Matching Items (12)
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Description
The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been

The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results presented here were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 MeV to 2.35 GeV. Data are presented for the E polarization observable for eta meson photoproduction on the proton from threshold (W=1500 MeV) to W=1900 MeV. Comparisons to the partial wave analyses of SAID and Bonn-Gatchina along with the isobar analysis of eta-MAID are made. These results will help distinguish between current theoretical predictions and refine future theories.
ContributorsMorrison, Brian (Author) / Ritchie, Barry (Thesis advisor) / Dugger, Michael (Committee member) / Shovkovy, Igor (Committee member) / Davies, Paul (Committee member) / Alarcon, Ricardo (Committee member) / Arizona State University (Publisher)
Created2011
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Description
In this thesis a new method based on the Tight-Binding Linear Muffin Tin Orbital (TB-LMTO) formalism and the Quasiparticle Self-consistent GW (QSGW) approximation is proposed. The method is capable of generating accurate electronic bands structure of large supercells necessary to model alloys structures. The strategy consist in building simple and

In this thesis a new method based on the Tight-Binding Linear Muffin Tin Orbital (TB-LMTO) formalism and the Quasiparticle Self-consistent GW (QSGW) approximation is proposed. The method is capable of generating accurate electronic bands structure of large supercells necessary to model alloys structures. The strategy consist in building simple and small hamiltonian from linear Muffin-tin-orbitals (LMTO). Parameters in this hamiltonian are then used to fit the difference in QSGW self-energies and LDA exchange-correlation potentials. The parameter are assumed to transfer to new environments --- a procedure we check carefully by comparing our predicted band to QSGW bands for small supercells. The method possess both the accuracy of the QSGW approximation, (which is the most reliable way to determine energy bands accurately, and yet too expensive for the large supercells required here), and the efficiency of the TB-LMTO method. The accurate and highly efficient hamiltonian is used to predict the electronic and optical transitions of Si1-xGex alloys and SnxSiyGe1-x-y alloys. The goal is to engineer direct band gap material compatible with the silicon technology. The results obtained are compared to available experimental data.
ContributorsDonfack, Hermann Azemtsa (Author) / Van Schilfgaarde, Mark (Thesis advisor) / Dow, John D. (Thesis advisor) / Ponce, Fernando (Committee member) / Ritchie, Barry (Committee member) / Chamberlin, Ralph (Committee member) / Arizona State University (Publisher)
Created2011
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Description
A search is underway to find baryon resonances that have been predicted, but yet remain unobserved. Nucleon resonances, due to their broad energy widths, overlap and must be disentangled in order to be identified. Meson photoproduction observables related to the orientation of the spin of the incoming photon and the

A search is underway to find baryon resonances that have been predicted, but yet remain unobserved. Nucleon resonances, due to their broad energy widths, overlap and must be disentangled in order to be identified. Meson photoproduction observables related to the orientation of the spin of the incoming photon and the spin of the target proton are useful tools to deconvolve the nucleon resonance spectrum. These observables are particularly sensitive to interference between phases of the complex amplitudes. A set of these observables has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab with linearly-polarized photons having energies from 725 to 1575 MeV with polar angle values of cos(theta) between -0.8 and 0.9 and transversely-polarized protons in the Jefferson Lab FRozen Spin Target (FROST). By fitting neutron yields from gamma p -> pi^+ n over azimuthal scattering angle, the observables \H and P have been extracted. These observables manifest as azimuthal modulations in the yields for the double-polarization experiment. Preliminary results for these observables will be presented and compared with predictions provided by the SAID Partial-Wave Analysis Facility.
ContributorsLee, Robert John (Author) / Dugger, Michael (Thesis director) / Ritchie, Barry (Committee member) / Department of Physics (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
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Description
A series of experiments using a polarized beam incident on a polarized frozen spin target

(FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken

during the second running period with the FROST target using the CEBAF Large Acceptance

Spectrometer (CLAS) detector at Jefferson Lab, which used transversely-polarized

protons in a

A series of experiments using a polarized beam incident on a polarized frozen spin target

(FROST) was conducted at Jefferson Lab in 2010. Results presented here were taken

during the second running period with the FROST target using the CEBAF Large Acceptance

Spectrometer (CLAS) detector at Jefferson Lab, which used transversely-polarized

protons in a butanol target and a circularly-polarized incident tagged photon beam with

energies between 0.62 and 2.93 GeV. Data are presented for the F and T polarization observables

for h meson photoproduction on the proton from W = 1.55 GeV to 1.80 GeV.

The data presented here will improve the world database and refine theoretical approaches

of nucleon structure.
ContributorsTucker, Ross (Author) / Ritchie, Barry (Thesis advisor) / Dugger, Michael (Committee member) / Alarcon, Ricardo (Committee member) / Lebed, Richard (Committee member) / Arizona State University (Publisher)
Created2016
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Description
The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). The motivation for the experiment stemmed from measurements of the electric-to-magnetic form factor ratio of the proton \(\mu G_E/G_M\) extracted from polarization observables in

The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). The motivation for the experiment stemmed from measurements of the electric-to-magnetic form factor ratio of the proton \(\mu G_E/G_M\) extracted from polarization observables in polarized electron-proton scattering. Polarized electron-proton scattering experiments have revealed a significant decrease in \(\mu G_E/G_M\) at large \(Q^2\), in contrast to previous measurements from unpolarized electron-proton scattering. The commonly accepted hypothesis is that the discrepancy in the form factor ratio is due to neglected higher-order terms in the elastic electron-proton scattering cross section, in particular the two-photon exchange amplitude.

The goal of OLYMPUS was to measure the two-photon exchange contribution by measuring the positron-proton to electron-proton elastic scattering cross section ratio, \(\sigma_{e^+p}/\sigma_{e^-p}\). The two-photon exchange contribution is correlated to the deviation of the cross section ratio from unity.

In 2012, the OLYMPUS experiment collected over 4 fb\(^{-1}\) of \(e^+p\) and \(e^-p\) scattering data using electron and positron beams incident on a hydrogen gas target. The scattered leptons and protons were measured exclusively with a large acceptance spectrometer. OLYMPUS observed a slight rise in \(\sigma_{e^+p}/\sigma_{e^-p}\) of at most 1-2\% over a \(Q^2\) range of \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). This work discusses the motivations, experiment, analysis method, and the preliminary results for the cross section ratio as measured by OLYMPUS.
ContributorsIce, Lauren (Author) / Alarcon, Ricardo O (Thesis advisor) / Dugger, Michael (Committee member) / Lebed, Richard (Committee member) / Ritchie, Barry (Committee member) / Arizona State University (Publisher)
Created2016
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Description
The spectra of predicted particles from elementary quark models (CQMs) are expansive, accurate for the low-lying spectra, but incomplete. The GlueX experiment at Jefferson Lab is a vehicle to study medium energy photoproduction of hadronic states. The primary goal of the GlueX collaboration is to study Quantum Chromodynamics (QCD, also

The spectra of predicted particles from elementary quark models (CQMs) are expansive, accurate for the low-lying spectra, but incomplete. The GlueX experiment at Jefferson Lab is a vehicle to study medium energy photoproduction of hadronic states. The primary goal of the GlueX collaboration is to study Quantum Chromodynamics (QCD, also known as the strong nuclear force) and the nature of quark confinement. The GlueX collaboration uses a polarized photon beam incident on a liquid hydrogen target (LH2) to investigate the aftermath of photon-proton interactions.The cascade baryons, denoted by Ξ, are defined by having two, second-generation, strange quarks with an additional first-generation light quark (u or d). Experimentally, few cascades have been discovered, which is the antithesis of what most models expect. The cascades have some favorable attributes but are difficult to detect because the production cross sections are small and direct production is unlikely. Fortunately, in the 12 GeV era of the GlueX experiment, there is sufficient energy, beam time and data analysis tools for the detection of excited cascade states and their properties. From the reaction γp→K^+ K^+ Ξ^- π^0, the invariant mass spectra of Ξ^- π^0 system was surveyed for new possible resonances. The invariant mass spectrum has a strong Ξ(1530) signal with other smaller resonances throughout the spectrum. Preliminary cross sections for the Ξ(1530) that was photoproduced from the proton are presented at energies never before explored. While the Ξ(1530) couples almost exclusively to the Ξπ channel, there is an easily identifiable Ξ(1690) signal decaying Ξπ. Through the use of a simultaneous fitting routing of the Ξ*- mass spectra, I was able to observe the Ξ(1690) decaying to the KΛ, as well as to the Ξ-π0 branch. With additional statistics, a measurement of the branching ratio should be possible. Lastly, a partial wave analysis (PWA) was completed to verify that the total angular momentum of Ξ(1530) is J = 3/2 and consistent with having positive parity. Additionally, there is evidence of a potentially interesting feature slightly above the mass of the Ξ(1530) that should be more fully explored as new GlueX data becomes available.
ContributorsSumner, Brandon Christopher Lamont (Author) / Dugger, Michael (Thesis advisor) / Ritchie, Barry (Committee member) / Lebed, Richard (Committee member) / Alarcon, Ricardo (Committee member) / Arizona State University (Publisher)
Created2022
Description

In nuclear physics, there is a discrepancy between theory and experiment concerning the number of existing nucleon resonances. Current models predict far more states than have been observed. In particular, few searches have found excited nucleon resonances with energies above 2.2 GeV in the K Lambda channel. To investigate high-mass

In nuclear physics, there is a discrepancy between theory and experiment concerning the number of existing nucleon resonances. Current models predict far more states than have been observed. In particular, few searches have found excited nucleon resonances with energies above 2.2 GeV in the K Lambda channel. To investigate high-mass nucleon resonances, efficiency-corrected yields of the reaction ep --> e K+ Lambda(1520) --> e K+ K- p in the center-of-mass energy range 2.1-4.5 GeV are constructed utilizing Jefferson Lab's CLAS12 detector. This paper presents the results of an analysis searching for high-mass nucleon resonances in the K Lambda channel between 2.1-4.5 GeV.

ContributorsOsar, Rebecca (Author) / Dugger, Michael (Thesis director) / Ritchie, Barry (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / School of International Letters and Cultures (Contributor)
Created2023-05
Description

Exclusive neutral-pion electroproduction (ep → e'p'π0) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections d4σ/dtdQ2dxBπ and structure functions σT + εσL, σTT, and σLT as functions of t were obtained over a wide range of Q2 and xB. The data are

Exclusive neutral-pion electroproduction (ep → e'p'π0) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections d4σ/dtdQ2dxBπ and structure functions σT + εσL, σTT, and σLT as functions of t were obtained over a wide range of Q2 and xB. The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found that the inclusion of vector meson rescattering processes is necessary to bring the magnitude of the calculated and measured structure functions into rough agreement. In the handbag framework, there are two independent calculations, both of which appear to roughly explain the magnitude of the structure functions in terms of transversity generalized parton distributions.

ContributorsBedlinskiy, I. (Author) / Kubarovsky, V. (Author) / Niccolai, S. (Author) / Stoler, P. (Author) / Adhikari, K. P. (Author) / Anderson, M. D. (Author) / Pereira, S. Anefalos (Author) / Avakian, H. (Author) / Ball, J. (Author) / Baltzell, N. A. (Author) / Battaglieri, M. (Author) / Batourine, V. (Author) / Biselli, A. S. (Author) / Boiarinov, S. (Author) / Bono, J. (Author) / Briscoe, W. J. (Author) / Brooks, W. K. (Author) / Burkert, V. D. (Author) / Carman, D. S. (Author) / Celentano, A. (Author) / Chandavar, S. (Author) / Colaneri, L. (Author) / Cole, P. L. (Author) / Contalbrigo, M. (Author) / Cortes, O. (Author) / Crede, V. (Author) / D'Angelo, A. (Author) / Dashyan, N. (Author) / De Vita, R. (Author) / De Sanctis, E. (Author) / Deur, A. (Author) / Djalali, C. (Author) / Doughty, D. (Author) / Dupre, R. (Author) / Egiyan, H. (Author) / Ritchie, Barry (Author) / Senderovich, Igor (Author) / College of Liberal Arts and Sciences (Contributor)
Created2014-08-13
Description

High-statistics measurements of differential cross sections and spin density matrix elements for the reaction γp → ϕp have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.97 to 2.84 GeV, with an extensive coverage in the ϕ production angle. The high statistics of

High-statistics measurements of differential cross sections and spin density matrix elements for the reaction γp → ϕp have been made using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.97 to 2.84 GeV, with an extensive coverage in the ϕ production angle. The high statistics of the data sample made it necessary to carefully account for the interplay between the ϕ natural lineshape and effects of the detector resolution, that are found to be comparable in magnitude. We study both the charged- (ϕ → K+K-) and neutral- (ϕ → K[0 over S]K[0 over L]) K[⎯⎯⎯ over K] decay modes of the ϕ. Further, for the charged mode, we differentiate between the cases where the final K- track is directly detected or its momentum reconstructed as the total missing momentum in the event. The two charged-mode topologies and the neutral-mode have different resolutions and are calibrated against each other. Extensive usage is made of kinematic fitting to improve the reconstructed ϕ mass resolution. Our final results are reported in 10- and mostly 30-MeV-wide √s bins for the charged- and the neutral-modes, respectively. Possible effects from K+Λ* channels with pK[⎯⎯⎯ over K] final states are discussed. These present results constitute the most precise and extensive ϕ photoproduction measurements to date and in conjunction with the ω photoproduction results recently published by CLAS, will greatly improve our understanding of low energy vector meson photoproduction.

ContributorsDey, B. (Author) / Meyer, C. A. (Author) / Bellis, M. (Author) / Williams, M. (Author) / Adhikari, K. P. (Author) / Adikaram, D. (Author) / Aghasyan, M. (Author) / Amaryan, M. J. (Author) / Anderson, M. D. (Author) / Pereira, S. Anefalos (Author) / Ball, J. (Author) / Baltzell, N. A. (Author) / Battaglieri, M. (Author) / Bedlinskiy, I. (Author) / Biselli, A. S. (Author) / Bono, J. (Author) / Boiarinov, S. (Author) / Briscoe, W. J. (Author) / Brooks, W. K. (Author) / Burkert, V. D. (Author) / Carman, D. S. (Author) / Celentano, A. (Author) / Chandavar, S. (Author) / Colaneri, L. (Author) / Cole, P. L. (Author) / Contalbrigo, M. (Author) / Cortes, O. (Author) / Crede, V. (Author) / D'Angelo, A. (Author) / Dashyan, N. (Author) / De Vita, R. (Author) / De Sanctis, E. (Author) / Deur, A. (Author) / Djalali, C. (Author) / Doughty, D. (Author) / Dugger, Michael (Author) / Pasyuk, Eugene (Author) / Ritchie, Barry (Author) / Senderovich, Igor (Author) / College of Liberal Arts and Sciences (Contributor)
Created2014-05-27
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Description
The current observable universe is made of matter due to baryon/antibaryon asymmetry. The Deep Underground Neutrino Experiment is an international experiment through the Fermi National Accelerator Laboratory that will study neutrinos. In this study, the detection efficiency for low energy supernova neutrinos was examined in order to improve energy reconstruction

The current observable universe is made of matter due to baryon/antibaryon asymmetry. The Deep Underground Neutrino Experiment is an international experiment through the Fermi National Accelerator Laboratory that will study neutrinos. In this study, the detection efficiency for low energy supernova neutrinos was examined in order to improve energy reconstruction for neutrino energies less than 40 MeV. To do this, supernova neutrino events were simulated using the LarSoft simulation package with and without background. The ratios between the true data and reconstructed data were compared to identify the deficiencies of the detector, which were found to be low energies and high drift times. The ratio between the true and reconstructed data was improved by applying the physical limits of the detector. The efficiency of the improved ratio of the clean data was found to be 93.2% and the efficiency of the improved ratio with the data with background was 82.6%. The study suggests that a second photon detector at the far wall of the detector would help improve the resolutions at high drift times and low neutrino energies.
ContributorsProcter-Murphy, Rachel Grace (Co-author) / Procter-Murphy, Rachel (Co-author) / Ritchie, Barry (Thesis director) / LoSecco, John (Committee member) / School of Earth and Space Exploration (Contributor) / Department of Physics (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05