavljevic, Vladimir, Xiong, Peng, Department of Physics, Florida State University
Abstract/Description: Dilute magnetic semiconductor oxides are complex systems in which ferromagnetic and semiconducting properties coexist, potentially making these materials suitable for Spintronics applications. Understanding the fundamental physical processes taking place in these intricate materials could offer a better way to implement these structures into real life Spintronic devices. This dissertation is based on the study of the physical properties of a magnetic oxide system, namely SnO2 thin films doped...
Show moreDilute magnetic semiconductor oxides are complex systems in which ferromagnetic and semiconducting properties coexist, potentially making these materials suitable for Spintronics applications. Understanding the fundamental physical processes taking place in these intricate materials could offer a better way to implement these structures into real life Spintronic devices. This dissertation is based on the study of the physical properties of a magnetic oxide system, namely SnO2 thin films doped with a few atomic percent Co, grown by two different methods. The ultimate goal of this study is to understand the physical mechanisms of high temperature ferromagnetism (RTFM) in SnO2-δ:Co. Two different methods for growing epitaxial SnO2-δ: Co thin films were employed: pulsed laser deposition (PLD) and RF Sputtering. In both cases, films were deposited on R-cut Al2O3 substrates under well controlled growth conditions in order to produce epitaxial thin films which behave ferromagnetically at room temperature and are semiconducting. Detailed structural and magnetic characterization demonstrates that PLD SnO2-δ:Co films grown under optimal oxygen pressure are single phase SnO2 with no presence of Co-based nanoclusters in the oxide matrix. Moreover, a direct relationship between structure, resistivity and magnetization is demonstrated, the number of structural defects influencing greatly the electromagnetic properties of the studied materials. Highly crystalline samples have a larger resistivity than less ordered materials. In addition, films grown with an optimal deposition rate have a saturation magnetization that is comparable to the Co2+ low spin state (1μB/Co). This is consistent with the XPS measurements which suggest that the valence of Co in SnO2 is +2, proving that Co2+ ions substitute for octahedral Sn4+ ions in the SnO2 lattice. Temperature dependent magnetic investigations indicate the presence of a granular-type magnetism, which is believed to occur due to formation of small Co-doped SnO2 grains with different particle sizes and blocking temperatures, existing in a dielectric matrix. Annealing samples in O2 enhances the ferromagnetism dramatically due to the strong intergranular interaction produced after the thermal treatment. Electrical transport data reveal there is a hopping-type activated conduction mechanism up to room temperature. Non-diffusive electrical transport is observed up to 350 K. The study done on RF sputtered films deposited by two methods: RF co-sputtering and sputtering from a 5 at.% Co - doped target, has shown that by changing the deposition parameters, one can produce films which are highly crystalline and insulating, some of which exhibit a paramagnetic signature, originating from the presence of noninteracting Co2+ ions. It was concluded that the magnetism in sputtered SnO2:Co thin films is not carrier mediated but is due to the superexchange interaction which couples the nearest neighbor Co spins antiferromagnetically, depending on the local lattice distortions and the spin environment. The moments per Co ion in these films determined from magnetic measurements are lower than the theoretical value of low spin state Co2+ ions. Moreover, XPS and TEM analysis suggests that Sn4+ is substituted by Co2+ ions. Annealing some of the samples in oxygen environment modifies their structure and enhances the magnetic moment per Co ion. The sputtered materials studied in this project may not be suitable for Spintronics applications since magnetism is not carrier mediated due to the very low carrier concentration achieved in these samples. The deposition process was found to be unreliable because of the difficulty to control the growth. This yielded discrepancies in the structural and magnetic properties, characteristics that will be outlined in this thesis.
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Date Issued: 2013
Identifier: FSU_migr_etd-8646
Format: Thesis

Title: Extraction of the Photon Beam Asymmetry Σ in π⁰ Photoproduction off the Proton Using the CBELSA/TAPS Experiment.
Creator: Sparks, Nathan Andrew, Crede, Volker, Aldrovandi, Ettore, Eugenio, Paul, Owens, Joseph, Capstick, Simon, Department of Physics, Florida State University
Abstract/Description: The CBELSA/TAPS experiment at the electron accelerator ELSA, in Bonn, Germany, was used in order to study the photoproduction of neutral pions off the proton with a linearly polarized photon beam; Neutral pions were reconstructed through their dominant decay mode into two photons. The photons were detected in a barrel/forward electromagnetic calorimeter system which covered 99% of the 4π solid angle. The Crystal Barrel CsI(Tl) calorimeter detected photons at polar angles from 30° to 168°,...
Show moreThe CBELSA/TAPS experiment at the electron accelerator ELSA, in Bonn, Germany, was used in order to study the photoproduction of neutral pions off the proton with a linearly polarized photon beam; Neutral pions were reconstructed through their dominant decay mode into two photons. The photons were detected in a barrel/forward electromagnetic calorimeter system which covered 99% of the 4π solid angle. The Crystal Barrel CsI(Tl) calorimeter detected photons at polar angles from 30° to 168°, while TAPS, a BaF2 spectrometer, covered forward polar angles from 5.8° to 30° and served as a fast trigger; Both calorimeters had complete azimuthal angular coverage. Coherent bremsstrahlung of electrons in a diamond radiator was used to produce a linearly polarized beam of photons with a coherent peak at 1305 or 1610 MeV. The analysis of these two datasets allowed for the measurement of the photon beam asymmetry in the beam photon energy range of 920 to 1680 MeV. For the first time, these results cover the very forward polar angles of the neutral pion. The measurements are compared to the SAID, MAID, and BnGa models and to previous measurements. These new measurements of the photon beam asymmetry contribute to the ongoing experimentally-driven exploration of the N and Δ resonances. The study of strange baryons provides a link between the strong interaction physics of the excited nucleons and the heavy flavor baryons. The upcoming GlueX experiment at Jefferson Lab is expected to provide an opportunity to examine strange baryons in much greater detail than ever before. GEANT-based Monte Carlo simulations of Cascade baryons at the GlueX experiment were conducted in order to better understand the capabilities of this experiment. A proposal, "An initial study of mesons and baryons containing strange quarks with GlueX", was submitted to the 40th Jefferson Lab Program Advisory Committee (PAC), in part, supported by these Cascade baryon simulations. 200 days of additional beam time were approved, with the proposal receiving an A scientific rating.
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Date Issued: 2013
Identifier: FSU_migr_etd-8643
Format: Thesis

Title: Hadrons with Two Heavy Quarks: Symmetries, Systematics, and Spectroscopy.
Creator: Eakins, Benjamin James, Roberts, Winston, Steinbock, Oliver, Crede, Volker, Owens, Joseph, Volya, Alexander, Department of Physics, Florida State University
Abstract/Description: We explore the symmetries and systematics of the mass spectrum of hadrons with two heavy quarks. We also apply these symmetries to the strong decays of baryons with two heavy quarks. We explore the ramifications of a proposed symmetry that relates heavy diquarks to doubly heavy mesons. We present a method for determining how the excitation energy of a system containing two heavy quarks will scale as one changes the strength of the interactions and the reduced mass of the system. We use this...
Show moreWe explore the symmetries and systematics of the mass spectrum of hadrons with two heavy quarks. We also apply these symmetries to the strong decays of baryons with two heavy quarks. We explore the ramifications of a proposed symmetry that relates heavy diquarks to doubly heavy mesons. We present a method for determining how the excitation energy of a system containing two heavy quarks will scale as one changes the strength of the interactions and the reduced mass of the system. We use this to derive consequences of the heavy diquark-doubly heavy meson symmetry. We compare these consequences to the results of a quark model as well as the experimental data for doubly heavy mesons. We discuss the extension of the superflavor symmetry of Doubly Heavy Baryons (DHBs) to states which contain an excited heavy diquark, and we examine some of the consequences of this symmetry for the spectroscopy of DHBs and heavy mesons. Subsequently, we derive the consequences of this Heavy Diquark Symmetry (HDS) for the decay widths of DHBs. We compare these symmetry constraints to results from the 3P0 model for strong decays. The quark model we implement was not constructed with these symmetries and contains interactions which explicitly break HDS. Nevertheless these symmetries emerge. We argue that the 3P0 model and any other model for strong transitions which employs a spectator assumption explicitly respects HDS. We also explore the possibility of treating the strange quark as a heavy quark and apply these ideas to Ξ, Ξc, and Ξb baryons.
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Date Issued: 2013
Identifier: FSU_migr_etd-8549
Format: Thesis

Title: Search for New and Unusual Strangeonia in Photoproduction Using CLAS.
Creator: Saini, Mukesh S., Eugenio, Paul, Plewa, Tomasz, Capstick, Simon, Crede, Volker, Wahl, Horst, Weygand, Dennis, Department of Physics, Florida State University
Abstract/Description: We perform a survey of the ( proton K+ K− ), 3 charged track data taken by the CLAS detector for the HyCLAS experiment [1] during the g12 run-period at Jefferson Lab. We aim to study the strong decay amplitudes, partial widths and production channels of strangeonia from the CLAS g12 dataset. HyCLAS was motivated by the experimental results for gluonic hybrid meson candidates, theoretical Lattice QCD, and Flux-tube Model calculations and predictions. The experiment was designed and conducted...
Show moreWe perform a survey of the ( proton K+ K− ), 3 charged track data taken by the CLAS detector for the HyCLAS experiment [1] during the g12 run-period at Jefferson Lab. We aim to study the strong decay amplitudes, partial widths and production channels of strangeonia from the CLAS g12 dataset. HyCLAS was motivated by the experimental results for gluonic hybrid meson candidates, theoretical Lattice QCD, and Flux-tube Model calculations and predictions. The experiment was designed and conducted to search and observe new forms of hadronic matter through photoproduction. Crucial among the various channels explored in HyCLAS are those for strangeonia, resonances such as φ(1680), φ3 (1850) and Y(2175) [2] decaying to φ η . A meson decay via φ η is the signature that unequivocally identifies a strangeonium (s Ì) state and is the main focus of this thesis. A strangeonium decay via φ η is considered the premier decay mode to cleanly establish the strangeonia spectrum [3]. This is due to negligible interference of the φ η decay mode with the non-strange n Ì (n â {u, d}) meson decay modes, on account of the fact that φ(1020) is an almost pure s Ì vector meson and the η meson possesses a strong component of s Ì in it as well. Another analysis explored was the φ π o decay channel, which is an exotic decay mode for a meson. Decay of an initial s Ì meson via this channel is forbidden on account of the conservation of isotopic spin whereas the decay of a n Ì via the φ π o decay mode is also forbidden by the Okubo - Zweig - Iizuka (OZI) rule. Thus, observation of a resonance decaying to φ π o will provide strong evidence of mesons beyond q q , probably of a gluonic excitation - q q g or a tetraquark state - q q q q [4]. A final state of proton, K + and K − is selected from the g12 dataset. An intermediate φ state is identified by its decay to K + K − . Using Energy-Momentum conservation, missing mass in an event is calculated. Depending on the analyses, suitable missing mass cuts for the missing η mass or the π o mass is implemented to identify the particular missing particle. Invariant mass for the φ and the missing η/π o system is reconstructed to observe possible resonances. γ p → p X → p φ [η/π o ] → p K + K − [η/π o ] The yield and the cross section for the photoproduction of φ η mesons off of protons is calculated for Eγ â {4.40, 5.45} GeV/c2 using elliptical sideband subtraction. Upper and lower limits on the photoproduction cross section for possible strangeonium resonances and their subsequent decay via the φ η intermediate state are calculated using the FeldMan- Cousins approach with a 90% confidence interval limit. A partial wave analysis is also performed on the φ η intermediate state to explore for discernable resonances. The yield and the cross section for the photoproduction of φ mesons off of protons is calculated for Eγ â {4.40, 5.45} GeV/c2 . Yield is estimated for the intermediate state φ π o and its invariant mass distributions analyzed for possible resonances. The ( proton K+ K− ) final state is also explored for the rare φ ω events and the yield for the channel is measured.
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Date Issued: 2013
Identifier: FSU_migr_etd-7593
Format: Thesis

Title: Measurement of Polarization Observables in γ[over rightarrow]p[over rightarrow] → pπ⁺π⁻ Using Circular Beam and Longitudinal Target Polarization and the CLAS Spectrometer at Jefferson Laboratory.
Creator: Park, Sungkyun, Crede, Volker, Plewa, Tomasz, Eugenio, Paul, Capstick, Simon, Adams, Todd, Department of Physics, Florida State University
Abstract/Description: The study of baryon resonances offers a deeper understanding of the strong interaction, since the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c2 are generally predicted to have strong couplings to the reaction γp → pπ⁺π⁻ via πΔ or ρN intermediate states. Double-ion photo-production is, therefore, important for investigating properties of high-mass resonances. The...
Show moreThe study of baryon resonances offers a deeper understanding of the strong interaction, since the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c2 are generally predicted to have strong couplings to the reaction γp → pπ⁺π⁻ via πΔ or ρN intermediate states. Double-ion photo-production is, therefore, important for investigating properties of high-mass resonances. The excited states of the nucleon are usually found as broadly overlapping resonances, which may decay into a multitude of final states involving measons and baryons. Polarization observables make it possible to isolate single resonances from these other interference terms. The CLAS g9a (FROST) experiment, as part of the N⋆ spectroscopy program at the Jefferson Laboratory, has accumulated photoproduction data using circularly-polarized photons incident on a longitudinally-polarized butanol target in the photon energy range 0.3 to 2.4 GeV. This document summarizes how the beam-helicity asymmetry I⊙, the target asymmetry P[subscript]z, and the helicity difference P[subscript ⊙z] for the reaction γ[over rightarrow]p[over rightarrow] → pπ⁺π⁻ are extract from the g9a dataset.
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Date Issued: 2013
Identifier: FSU_migr_etd-7544
Format: Thesis

Title: Rare Exclusive Dileptonic and Radiative Decays of ΛB Baryons in Aquark Model.
Creator: Mott, Lonnie J., Roberts, Winston, Ruse, Michael, Volya, Alexander, Crede, Volker, Owens, Joseph, Department of Physics, Florida State University
Abstract/Description: Hadronic form factors for the rare weak transitions Λb→Λ(*) are calculated using a nonrelativistic quark model. The form factors are extracted in two ways. An analytic extraction using single component wave functions (SCA) with the quark current being reduced to its nonrelativistic Pauli form is employed in the first method. In the second method, the form factors are extracted numerically using the full quark model wave function (MCN) with the full relativistic form of the quark current. Both...
Show moreHadronic form factors for the rare weak transitions Λb→Λ(*) are calculated using a nonrelativistic quark model. The form factors are extracted in two ways. An analytic extraction using single component wave functions (SCA) with the quark current being reduced to its nonrelativistic Pauli form is employed in the first method. In the second method, the form factors are extracted numerically using the full quark model wave function (MCN) with the full relativistic form of the quark current. Both sets of form factors are found to satisfy the relationships expecetd from the heavy quark effective theory (HQET). Differential decay rates, branching ratios and forward-backward asymmetries (FBAs) are calculated for the dileptonic decays Λb→Λ(*)ℓ+ℓ , for transitions to both ground state and excited daughter baryons. Inclusion of the long distance contributions from charmonium resonances significantly enhances the decay rates. It is found that in the MCN model the Λ(1600) mode is the dominant mode in the μ channel when charmonium resonances are considered; the Λ(1520) mode is also found to have a comparable branching ratio to that of the ground state in the μ channel. It has been found that the FBAs for decays to Λ(1115), Λ(1600) and Λ(1405) are less sensitive to the form of the form factors in certain kinematic regions.
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Date Issued: 2011
Identifier: FSU_migr_etd-2223
Format: Thesis

Title: The Photoproduction of Strangeness in ΓP → ΛK+Π+Π− with CLAS at Jefferson Lab.
Creator: Al Ghoul, Hussein, Eugenio, Paul Michael, Justus, James, Crede, Volker, Capstick, Simon, Ostrovidov, Alexander, Wahl, Horst D., Florida State University, College of Arts and...
Show moreAl Ghoul, Hussein, Eugenio, Paul Michael, Justus, James, Crede, Volker, Capstick, Simon, Ostrovidov, Alexander, Wahl, Horst D., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: The available information about strange excited mesons is limited and most of the observed states have been reported but not confirmed. While the low mass region (1.0 - 1.5 GeV) has been extensively studied in the past and states such as the K1(1270), K1(1400), and K*(1410) have been confirmed by a handful of experiments, little is known about the spin-parity structure of resonances in the higher K+ π+ π- mass region (1.5-2.0 GeV). Past experiments have used hadron beams to gain access to the...
Show moreThe available information about strange excited mesons is limited and most of the observed states have been reported but not confirmed. While the low mass region (1.0 - 1.5 GeV) has been extensively studied in the past and states such as the K1(1270), K1(1400), and K*(1410) have been confirmed by a handful of experiments, little is known about the spin-parity structure of resonances in the higher K+ π+ π- mass region (1.5-2.0 GeV). Past experiments have used hadron beams to gain access to the K+ π+ π- system, and have provided extensive information about strange states that made mapping their spectrum possible. Except for the K*(892), none of the excited strange states has been photoproduced before. We perform a partial wave analysis on a photoproduced K+ π+ π- system produced off a Λ baryon using the CLAS detector at Jefferson Lab. Using a photon beam incident of a liquid hydrogen target, we are able to reconstruct 16K events of the γ p -> Λ K+ π+ π- topology. Results from initial data selection confirmed the dominance of two decay modes for a K+ π+ π- resonance: the K*(892)π+ and the ρ(770)K+. A PWA was carried out in the helicity formalism using the reflectivity basis in the isobar model to parametrize the decay amplitudes of the resonances. Resonating structures are found in the 1+S wave primarily coupling to K*(892)π+ with a mass of 1.35 GeV/c2 and to ρ(770)K with a lower mass structure around 1.33 GeV/c2 and a higher mass resonance around 1.73 GeV/c2. The 1-P also exhibited a significant resonating behavior with a mass of 1.43 GeV/c2 coupling primarily to the K*(892)π+ decay mode. Also observed, an enhancement around 1.49 GeV/c2 in the 2+D wave strongly coupling to K*2 (1430)π+, and an enhancement in the 2-S wave around 1.76 GeV/c2 coupling primarily to K*2 (1430)π+.
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Date Issued: 2016
Identifier: FSU_2016SP_AlGhoul_fsu_0071E_13108
Format: Thesis

Title: Relativistic Mean Field Models for Finite Nuclei and Neutron Stars.
Creator: Chen, Wei-Chia, Piekarewicz, Jorge, Kopriva, David A., Volya, Alexander, Credé, Volker, Bonesteel, N. E., Florida State University, College of Arts and Sciences, Department of...
Show moreChen, Wei-Chia, Piekarewicz, Jorge, Kopriva, David A., Volya, Alexander, Credé, Volker, Bonesteel, N. E., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: In this dissertation we have created theoretical models for finite nuclei, nuclear matter, and neutron stars within the framework of relativistic mean field (RMF) theory, and we have used these models to investigate the elusive isovector sector and related physics, in particular, the neutron-skin thickness of heavy nuclei, the nuclear symmetry energy, and the properties of neutron stars. To build RMF models that incorporate collective excitations in finite nuclei in addition to their ground...
Show moreIn this dissertation we have created theoretical models for finite nuclei, nuclear matter, and neutron stars within the framework of relativistic mean field (RMF) theory, and we have used these models to investigate the elusive isovector sector and related physics, in particular, the neutron-skin thickness of heavy nuclei, the nuclear symmetry energy, and the properties of neutron stars. To build RMF models that incorporate collective excitations in finite nuclei in addition to their ground-state properties, we have extended the non-relativistic sum rule approach to the relativistic domain. This allows an efficient estimate of giant monopole energies. Moreover, we have combined an exact shell-model-like approach with the mean-field calculation to describe pairing correlations in open-shell nuclei. All the ingredients were then put together to establish the calibration scheme. We have also extended the transformation between model parameters and pseudo data of nuclear matter within the RMF context. Performing calibration in this pseudo data space can not only facilitate the searching algorithm but also make the pseudo data genuine model predictions. This calibration scheme is also supplemented by a covariance analysis enabling us to extract the information content of a model, including theoretical uncertainties and correlation coefficients. A series of RMF models subject to the same isoscalar constraints but one differing isovector assumption were then created using this calibration scheme. By comparing their predictions of the nuclear matter equation of state to both experimental and theoretical constraints, we found that a small neutron skin of about 0.16 fm in Pb208 is favored, indicating that the symmetry energy should be soft. To obtain stronger evidence, we proceeded to examine the evolution of the isotopic chains in both oxygen and calcium. Again, it was found that the model with such small neutron skin and soft symmetry energy can best describe both isotopic chains, and the resultant values of the neutron-skin thickness and the symmetry energy are consistent with most current constraints. Finally, we addressed the recent tension between dense matter theory and the observation of neutron stars with rather small stellar radii. By employing Lindblom's algorithm, we were able to derive the underlying equation of state for assumed mass-radius relations having the "common radius" feature followed by recent analyses. We found that, in order to support two-solar-mass neutron stars, the typical stellar radii must be greater than 10.7 km—barely compatible with recent analyses—to prevent the underlying equation of state from violating causality.
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Date Issued: 2015
Identifier: FSU_2015fall_Chen_fsu_0071E_12869
Format: Thesis

Title: The Search for N* Resonances: Measurement of Differential Cross Sections and Polarization Observables for γp → pω and γp → K0Σ+ Using Circularly-Polarized Photons at CLAS, Jefferson Lab.
Creator: Akbar, Zulkaida, Crede, Volker, Meyer-Bäse, Anke, Piekarewicz, Jorge, Eugenio, Paul Michael, Adams, Todd, Florida State University, College of Arts and Sciences, Department of...
Show moreAkbar, Zulkaida, Crede, Volker, Meyer-Bäse, Anke, Piekarewicz, Jorge, Eugenio, Paul Michael, Adams, Todd, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: The study of baryon resonances offers a deeper understanding of the strong interaction, since the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of these states. The baryon resonances have been fairly accurately predicted in the low-energy region by constituent quark models and lattice quantum chromodynamics. However, most of the predicted higher-lying excited resonances (center-of-mass energies above 1.7 GeV/c²) and experimental findings do not...
Show moreThe study of baryon resonances offers a deeper understanding of the strong interaction, since the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of these states. The baryon resonances have been fairly accurately predicted in the low-energy region by constituent quark models and lattice quantum chromodynamics. However, most of the predicted higher-lying excited resonances (center-of-mass energies above 1.7 GeV/c²) and experimental findings do not match up. The model calculations predict more baryon resonances than have been experimentally observed. Quark model calculations have suggested that some of the unobserved resonances couple strongly to γp reactions. The higher-lying excited are also generally predicted to have strong couplings to final states involving a heavier meson, e.g. one of the vector mesons, ρ, ω, ϕ. The excited states of the nucleon are usually found as broadly overlapping resonances, which may decay into a multitude of finasl states involving mesons and baryons. Polarization observables make it possible to isolate singleresonance contributions from other interference terms. This works presents measurements of the helicity asymmetry, E, for the reaction γp → pω in the energy range 1.1 GeV < Eγ < 2.3 GeV, differential cross sections, and spin density matrix elements, also for the reaction γp → pω in the energy range 1.5 GeV < Eγ < 5.4 GeV. Photoproduction of nucleon resonances in their decay to strange particles also offers attractive possibilities because the strange quark in the particle generates another degree of freedom and gives additional information not available from the nucleon-nucleon scattering. Thus, we have also extracted the helicity asymmetry, E, for the reaction γp → K⁰Σ⁺ in the energy range 1.1 GeV < Eγ < 2.1 GeV, differential cross sections, and recoil hyperon polarization, P, also for the reaction γp → K⁰Σ⁺ in the energy range 1.15 GeV < Eγ < 3.0 GeV. The data were collected at Jefferson Lab, using the CLAS detector, as part of the g9a and g12 experiments. Both experiments, as part of the N* spectroscopy program at Jefferson Laboratory, accumulated photoproduction data using circularly-polarized photons incident on a longitudinally-polarized butanol target in the g9a experiment and un-polarized liquid hydrogen target for the g12 experiment. A partial-wave analysis to the E data for the reaction γp → pω within the Bonn-Gatchina framework found dominant contributions from the 3/2⁺ near threshold, which is identified with the sub-treshold N(1720)3/2⁺ resonance. Some additional resonances and the t-channel π and pomeron exchange are needed to describe the data.
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Date Issued: 2018
Identifier: 2018_Su_Akbar_fsu_0071E_14714
Format: Thesis

Title: Spin Transport in Silicon Nanowires with an Intrinsic Axial Doping Gradient.
Creator: Kountouriotis, Konstantinos, Xiong, Peng, Lenhert, Steven John, Hill, S., Crede, Volker, Schlottmann, Pedro U., Florida State University, College of Arts and Sciences,...
Show moreKountouriotis, Konstantinos, Xiong, Peng, Lenhert, Steven John, Hill, S., Crede, Volker, Schlottmann, Pedro U., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: This dissertation is focused on electrical spin injection and detection at the nanoscale dimensions that semiconductor nanowires offer. Semiconductor spintronics is the natural extension of metallic spintronics for applications in semiconductor industry. After the tremendous impact of the giant magnetoresistance effect (GMR) in hard disk read heads, semiconductor spintronics has been thought as the key ingredient for the realization of spin field-effect transistors (Spin-FETs). The advantages...
Show moreThis dissertation is focused on electrical spin injection and detection at the nanoscale dimensions that semiconductor nanowires offer. Semiconductor spintronics is the natural extension of metallic spintronics for applications in semiconductor industry. After the tremendous impact of the giant magnetoresistance effect (GMR) in hard disk read heads, semiconductor spintronics has been thought as the key ingredient for the realization of spin field-effect transistors (Spin-FETs). The advantages of spintronic devices would include non-volatility, enhanced data processing speeds, decreased electric power consumption and facilitation of quantum computation. The primary goal of this research is to study spin dynamics and spin-polarized transport in semiconductor nanowire (NW) channels, specifically in phosphorus (P) doped silicon (Si) nanowires (NWs). The interest in one-dimensional (1D) nanoscopic devices is driven by the rich spin-dependent physics quantum confinement engenders, and the eventual miniaturization of the spintronic devices down to nanoscales. One of the most important aspects to achieve efficient spin injection from a ferromagnet (FM) into a semiconductor (SC) is the interface between the two materials. This study is focused primarily on this effect and how it can be tuned. In this work, we peform systematic spin transport measurements on a unique type of P-doped Si NWs which exhibit an inherent doping gradient along the axial direction. On a single NW, we place a series of FM electrodes, which form contacts that evolve from Ohmic-like to Schottky barriers of increasing heights and widths due to the pronounced doping gradient. This facilitates rigorous investigation of the dependence of the spin signal on the nature of the FM/SC interface. The advantage of using a single NW to study the afformentioned effects is that possible complications during the fabrication process are minimized compared to experiments that use multiple different devices to perform such experiments. 2-terminal (2T), nonlocal 4-terminal (4T) and 3-terminal (3T) spin valve (SV) measurements using different configurations of FM electrodes were performed on the Si NWs. In addition, 3T and nonlocal 4T Hanle measurements were performed. The collected data reveal distinct correlations between the spin signals and the injector and detector interfacial properties. These results were possible due to the unique inhomogeneous doping profile of our Si NWs. This study reveals a distinct correlation between the spin signals and the FM/Si NW injector interfacial properties. Specifically, we observe a decreasing injected current spin polarization due to diminishing contribution of the d-electrons, thus the necessary tunneling contact for efficient spin injection and its properties are being investigated and analyzed. The results demonstrate that there is an optimal window of interface resistance parameters for maximum injected current spin polarization. In addition, they suggest a new approach for maximizing the spin signals by making devices with asymmetric interfaces. To the best of our knowledge, this is the first report of electrical spin injection in SC channels with asymmetric interfaces.
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Date Issued: 2018
Identifier: 2018_Su_Kountouriotis_fsu_0071E_14593
Format: Thesis

Title: Search for New and Unusual Strangeonia States Using γp → pφη with GlueX at Thomas Jefferson National Accelerator Facility.
Creator: Cannon, Bradford Emerson, Eugenio, Paul Michael, Aldrovandi, Ettore, Capstick, Simon, Wahl, Horst, Crede, Volker, Ostrovidov, Alexander, Florida State University, College of...
Show moreCannon, Bradford Emerson, Eugenio, Paul Michael, Aldrovandi, Ettore, Capstick, Simon, Wahl, Horst, Crede, Volker, Ostrovidov, Alexander, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: We perform an analysis dedicated to the search for new and unusual strangeonium states produced in the reaction γp → pφη. The data used for this analysis was recorded during the Spring 2017 physics run for Hall D of Thomas Jefferson National Accelerator Facility, where the GlueX experiment is located. The GlueX experiment uses a linearly polarized coherent bremsstrahlung beam of up to 12 GeV in energy. This photon beam interacts with a stationary liquid hydrogen target located inside the...
Show moreWe perform an analysis dedicated to the search for new and unusual strangeonium states produced in the reaction γp → pφη. The data used for this analysis was recorded during the Spring 2017 physics run for Hall D of Thomas Jefferson National Accelerator Facility, where the GlueX experiment is located. The GlueX experiment uses a linearly polarized coherent bremsstrahlung beam of up to 12 GeV in energy. This photon beam interacts with a stationary liquid hydrogen target located inside the GlueX detector. The subsequent photoproduction will provide final states ideal for studying both exotic and non-exotic ss ̄ mesons. After all cuts, a total of four different selection methods were used to study the φη parent state. Three of these methods used an event by event probabilistic weighting method in order to separate signal from background, and the fourth method was simply an elliptical subtraction which did not utilize probabilistic weighting. After comparing the φη invariant mass spectra for all selection methods, two structures were consistently observed. One of the structures was found to have a mass of (m = 1.657 ± 0.008)GeV/c^2 and a width of (σ = 0.190 ± 0.024)GeV/^2 ; and the second structure was found to have a mass of (m = 1.879 ± 0.004)GeV/c^2 and a width of (σ = 0.042 ± 0.014)GeV/c^2 .
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Date Issued: 2019
Identifier: 2019_Spring_Cannon_fsu_0071E_15063
Format: Thesis

Title: Magnetoelectric and Multiferroic Properties in Layered 3D Transition Metal Oxides.
Creator: Hwang, Jungmin, Choi, Eun Sang, Schlottmann, Pedro, Dalal, Naresh S., Brooks, James S., Credé, Volker, Zhou, Haidong, Department of Physics, Florida State University
Abstract/Description: Functional ferroelectric and magnetic materials have played an important role of modern technology in the sensor or storage device industries. Ferroelectricity and ferromagnetism emerge from different origins. However, it is discovered that these two seemingly unrelated phenomena can actually coexist in materials called multiferroics. Since current trends toward device miniaturization have increased interests in combining electronic and magnetic properies into multifunctional materials,...
Show moreFunctional ferroelectric and magnetic materials have played an important role of modern technology in the sensor or storage device industries. Ferroelectricity and ferromagnetism emerge from different origins. However, it is discovered that these two seemingly unrelated phenomena can actually coexist in materials called multiferroics. Since current trends toward device miniaturization have increased interests in combining electronic and magnetic properies into multifunctional materials, multiferroics have attracted great attention. Ferromagnetic ferroelectric multiferroics are especially fascinating not only because they have both ferroic properties, but also because of the magnetoelectric coupling which leads the interaction between the magnetic and electric polarization. Recent theoretical breakthroughs in understanding the coexistence of magnetic and electrical ordering have regenerated a great interests in research of such magnetoelectric multiferroics. The long-sought control of electric polarization by magneticfields was recently discovered in `frustrated magnets', for example the perovskites RMnO3, RMn2O5 (R: rare earth elements), Ni3V2O8, delafossite CuFeO2, spinel CoCr2O4, MnWO4, etc. In this dissertation, I have explored several magnetoelectric materials and multiferroics, which show significant magnetoelectric interactions between electric and magnetic orderings. The objects of my projects are focused on understanding the origins of such magnetoelectric couplings and establishing the magnetic/electric phase diagrams and the spin structures. I believe that my works would help to understand the mechanisms of magnetoelectric effects and multiferroics.
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Date Issued: 2012
Identifier: FSU_migr_etd-5367
Format: Thesis

Title: Dielectric and Conducting Properties of the Spinel Structures FeV₂O₂, MnV₂O₂ and CoV₂O₂ in High Magnetic Field and under Very High Pressure.
Creator: Kismarahardja, Ade Wijaya, Brooks, James S., Zhang, Mei, Dobrosavljevic, Vladimir, Xiong, Peng, Credé, Volker, Department of Physics, Florida State University
Abstract/Description: It is always very nice when a new discovery found in an old material. The spinel vanadate has become one of the hot topics in the condensed matter physics both experimentally and theoretically. It shows many interesting behaviors due to the interaction among spin, orbital and lattice degrees of freedom. The AV2O4 structure with A is a transition metal ion (Fe2+, Mn2+ and Co2+) exhibits several structural transitions and a magnetic ordering from paramagnetic to ferrimagnetic. Some theoretical...
Show moreIt is always very nice when a new discovery found in an old material. The spinel vanadate has become one of the hot topics in the condensed matter physics both experimentally and theoretically. It shows many interesting behaviors due to the interaction among spin, orbital and lattice degrees of freedom. The AV2O4 structure with A is a transition metal ion (Fe2+, Mn2+ and Co2+) exhibits several structural transitions and a magnetic ordering from paramagnetic to ferrimagnetic. Some theoretical approaches have been made in order to explain the physics of spinels. There are four main factors that contribute to the complexity of spinel system, e.g, spin, orbital, crystal structure and charge. Kugel and Khomskii first proposed a physical model combining spin and orbit degrees of freedom followed by Tsunetsugu and Motome who combined the super exchange and Jahn-Teller effect[2,3]. On the other hand, Tchernyshyov proposed a physical model based on the interplay of spin, orbital and Jahn-Teller effect[4]. Many discoveries from the experiments were also found in this type of material; memory effect in the polycrystal FeV2O4[5], the magnetic switching of the crystal structure in MnV2O4[7] and the magnetic structure of MnV2O4 using neutron study[7]. The modern techniques of x-ray and neutron scattering have brought important knowledge of the crystal and its magnetic structure. However, these techniques require a very good apparatus and a very high accuracy. I used much simpler technique to examine the physical properties of single crystals FeV2O4, MnV2O4 and CoV2O4. Firstly, I did the capacitance and dissipation measurements in high magnetic field on single crystals FeV2O4, MnV2O4 and CoV2O4 in our laboratory (NHMFL) at Tallahassee, Florida and secondly, I did the electrical transport measurements under very high pressure on single crystals FeV2O4 and CoV2O4 in Institute for Solid State Physics (ISSP), the University of Tokyo, Japan. Single crystals MnV2O4 and FeV2O4 are insulators and their resistivity can be higher than 200 Ω cm at room temperature but single crystal CoV2O4 is a semiconductor with the resistivity is around 60 x 10-3 Ω cm at room temperature. However, these single crystals become more insulating at low temperatures so the capacitance measurement is a good tool to investigate their electrical properties. It turned out that the capacitance and dissipation measurements in high magnetic field were very interesting measurements in order to study the interaction between the spin, orbital and lattice in these spinels. The capacitance of a material is related to the dielectric constant and also the geometrical factors of the material, i.e, the distance between the electrodes and the area of the electrodes. In addition, the magnetic field creates magnetostriction effect that changes the dimension of crystal. This situation can be very interesting in order to investigate dielectric properties of these compounds in high magnetic field. FeV2O4, MnV2O4 and CoV2O4 have a magnetic ordering from paramagnetic to ferrimagnetic at 110 K, 56 K and 152 K respectively. Furthermore, the interaction between the tetrahedral site and the octahedral site in the spinel structure also creates structural distortions. I observed the changes of the crystal structure in single crystal FeV2O4 by measuring the capacitance and dissipation under high magnetic field. I discovered that there was a significant amount of heat released at low temperature as the magnetic moment changes its orientation. This effect was observed from a sharp peak in the temperature, the capacitance and the dissipation versus magnetic field data at the field where the magnetic moment changes its orientation. This was not observed in the previous measurements on polycrystal FeV2O4 done by Takei, et al.[5] and in the field dependence of capacitance of the other spinels, MnV2O4 and CoV2O4. Moreover, from the magnetization and capacitance measurements on single crystal FeV2O4, a small plateau at low temperature was observed in the vicinity of 0 Tesla. This is the evidence that there are two magnetic moments exist in single crystal FeV2O4. In single crystal MnV2O4, I also observed the changes of the crystal structure and the magnetic ordering. I applied the magnetic field at different temperatures and measured the capacitance and dissipation of single crystal MnV2O4. From the field dependence of the capacitance and dissipation of single crystal MnV2O4, I confirmed that there is a structural transition at 52 K and a magnetic ordering at 56 K. However, at low temperature, the field dependence of the capacitance of single crystal MnV2O4 behaves differently compared to FeV2O4. This is most likely due to the ratio between lattice constant c in tetragonal phase and lattice constant a in cubic phase, ct/ac . For single crystal FeV2O4 ct/ac, > 1, but ct/ac < 1 for single crystal MnV2O4. The third one, single crystal CoV2O4, is the most conducting among three spinels and I could not measure the capacitance from room temperature down to 30 K. However, below 30 K this crystal becomes more insulating and I could measure its capacitance. As I swept the field below 10 K, the field dependence of the dielectric constant showed a time dependent behavior. Moreover, I observed a dipole like behavior in single crystal CoV2O4 although it was not very pronounced. Another good tool to probe the electrical properties of spinels is the resistivity measurement under very high pressure. I did resistivity measurements on single crystals CoV2O4 and FeV2O4 under very high pressure up to 8 GPa using cubic anvil system in ISSP. In general, the resistivity of these compounds decreased with increasing pressure. I could not observe the magnetic ordering of FeV2O4 under ambient pressure because it was very insulating. The magnetic ordering could be observed above 2 GPa and the magnetic ordering temperature increased linearly with increasing pressure. The effect was similar with CoV2O4. More interestingly, CoV2O4 showed a metallic behavior and a metal to insulator transition under high pressure. This is a new observation in this type of material. The interesting aspect of spinel vanadate is that the system approaches the itinerant electron limit with decreasing distance between vanadium ions. J.B Goodenough predicted a critical distance between vanadium ions in the spinel vanadate system, 2.94 Å. If the distance between vanadium ions (V-V distance) is smaller than this critical distance, the system becomes metallic. The V-V distance of single crystal CoV2O4 is close to this critical value. The resistivity data of single crystal CoV2O4 under very high pressure confirmed that CoV2O4 is sitting at the boundary between the insulator and the metal regime. Finally, Variable Range Hopping (VRH) model and Arrhenius model were used to fit the resistivity data of single crystals FeV2O4 and CoV2O4. I found that the energy barrier parameter T0 and the activation energy Ea decreased with increasing pressure.
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Date Issued: 2010
Identifier: FSU_migr_etd-2882
Format: Thesis

Title: A Novel Stochastic Poisson-Boltzmann Solver and incorporation of Finite Ion Sizes.
Creator: Silalahi, Alexander R. J., Piekarewicz, Jorge, Fenley, Marcia O., Mascagni, Michael, Van Winkle, David, Crede, Volker, Department of Physics, Florida State University
Abstract/Description: Electrostatic interactions play an important role in many aspects of the structural and functional properties of biomolecules because of their long-range behavior. The nonlinear Poisson-Boltzmann equation (NLPBE) theory has long been used as a standard tool for modeling non-specific electrostatic interactions of biomolecules in aqueous salt solution. In the NLPBE framework, ions are treated as point-like charged particles and their size effects are neglected. A major contribution in this...
Show moreElectrostatic interactions play an important role in many aspects of the structural and functional properties of biomolecules because of their long-range behavior. The nonlinear Poisson-Boltzmann equation (NLPBE) theory has long been used as a standard tool for modeling non-specific electrostatic interactions of biomolecules in aqueous salt solution. In the NLPBE framework, ions are treated as point-like charged particles and their size effects are neglected. A major contribution in this dissertation is the incorporation of the ion sizes effect into the NLPBE framework. In this dissertation we developed a non-uniform ion size modified Poisson-Boltzmann equation (SMPBE) to study the distribution of ions around an A-form ribonucleic acid (RNA) duplex and compare it with predictions obtained with molecular dynamics (MD) simulations. We showed that the ion distribution profiles of a 25-mer RNA duplex in aqueous 1:1 salt solution computed with the two approaches agree quite well with each other. However, the predictions of ionic profiles for a 25-mer RNA duplex obtained with MD simulations and the non-uniform ion SMPBE approach developed in as part of this thesis differ when multivalent ions are present in the aqueous ionic solution, potentially due to site bound ions and/or ion-ion correlations. We also modified a stochastic-based numerical method to solve the linear Poisson-Boltzmann equation (LPBE) simultaenoulsy at multiple salt concentrations using a single Monte Carlo (MC) Poisson-Boltzmann run. We showed that by using this method, the salt dependence of the electrostatic solvation free energy and the electrostatic potential can be computed to arbitrary accuracy. We then used this stochastic approach to compute Born radii of a biomolecule.
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Date Issued: 2011
Identifier: FSU_migr_etd-1730
Format: Thesis

Title: Physical and Chemical Pressure Effects on Magnetic Spinels.
Creator: Kiswandhi, Andhika O., Zhou, Haidong, Dobrosavljević, Vladimir, Siegrist, Theo M., Beekman, Christianne, Credé, Volker, Florida State University, College of Arts and Sciences,...
Show moreKiswandhi, Andhika O., Zhou, Haidong, Dobrosavljević, Vladimir, Siegrist, Theo M., Beekman, Christianne, Credé, Volker, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: Transition metal oxides and chalcogenides have been the major focus of studies in condensed matter physics. The complexity of the system, involving spin and orbital effects, as well as lattice degree of freedom, makes them intriguing subjects not only because of these individual effects, but also the effects due to the interaction among them. In AB2X4 materials (A = Mn2+, Co2+, Fe2+; B = V3+, Cr3+; X = O2-, S2-) which crystallize in spinel structure (space group F d -3 m), these effects and...
Show moreTransition metal oxides and chalcogenides have been the major focus of studies in condensed matter physics. The complexity of the system, involving spin and orbital effects, as well as lattice degree of freedom, makes them intriguing subjects not only because of these individual effects, but also the effects due to the interaction among them. In AB2X4 materials (A = Mn2+, Co2+, Fe2+; B = V3+, Cr3+; X = O2-, S2-) which crystallize in spinel structure (space group F d -3 m), these effects and their interactions manifest in their transport properties, magnetic ordering, itinerant electron magnetism, structural distortion, and geometrical frustration effect due to the antiferromagnetically coupled B-sites. These effects are dependent on the distance between the interacting cations, which can be varied by chemical substitution or pressure. The main objective of this dissertation is to study the physical properties of Mott-insulator spinels in approaching their critical inter-cationic distances where an insulator-metal transition occurs. Studying the insulator-metal transition in Mott insulators is important in advancing our understanding, especially in the field of fundamental physics and materials engineering, on the intricate relationships between the transport and magnetic properties and the emergence of new behaviors that arise from such properties in these materials. In this dissertation, the behavior of the physical properties of Mn1-xCoxV2O4, AV2O4 (A = Cd, Mg, Zn), and the transport properties of FeCr2S4 in approaching the insulator-metal transition are reported. Mn1-xCoxV2O4, AV2O4, and FeCr2S4 are chosen for this study due to their dominant V-V or Cr-Cr interactions, which are responsible for their transport properties. In Mn1-xCoxV2O4, the vanadium-vanadium distance is varied by means of chemical pressure (chemical substitution) to bring the system closer to the itinerant electron limit given by the critical V-V distance of 2.94 Å. In Mn1-xCoxV2O4, the structural distortion temperature and transport activation energy decreases with decreasing V-V distance, while the magnetic ordering temperature increases. The results of the transport and structural studies are in agreement with the critical V-V distance scenario of electronic delocalization. Next, a comparative structural study on AV2O4 with non-magnetic A-site ions (A = Cd, Mg, Zn) and Mn1-xCoxV2O4 is also reported. The study indicates that while the V-V interactions are dominant, the A-site ions and their magnetism produce a considerable effect on the passage from the localized to delocalized electron limit. This is proven by the two paths that emerge in the V-V distance dependence of the transport and structural properties where one path includes only the AV2O4, whereas the other includes only Mn1-xCoxV2O4. The transport property of FeCr2S4 under high pressure was also studied. Due to the t2g electronic configuration of Cr3+, the Cr-Cr interaction is also dominant. A high pressure measurement using a cubic anvil press up to 8 GPa was performed to induce an insulator-metal transition. The decrease in the Cr-Cr distance with increasing hydrostatic pressure was confirmed by x-ray diffraction measurements. The Bloch parameter of FeCr2S4 was found to be -2.4, which suggests that FeCr2S4 lies in the localized regime. The high pressure transport measurement on FeCr2S4 shows a decrease in the activation energy and an increase in the magnetic transition temperature with increasing hydrostatic pressure. An insulator to metal transition was observed at a pressure of 7.5 GPa with a possible onset at 7 GPa, at which the Cr-Cr distance is 3.44 Å. In the case of Cr-oxides, it was predicted that the critical Cr-Cr distance is 2.84 Å, but it should be higher for a less electronegative anion. Therefore, the difference in the anion species is responsible for the difference of 0.6 Å between the critical Cr-Cr distance in oxides and the actual Cr-Cr distance where the insulator-metal transition occurs. The insulator-metal transition is followed by a structural transformation at P = 8 GPa.
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Date Issued: 2014
Identifier: FSU_migr_etd-9201
Format: Thesis

Title: A Study of Nuclear Structure and Neutron Stars with a Bayesian Neural Network Approach.
Creator: Utama, Raditya, Piekarewicz, Jorge, Mio, Washington, Prosper, Harrison B., Capstick, Simon, Crede, Volker, Florida State University, College of Arts and Sciences, Department of...
Show moreUtama, Raditya, Piekarewicz, Jorge, Mio, Washington, Prosper, Harrison B., Capstick, Simon, Crede, Volker, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: In this dissertation, we introduce a new approach in building a hybrid nuclear model that combines some existing theoretical models and a \universal" approximator. The goal of such an approach is to obtain new predictions of nuclear masses and charge radii. We begin our study by investigating nuclear masses based on theoretical and experimental values. Nuclear masses are essential for astrophysical applications, such as r-process nucleosynthesis and neutron-star structure. To overcome the...
Show moreIn this dissertation, we introduce a new approach in building a hybrid nuclear model that combines some existing theoretical models and a \universal" approximator. The goal of such an approach is to obtain new predictions of nuclear masses and charge radii. We begin our study by investigating nuclear masses based on theoretical and experimental values. Nuclear masses are essential for astrophysical applications, such as r-process nucleosynthesis and neutron-star structure. To overcome the intrinsic limitations of the existing ``state-of-the-art" mass models, a renement is generated based on a Bayesian Neural Network (BNN) formalism. A novel BNN approach is applied with the aim of optimizing mass residuals between theory and experiment. A signicant improvement (of about 40%) in the mass predictions of existing models is obtained after BNN renement. Moreover, these improved results are accompanied by proper statistical errors. By constructing a \world average" of these predictions, we obtained a unied mass model that is used to predict the composition of the outer crust of a neutron star. In order to get a better description of nuclear structure, a similar procedure is also implemented in the nuclear charge radius. A class of relativistic energy density functionals is used to provide robust predictions for nuclear charge radii. In turn, these predictions are rened through the BNN approach to generate predictions for the charge radii of thousands of nuclei throughout the nuclear chart. The neural networks function is trained using charge radii residuals between theoretical predictions and experimental data. Although the predictions obtained with density functional theory provide a fairly good description of the experiment, our results show signicant improvement (better than 40%) after BNN renement. Despite the improvement and robust predictions, we failed to uncover the underlying physics behind the intriguing behavior of charge radii along the calcium isotopic chain. Overall, we have successfully demonstrated the ability of the BNN approach to signicantly increase the accuracy of nuclear models in the predictions of nuclear masses and charge radii. Extension to other nuclear observables is a natural next step in asserting the eectiveness of the BNN method in nuclear physics.
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Date Issued: 2016
Identifier: FSU_FA2016_Utama_fsu_0071E_13557
Format: Thesis

Title: A Dalitz Plot Analysis and Extraction of Spin Density Matrix Elements for the Ω → 3Π Decay.
Creator: Zeoli, Christopher Paul, Crede, Volker, Sura, Philip, Eugenio, Paul Michael, Roberts, Winston, Adams, Todd, Florida State University, College of Arts and Sciences, Department of...
Show moreZeoli, Christopher Paul, Crede, Volker, Sura, Philip, Eugenio, Paul Michael, Roberts, Winston, Adams, Todd, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: At the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson National Laboratory (JLab), $\omega$ vector-mesons were photo-produced off a fixed, liquid-hydrogen target during the 2009 run-period via the reaction $\gamma p \rightarrow p \omega$. The charged final-state particles from the $\omega$~resonance decays were detected by the CEBAF Large Acceptance Spectrometer (CLAS). With a combination of measurements which involved the use of time and energy-deposit counters as well as...
Show moreAt the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson National Laboratory (JLab), $\omega$ vector-mesons were photo-produced off a fixed, liquid-hydrogen target during the 2009 run-period via the reaction $\gamma p \rightarrow p \omega$. The charged final-state particles from the $\omega$~resonance decays were detected by the CEBAF Large Acceptance Spectrometer (CLAS). With a combination of measurements which involved the use of time and energy-deposit counters as well as reconstructed drift chamber (DC) tracks, the 4-momenta and vertices of the initial- and charged final-state particles were determined. Subsequent to reconstruction, event selection, kinematic fitting, signal and background separation, and detector efficiency simulation of the data for the three-pion final-state, i.e. $\omega \rightarrow \pi^+~\pi^-~(\pi^0)$, the Florida State University (FSU) Experimental Hadronic Nuclear Group has extracted the differential production cross section.\\ \indent With such data and the measured differential cross section in hand, I have conducted a Dalitz plot analysis of the $\omega \rightarrow 3\pi$ decay in close cooperation with the Joint Physics Analysis Center (JPAC) at JLab. The decay probability density separates into angle-dependent and -independent factors: the Spin Density Distribution (SDD) which is proportional to the differential cross section, and the reduced decay distribution (RDD) which is proportional to the decay width, respectively. The Spin Density Matrix Elements (SDMEs) for an unpolarized beam were obtained from fitting the SDD. In addition, fits for two different RDDs, i.e. a Dalitz plot distribution and a JPAC distribution, have been underway. The former is a truncated polynomial expansion of Lorentz Invariant Dalitz plot variables. The latter was based on the isobar model of the $\omega$ decay. Having made use of sub-energy unitarity, this model accounts for both elastic and inelastic 3-body re-scattering effects. Plus, fitting this model to measured data is a first. A comparison through fit parameters of each reduced distribution is intended. Lastly, my results and as well as a discussion of future extensions to this study and the prospects for similar light-meson-decay analyses are concluded at the end of this thesis.\\
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Date Issued: 2016
Identifier: FSU_FA2016_Zeoli_fsu_0071E_13456
Format: Thesis

Title: Measurement of Polarization Observables in Vector Meson Photoproduction Using a Transversely-Polarized Frozen-Spin Target and Polarized Photons at CLAS, Jefferson Lab.
Creator: Roy, Priyashree, Crede, Volker, Plewa, Tomasz, Capstick, Simon, Eugenio, Paul Michael, Prosper, Harrison B., Florida State University, College of Arts and Sciences, Department...
Show moreRoy, Priyashree, Crede, Volker, Plewa, Tomasz, Capstick, Simon, Eugenio, Paul Michael, Prosper, Harrison B., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: The study of baryon resonances provides a deeper understanding of the strong interaction because the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c² are generally predicted to have strong couplings to final states involving a heavier meson, e. g. one of the vector mesons, ρ, ω, φ, as compared to a lighter pseudoscalar meson, e.g. π and η. Decays to the ππN final...
Show moreThe study of baryon resonances provides a deeper understanding of the strong interaction because the dynamics and relevant degrees of freedom hidden within them are reflected by the properties of the excited states of baryons. Higher-lying excited states at and above 1.7 GeV/c² are generally predicted to have strong couplings to final states involving a heavier meson, e. g. one of the vector mesons, ρ, ω, φ, as compared to a lighter pseudoscalar meson, e.g. π and η. Decays to the ππN final states via π∆ also become more important through the population of intermediate resonances. We observe that nature invests in mass rather than momentum. The excited states of the nucleon are usually found as broadly overlapping resonances which may decay into a multitude of final states involving mesons and baryons. Polarization observables make it possible to isolate single-resonance contributions from other interference terms. The CLAS g9 (FROST) experiment, as part of the N∗ spectroscopy program at Jefferson Laboratory, accumulated photoproduction data using circularly- and linearly-polarized photons incident on a transversely-polarized butanol target (g9b experiment) in the photon energy range 0.3 − 2.4 GeV & 0.7 − 2.1 GeV, respectively. In this work, the analysis of reactions and polarization observables which involve two charged pions, either in the fully exclusive reaction γp → pπ⁺π⁻ or in the semi-exclusive reaction with a missing neutral pion, γp → pπ⁺π⁻ (π⁰) will be presented. For the reaction γp → pπ⁺π⁻ , eight polarization observables (I[superscript s], I[superscript c], P[subscript x], P[subscript y], P[superscript s][subscript x,y], P[superscript c][subscript x,y]) have been extracted. The high statistics data rendered it possible to extract these observables in three dimensions. All of them are first-time measurements. The fairly good agreement of I[superscript s] and I[superscript c] obtained from this analysis with the experimental results from a previous CLAS experiment provides support for the first time measurements. For the reaction γp → pω → pπ⁺ π⁻ (π⁰), five polarization observables (T , Σ, F , H, P ) have been extracted, four of which are first-time measurements at all energies. This analysis thus represents a comprehensive program on vector-meson photoproduction: The ω is observed and studied directly from the data and the polarization observables for the (broad) ρ can be extracted from the double-pion reaction in a partial-wave analysis. The 13 polarization observables extracted in this analysis substantially augment the world database of polarization observables for these reactions and are expected to play a crucial role in identifying the contributing baryon resonances.
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Date Issued: 2016
Identifier: FSU_FA2016_Roy_fsu_0071E_13542
Format: Thesis

Title: A Study of 3Π Production in ΓP → NΠ+Π+Π− and ΓP → Δ++Π+Π−Π− with CLAS at Jefferson Lab.
Creator: Tsaris, Aristeidis, Eugenio, Paul Michael, Plewa, Tomasz, Crede, Volker, Capstick, Simon, Owens, Joseph F., Florida State University, College of Arts and Sciences, Department of...
Show moreTsaris, Aristeidis, Eugenio, Paul Michael, Plewa, Tomasz, Crede, Volker, Capstick, Simon, Owens, Joseph F., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: Apart from the mesons that the constituent quark model predicts, QCD allows for additional states beyond the quark-antiquark system. Previous experiments have performed partial wave analysis on pion-production data and claim observation of an exotic JPC = 1−+ state decaying via ρπ. The g12 experiment took place at Jefferson Lab using the CLAS spectrometer, a liquid hydrogen target was used and a tagged photon beam. By studying the reactions γp → nπ+π +π − and γp → ∆++π +π −π −, the...
Show moreApart from the mesons that the constituent quark model predicts, QCD allows for additional states beyond the quark-antiquark system. Previous experiments have performed partial wave analysis on pion-production data and claim observation of an exotic JPC = 1−+ state decaying via ρπ. The g12 experiment took place at Jefferson Lab using the CLAS spectrometer, a liquid hydrogen target was used and a tagged photon beam. By studying the reactions γp → nπ+π +π − and γp → ∆++π +π −π −, the photoproduction of mesons decaying to 3π was studied using two different but complimentary channels. Events are selected with low four-momentum transfer to the baryon, in order to enhance one pion exchange production. For both 3π systems the data exhibit two intermediate decays, ρπ and f2π. For the γp → nπ+π +π − reaction over 600k events were acquired resulting in the largest 3π photoproduction dataset to date. The exotic JPC= 1−+ partial wave does not show resonant behavior and more so it is strongly consistent with a non-resonant non-interfering wave relative to a resonant π2(1670). Furthermore, the partial wave analysis shows production of the a2(1320) and π2(1670) mesons. For the first time we report observation of a photoproduced a1(1260) meson. For the γp → ∆++π +π −π − reaction nearly 350k events were analyzed. A partial wave analysis was performed for the first time on this channel. The a1(1260), a2(1320), and the π2(1670) mesons were observed. Observation of the a1(1260) confirms the result first reported in γp → nπ+π +π − reaction.
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Date Issued: 2016
Identifier: FSU_2016SP_Tsaris_fsu_0071E_13044
Format: Thesis

Title: Magnetic Phase Diagram of Triangular Lattice Antiferromagnet Ba₃MNb₂O9 (M = Co, Mn) and Its Multiferroicity.
Creator: Lee, Minseong, Choi, Eun Sang, Manousakis, Efstratios, Dalal, Naresh S., Chiorescu, Irinel, Crede, Volker, Florida State University, College of Arts and Sciences, Department of...
Show moreLee, Minseong, Choi, Eun Sang, Manousakis, Efstratios, Dalal, Naresh S., Chiorescu, Irinel, Crede, Volker, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: This dissertation mainly focuses on the investigation of the magnetic phase diagram of quasi two di- mensional triangular lattice antiferromagnets (TLAFs) Ba₃MNb₂O9 (M = Co2+ (S = 1/2), Mn2+ (S = 5/2)), and their multiferroic properties. Both compounds show a two-step magnetic phase transition at TN1 and TN2 upon cooling from paramagnetic to up-up-down(uud) phase due to the easy-axis anisotropy, and 120 degree ordered phase at zero field. This feature is dissimilar to that of sister a...
Show moreThis dissertation mainly focuses on the investigation of the magnetic phase diagram of quasi two di- mensional triangular lattice antiferromagnets (TLAFs) Ba₃MNb₂O9 (M = Co2+ (S = 1/2), Mn2+ (S = 5/2)), and their multiferroic properties. Both compounds show a two-step magnetic phase transition at TN1 and TN2 upon cooling from paramagnetic to up-up-down(uud) phase due to the easy-axis anisotropy, and 120 degree ordered phase at zero field. This feature is dissimilar to that of sister a compound Ba₃MNb₂O9 (Ni2+, (S = 1)), in which a single magnetic phase transition occurs due to the easy-plane anisotropy at zero field. Moreover, at low temperature below TN1, successive magnetic phase transitions were observed in both compounds. However, in case of Co compounds, the range of magnetic field where the uud phase stabilizes becomes wider at lower temperature whereas becomes narrower in case of Mn compounds. This different behavior is originated from the nature of the fluctuations that stabilize the uud phase, that is, quantum and/or classical fluctuations. We also found that the spin magnitude and spin structure play a crucial role in stabilizing the multiferroic ground state. Multiferroicity appears in all magnetically ordered phase in the small-spin-system Co compound but only in 120 degree ordered state in the large-spin-system Mn compound. The systematic studies on these compounds provide a highly valuable playground in the investigate of the effect of spin varied from 1/2 to 5/2 in frustrated magnets and multiferroics, attract many interests and in the field.
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Date Issued: 2016
Identifier: FSU_2016SP_Lee_fsu_0071E_13120
Format: Thesis

Title: J/Ψ Yield Modification in 200 GeV Per Nucleon Au+Au Collisions with the PHENIX Experiment at RHIC.
Creator: Klatsky, Jeffrey, Frawley, Anthony D., Crede, Volker, Cross, Timothy A., Blessing, Susan K., Capstick, Simon, Florida State University, College of Arts and Sciences, Department...
Show moreKlatsky, Jeffrey, Frawley, Anthony D., Crede, Volker, Cross, Timothy A., Blessing, Susan K., Capstick, Simon, Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: It has been believed for over 30 years that matter will become a deconfined state of quarks and gluons at sufficiently high energy densities. As the energy density increases, deconfinement occurs due to Debye screening of the color charges, which disrupts the binding of mesons and baryons. The expected deconfinement transition to quark-gluon plasma (QGP) has been observed using collisions of heavy ions to create high energy densities, first at the Relativistic Heavy Ion Collider (RHIC) at...
Show moreIt has been believed for over 30 years that matter will become a deconfined state of quarks and gluons at sufficiently high energy densities. As the energy density increases, deconfinement occurs due to Debye screening of the color charges, which disrupts the binding of mesons and baryons. The expected deconfinement transition to quark-gluon plasma (QGP) has been observed using collisions of heavy ions to create high energy densities, first at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, and more recently at the Large Hadron Collider (LHC) at European Organization for Nuclear Research (CERN). The degree to which the binding of a hadron in the plasma is disrupted depends on its radius. Because deconfinement is caused by Debye screening, and the screening length is determined by energy density, small tightly bound heavy quark mesons (referred to as quarkonia) may become deconfined at a higher energy density than the light quark hadrons. Thus, measuring quarkonia production may provide a way to determine the screening length in the QGP, and a program of measurements of modification of charmonium and bottomonium states in heavy ion collisions has been carried out at several accelerators over the last two decades. As part of this effort, measurements of J/psi production in Au+Au collisions have been made by the PHENIX experiment at RHIC, the subject of this thesis. Specifically, J/psi --> e+e- data from Sqrt(sNN) = 200 GeV Au+Au collisions were recorded in 2004, providing the first major quarkonia result from PHENIX. A higher statistics measurement was performed in 2007, but a non-functioning detector subsystem in the PHENIX central arms rendered the data unusable. A still larger data set was recorded 2010, this time with the previously non-functioning detector system working. It is these 2010 data that are the focus of the present analysis. The 2010 dataset contains about 5 times as many measured J/psi as the 2004 dataset. However the increase in signal is accompanied by a large increase in background electrons, which introduces difficulties not present in the 2004 analysis. The goal of this analysis was to improve on the result from the 2004 measurement.
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Date Issued: 2016
Identifier: FSU_2016SP_Klatsky_fsu_0071E_13162
Format: Thesis

Title: ΛC Semileptonic Decays in a Quark Model.
Creator: Hussain, Md Mozammel, Roberts, Winston, Goldsby, Kenneth A,, Volya, Alexander, Crede, Volker, Owens, Joseph F., Florida State University, College of Arts and Sciences,...
Show moreHussain, Md Mozammel, Roberts, Winston, Goldsby, Kenneth A,, Volya, Alexander, Crede, Volker, Owens, Joseph F., Florida State University, College of Arts and Sciences, Department of Physics
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Abstract/Description: Hadronic form factors for semileptonic decay of the Λ[subscript c] are calculated in a nonrelativistic quark model. The full quark model wave functions are employed to numerically calculate the form factors to all orders in (1/m[subscript c], 1/m[subscript s]). The form factors satisfy relationships expected from the heavy quark effective theory (HQET) form factors. No other semileptonic decays of Λ[subscript c] has been reported other than the decay to the ground state Λ that implies f = B(Λ...
Show moreHadronic form factors for semileptonic decay of the Λ[subscript c] are calculated in a nonrelativistic quark model. The full quark model wave functions are employed to numerically calculate the form factors to all orders in (1/m[subscript c], 1/m[subscript s]). The form factors satisfy relationships expected from the heavy quark effective theory (HQET) form factors. No other semileptonic decays of Λ[subscript c] has been reported other than the decay to the ground state Λ that implies f = B(Λ[subscript c]⁺ → Λl⁺ν[subscript l])/B(Λ[subscript c]⁺ → X[subscript s]l⁺ν[subscript l]) = 1. In this work, the differential decay rates and branching fractions are calculated for transitions to the ground state and a number of excited states of Λ. The branching fraction of the semileptonic decay width to the total width of Λ[subscript c] has been calculated and compared with other theoretical estimates and experimental results. The branching fractions for Λ[subscript c] → Λ*l⁺ν[subscript l] → Σπl⁺ν[subscript l] and Λ[subscript c] → Λ*l⁺ν[subscript l] → NǨl⁺ν[subscript l] are also calculated. Apart from decays to the ground state Λ(1115), it is found that decays through the Λ(1405) provide a significant portion of the branching fraction Λ[subscript c] → X[subscript s]lν[subscript l]. There are various conjectures on the structure of the Λ(1405) while we treated it as a three quark state. A new estimate for f = B(Λ[subscript c]⁺ → Λl⁺ν[subscript l] is obtained.
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Date Issued: 2017
Identifier: FSU_2017SP_Hussain_fsu_0071E_13920
Format: Thesis

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