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- Creators: Ravel, Maurice, 1875-1937
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 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
Description
Preliminary feasibility studies for two possible experiments with the GlueX detector, installed in Hall D of Jefferson Laboratory, are presented. First, a general study of the feasibility of detecting the ηC at the current hadronic rate is discussed, without regard for detector or reconstruction efficiency. Second, a study of the use of statistical methods in studying exotic meson candidates is outlined, describing methods and providing preliminary data on their efficacy.
ContributorsPrather, Benjamin Scott (Author) / Ritchie, Barry G. (Thesis director) / Dugger, Michael (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Physics (Contributor)
Created2015-05
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 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
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 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.
(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
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 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.
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
Description
In the quark model, meson states consisting of a quark/anti-quark pair must obey Poincaré symmetry. As a result of that symmetry, for meson total angular momentum J, parity P, and charge conjugation symmetry C, states with JPC= 0--, 0+-, 1-+, 2+-, 3-+, 4+-, … should not be observed. A meson observed experimentally with such quantum numbers would indicate a so-called “exotic” meson state. Exotic mesons can be multi-quark states like tetraquarks, a combination of two or more gluons known as glueballs, or a hybrid meson (qqg). Theories have suggested that three possible exotic meson states with the 1-+ quantum number: π1, η1, and η‘1,. However, no conclusive evidence for the existence of these three exotic states has been observed. This research will look for new states that decay to K* K final states with an emphasis on exotic mesons. An analysis of K+ K- π0 final states will be presented, where a restriction on the K - π0 invariant mass yields an unexpected enhancement in the K+ K- π0 spectrum.
ContributorsWalker, Patrick J (Author) / Dugger, Michael (Thesis director) / Sukharev, Maxim (Committee member) / College of Integrative Sciences and Arts (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
ContributorsRavel, Maurice, 1875-1937 (Composer) / Goulart, Renato (Arranger)
ContributorsRavel, Maurice, 1875-1937 (Composer)
ContributorsRavel, Maurice, 1875-1937 (Composer)
ContributorsRavel, Maurice, 1875-1937 (Composer) / Schoenbach, Sol (Arranger)