Physics Commons^™

Dihadron Beam Spin Asymmetries On An Unpolarized Hydrogen Target With Clas12, Timothy Barton Hayward

Dissertations, Theses, and Masters Projects

The semi-inclusive deep inelastic scattering process, where an electron scatters off a proton target at high enough energy that the process can be described by the scattering off a single constituent particle, offers targeted access to the internal structure of the nucleon. The process can be described in two phases by parton distribution functions (PDFs), which describe the likelihood of finding a quark or gluon in a particular state inside of the nucleon and then by fragmentation functions (FFs) which describe the likelihood of forming a particular final state particle. One way to study these properties is via the measurement …

Extraction And Parametrization Of Isobaric Trinucleon Elastic Cross Sections And Form Factors, Scott Kevin Barcus

Dissertations, Theses, and Masters Projects

By mining data from Jefferson Lab Hall A experiment E08-014 a new measurement of the 3He elastic cross section at Q^2 ≈ 34 fm^−2 was extracted from a large quasielastic background. This new data point falls approximately halfway between the first and second diffractive minima of the 3He form factors. When combined with recent high Q^2 3He elastic cross section measurements from JLab this new point improves our knowledge of the cross section and form factors at large momentum transfers. The new high Q^2 data motivate a reanalysis of the 3He elastic cross section world data and promise an improved …

First Measurements Of The Parity-Violating And Beam-Normal Single-Spin Asymmetries In Elastic Electron-Aluminum Scattering, Kurtis David Bartlett

Dissertations, Theses, and Masters Projects

The Qweak collaboration has made the first measurements of the elastic parity-violating and beam-normal single-spin asymmetries from the 27Al nucleus. Both are the result of ancillary measurements conducted during the Qweak experiment at Jefferson Lab. The goal of the experimental was to determine the proton's weak charge, Qp W, via a measurement of the elastic parity-violating electron-proton scattering asymmetry. During the experiment, ancillary measurements were made with different beam configurations on a separate aluminum alloy target, in an effort to directly measure the aluminum background coming from the experiment's liquid hydrogen target cell.

This dissertation discusses three primary results: the …

Measurement Of The Elastic Ep Cross Section At Q2 = 0.66, 1.10, 1.51 And 1.65 Gev2, Yang Wang

Dissertations, Theses, and Masters Projects

The nucleon form factors have been investigated by physicists for decades because of its fundamental importance. The world data of the proton magnetic form factor GMp shows that the measurements have been focused on Q2 lower than 5 GeV2 and it has large uncertainties at higher GeV2. Experiment E12-07-108 aims to improve the accuracy of the e − p elastic cross section to better than 2% over a Q2 range of 7 − 14 GeV2. From 2015 to 2016, the e − p elastic cross section was measured over a wide range of Q2 from 0.66 − 12.56 GeV2 at …

Determination Of The Kinematics Of The Qweak Experiment And Investigation Of An Atomic Hydrogen Møller Polarimeter, Valerie Marie Gray

Dissertations, Theses, and Masters Projects

The Qweak experiment has tested the Standard Model through making a precise measurement of the weak charge of the proton (QpW). This was done through measuring the parity-violating asymmetry for polarized electrons scattering off of unpolarized protons. The parity-violating asymmetry measured is directly proportional to the four-momentum transfer (Q^2) from the electron to the proton. The extraction of QpW from the measured asymmetry requires a precise Q^2 determination. The Qweak experiment had a Q^2 = 24.8 ± 0.1 m(GeV^2) which achieved the goal of an uncertainty of ≤ 0.5%. From the measured asymmetry and Q^2 , QpW was determined to …

Studies Of Molecular Dynamics Of Fmoc Amino Acids Using Solid State Deuteron Nuclear Magnetic Resonance Spectroscopy, Wei Xu

Dissertations, Theses, and Masters Projects

The purpose of devising and validating models for intramolecular motions for FMOC amino acids is to quantify side chain motion in proteins which plays an important role in understanding biological structure function relations of proteins. In this thesis, spin lattice relaxation times (Ti) of FMOC amino acids were m easured under both static and magic angle spinning (MAS) condition at variable tem peratures. Lower activation energies of the relaxation times than the normal amino acids observed indicate a less sterically crowded environment for the rotation methyl group. A three-site jump model for the methyl group w as developed to fit …

Some Properties Of Meson Excited States From Lattice Qcd, Ekaterina V. Mastropas

Dissertations, Theses, and Masters Projects

The work presented here is devoted to the calculations of the decay constants of the pion and its excited states. All calculations were carried out in the framework of lattice quantum chromodynamics, a well-established formalism of strong interactions enabling the ab initio solution of the theory. After a short introduction and review of the fundamental approaches and methods commonly used in lattice QCD, I provide a detail description of the numerical simulations which were performed at three values of the pion mass between 400 and 700 MeV, using an anisotropic clover fermion action with three flavors of quarks. The results …

Dark Matter In The Heavens And At Colliders: Models And Constraints, Reinard Primulando

Dissertations, Theses, and Masters Projects

In this dissertation, we investigate various aspects of dark matter detection and model building. Motivated by the cosmic ray positron excess observed by PAMELA, we construct models of decaying dark matter to explain the excess. Specifically we present an explicit, TeV-scale model of decaying dark matter in which the approximate stability of the dark matter candidate is a consequence of a global symmetry that is broken only by instanton-induced operators generated by a non-Abelian dark gauge group. Alternatively, the decaying operator can arise as a Planck suppressed correction in a model with an Abelian discrete symmetry and vector-like states at …

Measurement Of Single And Double Spin Asymmetries In P(E, E' Pi(+/-,0))X Semi-Inclusive Deep-Inelastic Scattering, Sucheta Shrikant Jawalkar

Dissertations, Theses, and Masters Projects

Measurements in the late 1980s at CERN revealed that quark spins account for a small fraction of the proton's spin. This so-called spin crisis spurred a number of new experiments to identify the proton's silent spin contributors, namely, the spin of the gluons, which hold the quarks together, and the orbital angular momentum of both quarks and gluons. One such experiment was eg1-dvcs at the Thomas Jefferson National Accelerator Facility in Newport News, Va., which ran in 2009 and collected approximately 19 billion electron triggers for hydrogen. I will present new measurements of the single and double-spin asymmetries ALU, AUL …

The First Direct Measurement Of The Weak Charge Of The Proton, John Poague Leckey Iv

Dissertations, Theses, and Masters Projects

Qweak is an experiment currently running at the Thomas Jefferson National Accelerator Facility that uses parity-violating elastic electron-proton scattering to measure the weak charge of the proton QPweak . Longitudinally polarized electrons are scattered off a liquid hydrogen target and pass through a toroidal-field magnetic spectrometer. This experiment is a sensitive test for physics beyond the Standard Model, as QPweak is well predicted in the Standard Model. This dissertation describes the first direct measurement of QPweak . The precision that will be generated by the final 4% measurement will allow the probing of certain classes of new physics up to …

Parity-Violating Asymmetry In The Nucleon To Delta Transition: A Study Of Inelastic Electron Scattering In The G0 Experiment, Carissa Lee Capuano

Dissertations, Theses, and Masters Projects

The parity-violating asymmetry arising from inelastic electron scattering at backward angle (∼ 95??) near the Delta resonance has been measured for both hydrogen and deuterium targets as part of the G 0 experiment. For Q2 = 0.34 (GeV/c) 2 and W = 1.18 GeV, the asymmetries were found to be AHinel=-33.4+/-5 .3stat+/-5 .1sysppm, ADinel=-43.6+/-1 4.6stat+/- 6.2sysppm. .;From the hydrogen asymmetry, the axial transition form factor, GAND , can be extracted. GAND is related to probability of the quark spin-flip that occurs as the proton transitions to the Delta. From the measured asymmetry, the form factor is found to be GAND=-0.046+/- …

A Measurement Of The Neutron Electric Form Factor At Very Large Momentum Transfer Using Polarized Electrons Scattering From A Polarized Helium-3 Target, Aidan Michael Kelleher

Dissertations, Theses, and Masters Projects

Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q2 and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized 3He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. GEn was measured …

Hadron Structure From Holographic Qcd, Zainul Abidin

Dissertations, Theses, and Masters Projects

The AdS/CFT correspondence relates a strongly coupled gauge theory in four dimensional space-time with a weakly coupled gravity theory in five dimensional space-time. This correspondence provides a way to access the strongly coupled regime of a gauge theory via a perturbative approach in its gravity dual theory. In this dissertation, the gravity dual of Quantum Chromodynamics (QCD) is discussed. The so-called bottom-up approach (AdS/QCD) successfully reproduces the low energy observables at 10-20% accuracy.;An AdS/QCD model with two flavors of quarks is considered, assuming isospin symmetry. Pions and rho mesons masses and decay constants are obtained. We calculate the stress tensor, …

Ultraviolet Sources For Advanced Applications In The Vacuum Uv And Near Uv, Sheng Peng

Dissertations, Theses, and Masters Projects

This dissertation documents a systematic study consisting of experimental investigations and theoretical analyses of intense ultraviolet sources in VUV and near-UV. Some engineering issues regarding two prototypes of electrodeless lamps using rf and microwave are discussed.;Various excimers that produce intense UV light are investigated, including: (1) A benchmark Xe2 excimer which has been proven to be very efficient in our novel rf capacitively coupled discharge lamp; (2) A rarely studied excimer, KrI, which suffers from predissociation and was reported to be very weak or invisible by most of other studies; (3) XeI excimer whose emission dominates around 253 nm and …

Dual Energy Scanning Beam X -Radiography, Randolph Frank Wojcik

Dissertations, Theses, and Masters Projects

Dual energy X-radiography is a method first developed in the mid-1970's by which one uses the information contained in the energy spectrum of the transmitted X-ray flux through an object. With this information one can distinguish the types of materials present in a radiograph and thus allow a computer to subtract them from the image enhancing the contrast of the remaining materials. Using this method, one can see details, which would have been hidden by overlying structures of other materials such as seen in radiographs of parts, made up of mixtures of metals and composites. There is also great interest …

Radiation-Induced Luminescence In Terbium-Doped Silicate Glasses, Michael Stuart West

Dissertations, Theses, and Masters Projects

The purpose of this study is to characterize radiation-induced luminescence of terbium-doped silicate glasses. Experiments performed investigated the optical properties, isothermal time-evolution, and temperature dependence of the radiation-induced luminescence of two commercially available terbium-doped glasses. A problem common to this type of glass is the persistent luminescence, or afterglow, that occurs following the end of excitation from an external source of radiation. While the processes that govern characteristic luminescence of rare earth ions, including terbium, are well understood, the processes that give rise to afterglow in doped glasses are not. Identifying the source of long-term luminescence is essential for controlling …

Synthesis And Characterization Of Boron-Containing Polymeric Materials For Neutron Shielding Applications, Michael B. Glasgow

Dissertations, Theses, and Masters Projects

The development of boron-containing polymeric materials for neutron shielding applications was undertaken. Three types of materials were characterized for physical and thermal properties: boron powder-filled epoxy composites, carborane polyamides having boron chemically bonded into the polymer, and boron-loaded polyimide thin films. Addition of amorphous submicron boron powder did not affect significantly the thermal performance of the epoxy. The 17% boron loading produced a 26% increase in compressive failure strength and a 68% increase in the compressive modulus. 0.125 inch thick specimens containing 17% boron absorbed 92% of incident neutrons from a 5-Curie Pu/Be source compared with {dollar}<{dollar}1% for the neat epoxy. Dispersion of the boron in the epoxy was improved with the addition of larger size crystalline boron powders. Carborane polyamides containing up to 35% boron were thermally stable up to 400{dollar}\sp\circ{dollar}C in air. The polymers had hydrogen/boron ratios from 2.0 to 3.8 and were soluble in several organic solvents. Polymer solutions were processed into clear, colored thin films. Boron-filled polyamic acid solutions of a PMDA-ODA polyimide containing up to 10% boron were processed into thin films. Neutron absorption of the opaque films measured in a 5-Curie Pu/Be neutron source was linear with boron concentration and film thickness. The fraction of neutrons absorbed varied linearly with boron concentration and film thickness. The applicability of boron-containing materials to the aerospace, nuclear power and accelerator industries was investigated.

A Comparison Of (P,2n) And (P,Pn) Reactions On Cerium-140 At Intermediate Energies, Thomas Jean Ruth

Dissertations, Theses, and Masters Projects

No abstract provided.