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SANE's Measurement of the Proton's Virtual Photon Spin Asymmetry, A^p_1, at Large Bjorken x (open access)

SANE's Measurement of the Proton's Virtual Photon Spin Asymmetry, A^p_1, at Large Bjorken x

The experiment SANE (Spin Asymmetries of the Nucleon Experiment) measured inclusive double polarization electron asymmetries on a proton target at the Continuous Electron Beam Accelerator Facility at the Thomas Jefferson National Laboratory in Newport News Virgina. Polarized electrons were scattered from a solid {sup 14}NH{sub 3} polarized target provided by the University of Virginia target group. Measurements were taken with the target polarization oriented at 80 degrees and 180 degrees relative to the beam direction, and beam energies of 4.7 and 5.9 GeV were used. Scattered electrons were detected by a multi-component novel non-magnetic detector package constructed for this experiment. Asymmetries measured at the two target orientations allow for the extraction of the virtual Compton asymmetries A{sub 1}{sup p} and A{sub 2}{sup p} as well as the spin structure functions g{sub 1}{sup p} and g{sub 2}{sup p}. This work addresses the extraction of the virtual Compton asymmetry A{sub 1}{sup p} in the deep inelastic regime. The analysis uses data in the kinematic range from Bjorken x of 0.30 to 0.55, separated into four Q{sup 2} bins from 1.9 to 4.7 GeV{sup 2}.
Date: May 1, 2012
Creator: Mulholland, Jonathan
System: The UNT Digital Library
Polarized {sup 3}He(e,e'n) Asymmetries in Three Orthogonal Measurements (open access)

Polarized {sup 3}He(e,e'n) Asymmetries in Three Orthogonal Measurements

Asymmetry measurements were conducted in Jefferson Lab's experimental Hall A through electron scattering from a polarized {sup 3}He target in the quasi-elastic polarized-{sup 3}He(e,e'n) reaction. Measurements were made with the target polarized in the longitudinal direction with respect to the incoming electrons A_L, in a transverse direction that was orthogonal to the beam-line and parallel to the q-vector A_T, and in a vertical direction that was orthogonal to both the beam-line and the q-vector (A_y^0). The experiment measured $A_y^0$ at four-momentum transfer squared Q^2 of 0.127 (GeV/c)^2, 0.456 (GeV/c)^2, and 0.953 (GeV/c)^2. The A_T and A_L asymmetries were both measured at Q^2 of 0.505 (GeV/c)^2 and 0.953 (GeV/c)^2. This is the first time that three orthogonal asymmetries have been measured simultaneously. Results from this experiment are compared with the plane wave impulse approximation (PWIA) and Faddeev calculations. These results provide important tests of models that use 3He as an effective neutron target and show that the PWIA holds above Q^2 of 0.953 (GeV/c)^2.
Date: September 1, 2012
Creator: Long, Elena
System: The UNT Digital Library
Measurement of double polarized asymmetries in quasi-elastic processes ${}^3\vec{He}(\vec{e},e' d)$ and ${}^3\vec{He}(\vec{e},e' p)$ (open access)

Measurement of double polarized asymmetries in quasi-elastic processes ${}^3\vec{He}(\vec{e},e' d)$ and ${}^3\vec{He}(\vec{e},e' p)$

This thesis is dedicated to a study of a spin-isospin structure of the polarized {sup 3}He. First, an introduction to the spin structure of {sup 3}He is given, followed by a brief overview of past experiments. The main focus of the thesis is the E05-102 experiment at Jefferson Lab, in which the reactions {sup 3}{ovr He} ({rvec e}, e'd) and {sup 3}{ovr He} ({rvec e}, e'p) in the quasi-elastic region were studied. The purpose of this experiment was to better understand the effects of the S'- and D-state contributions to the {sup 3}He ground-state wave-functions by a precise measurement of beam-target asymmetries A{sub x} and A{sub z} in the range of recoil momenta from 0 to about 300 MeV/c. The experimental equipment utilized in these measurements is described, with special attention devoted to the calibration of the hadron spectrometer, BigBite. Results on the measured asymmetries are presented, together with first attempts at their comparison to the state-of-the art Faddeev calculations. The remaining open problems and challenges for future work are also discussed.
Date: August 1, 2012
Creator: Mihovilovic, Miha
System: The UNT Digital Library
Enhanced performance of organic light-emitting diodes (OLEDs) and OLED-based photoluminescent sensing platforms by novel microstructures and device architectures (open access)

Enhanced performance of organic light-emitting diodes (OLEDs) and OLED-based photoluminescent sensing platforms by novel microstructures and device architectures

After a general introduction to OLEDs and OLED-based PL sensors, the transient emission mechanism of guest-host OLEDs is described both experimentally and theoretically. A monolithic and easy-to-apply process is demonstrated for fabricating multicolor microcavity OLEDs (that improve the sensor platform). The outcoupling issues of OLEDs at the substrate/air interface are addressed by using a microstructured polymer film resulting from a PS and polyethylene glycol (PEG) mixture. Based on the understanding of OLEDs and their improvement, research was done in order to realize integrated all organic-based O{sub 2} and pH sensors with improved signal intensity and sensitivity. The sensor design modification and optimization are summarized
Date: August 1, 2012
Creator: Liu, Rui
System: The UNT Digital Library
Application of Chebyshev Formalism to Identify Nonlinear Magnetic Field Components in Beam Transport Systems (open access)

Application of Chebyshev Formalism to Identify Nonlinear Magnetic Field Components in Beam Transport Systems

An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a beam-based technique for characterizing the extent of the nonlinearity of the magnetic fields of a beam transport system. Horizontally and vertically oriented pairs of air-core kicker magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the beam orbit relative to the unperturbed reference orbit. Fourier decomposition of the position data at eight different points along the beamline was then used to measure the amplitude of these frequencies. For a purely linear transport system one expects to find solely the frequencies that were applied to the kickers with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. Chebyshev polynomials and their unique properties allow one to directly quantify the magnitude of the nonlinearity with the minimum error. A calibration standard was developed using one of the sextupole magnets in a CEBAF beamline. The technique was then applied to a pair of Arc 1 dipoles and then to the magnets in the Transport Recombiner beamline to …
Date: August 1, 2012
Creator: Spata, Michael
System: The UNT Digital Library
Study of Generalized Parton Distributions and Deeply Virtual Compton Scattering on the nucleon with the CLAS and CLAS12 detectors at the Jefferson Laboratory (open access)

Study of Generalized Parton Distributions and Deeply Virtual Compton Scattering on the nucleon with the CLAS and CLAS12 detectors at the Jefferson Laboratory

The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.
Date: November 1, 2012
Creator: Guegan, Baptiste
System: The UNT Digital Library
Study of the Two-pion Photoproduction on the Deuteron (open access)

Study of the Two-pion Photoproduction on the Deuteron

Understanding the structure of baryons in terms of the fundamental interaction of the constituent quarks and gluons is one of the primary challenges in strong interaction physics. This interaction is governed by Quantum Chromodynamics (QCD), which is a theory for understanding the dynamics of strong. QCD displays the asymptotic freedom of hadrons at very short distances and also the confinement of quarks and gluons inside hadrons. However, solutions of this QCD theory in the non-perturbative domain of the interaction are extremely difficult to achieve, mainly because confinement happens on the hadronic scale on which the coupling constant is large and prevents any perturbative approach. Thus leaving us with strategies such as lattice QCD or formulating QCD sum rules to get around this problem. In exclusive hadron production the yN interaction is recognized for being a powerful method for investigating hadrons and the mysteries that still exist within the strong interaction. From reactions with the nucleon, the strong interaction can be investigated through the transition amplitudes to the N and Delta resonances. More specifically, if an electromagnetic interaction is well known then the intermediate resonance states may be evaluated through meson photoproduction. To gain more detailed insight into this interaction, we …
Date: December 1, 2012
Creator: Graham, Lewis P.
System: The UNT Digital Library
Precision Measurement of Electroproduction of pi{sup 0} near Threshold (open access)

Precision Measurement of Electroproduction of pi{sup 0} near Threshold

Electromagnetic production of neutral pions near threshold is the most basic, lowest energy reaction in which a new hadron is created. The electromagnetic interaction is well understood so measurements of this reaction can yield direct insight into the hadronic production mechanism. During the past three decades there have been many developments in both the measurement and theory of threshold pion production, starting with measurements of photo-production at Saclay in 1986 and at Mainz in 1990. These measurements indicated a surprising discrepancy with so-called Low Energy Theorems (LETs) which are based on quite fundamental symmetries and considerations. Chiral Perturbation Theory (ChPT) is an e#11;ective #12;eld theoretic description of the nuclear force which contains the underlying symmetries of the force but deals with nucleons and pions rather than quarks and gluons. It has the advantage of being applicable at low energies but requires tuning some parameters to experimental data. Once these parameters have been determined ChPT predicts how the reaction should behave as a function of the kinematic variable. When applied to the reaction, p({gamma},{pi}{sup 0})p, near threshold it explained the discrepancy with the LETs and made predictions for electroproduction, p(e,e'p){pi}#25;{sup 0}. Electroproduction measurements at Mainz in the 1990's showed a clear …
Date: May 1, 2012
Creator: Chirapatpimol, Khem
System: The UNT Digital Library