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A Measurement of the Weak Charge of the Proton through Parity Violating Electron Scattering using the Qweak Apparatus: A 21% Result (open access)

A Measurement of the Weak Charge of the Proton through Parity Violating Electron Scattering using the Qweak Apparatus: A 21% Result

After a decade of preparations, the Qweak experiment at Jefferson Lab is making the first direct measurement of the weak charge of the proton, Q^p_W. This quantity is suppressed in the Standard Model making a good candidate for search for new physics beyond the SM at the TeV scale. Operationally, we measure a small (about -0.200 ppm) parity-violating asymmetry in elastic electron-proton scattering in integrating mode while flipping the helicity of the electrons 1000 times per second. Commissioning took place Fall 2010, and we finished taking data in early summer 2012. This dissertation is based on the data taken on an initial two weeks period (Wien0). It will provide an overview of the Qweak apparatus, description of the data acquisition and analysis software systems, and final analysis and results from the Wien0 data set. The result is a 16% measurement of the parity violating electron-proton scattering asymmetry, A = -0.2788 +/- 0.0348 (stat.) +/- 0.0290 (syst.) ppm at Q^2 = 0.0250 +/- 0.0006 (GeV)^2. From this a 21% measurement of the weak charge of the proton, Q_w^p(msr)= +0.0952 +/- 0.0155 (stat.) +/- 0.0131 (syst.) +/- 0.0015 (theory) is extracted. From this a 2% measurement of the weak mixing angle, sin^2theta_W(msr)= …
Date: August 1, 2013
Creator: Beminiwattha, Rakitha
System: The UNT Digital Library
A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup (open access)

A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

The beam normal single spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable of the imaginary part of the two-photon exchange process. Moreover, it is a potential source of false asymmetry in parity violating electron scattering experiments. The Q{sub weak} experiment uses parity violating electron scattering to make a direct measurement of the weak charge of the proton. The targeted 4% measurement of the weak charge of the proton probes for parity violating new physics beyond the Standard Model. The beam normal single spin asymmetry at Q{sub weak} kinematics is at least three orders of magnitude larger than 5 ppb precision of the parity violating asymmetry. To better understand this parity conserving background, the Q{sub weak} Collaboration has performed elastic scattering measurements with fully transversely polarized electron beam on the proton and aluminum. This dissertation presents the analysis of the 3% measurement (1.3% statistical and 2.6% systematic) of beam normal single spin asymmetry in electronproton scattering at a Q2 of 0.025 (GeV/c)2. It is the most precise existing measurement of beam normal single spin asymmetry available at the time. A measurement of this precision helps to improve the theoretical models on beam normal …
Date: August 1, 2013
Creator: Waidyawansa, Dinayadura Buddhini
System: The UNT Digital Library
Two-Photon Exchange E#27;ffects in Elastic Electron-Proton Scattering (open access)

Two-Photon Exchange E#27;ffects in Elastic Electron-Proton Scattering

Two methods, Rosenbluth separation and polarization transfer, can be used to extract the proton form factor ratio #22;mu_p G_Ep/G_Mp, but they do not yield the same results. It is thought that the disagreement is due to two photon exchange corrections to the #27;differential cross sections. High precision proton Rosenbluth extractions were carried out at 102 kinematics points spanning 16 values of momentum transfer Q^2, from 0.40 to 5.76 GeV^2. Reduced cross sections were found to 1.1% or better for Q^2 less than 3 GeV^2, increasing to 4% at 5.76 GeV^2. The form factor ratios were determined to 1:5-3% for Q2 < 1.5 GeV^2, increasing to 9% by 3 GeV^2 and rapidly above. Our data agrees with prior Rosenbluth, improving upon it the 1.0 - 2.0 GeV^2 range to conclusively show a separation from polarization transfer where it had not been certain before. In addition, reduced cross sections at each Q^2 were tested for nonlinearity in the angular variable. Such a departure from linearity would be a signature of two photon exchange effects, and prior data had not been #30;sufficiently precise to show nonzero curvature. Our data begins to hint at negative curvature but does not yet show a significant departure …
Date: August 1, 2013
Creator: Laboratory, Argonne National
System: The UNT Digital Library
Search for New and Unusual Stangonia using CLAS (open access)

Search for New and Unusual Stangonia using CLAS

We perform a survey of the proton, K^+, K^- -3 charged track data, taken by the CLAS detector for the HyCLAS experiment 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.
Date: March 1, 2013
Creator: Saini, Mukesh Satyapraka
System: The UNT Digital Library
Hybrid Nanocomposites for Bolometer Applications (open access)

Hybrid Nanocomposites for Bolometer Applications

Undergraduate thesis studying the properties of amorphous silicon (⍺-Si) and crystalline silicon nanowires (c-Si NWs), focusing on the requirements placed on thin films by bolometers.
Date: May 1, 2013
Creator: Cook, Andrew
System: The UNT Digital Library
Proton form factor ratio, {mu}{sub p}G{sub E}{sup P}/G{sub M}{sup P} from double spin asymmetry (open access)

Proton form factor ratio, {mu}{sub p}G{sub E}{sup P}/G{sub M}{sup P} from double spin asymmetry

The form factors are fundamental properties of the nucleon representing the effect of its structure on its response to electromagnetic probes such as electrons. They are functions of the four-momentum transfer squared Q{sup 2} between the electron and the proton. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton up to Q{sup 2} = 5.66 (GeV/c){sup 2} using the double spin asymmetry with a polarized beam and target. Experiment E07-003 (SANE, Spin Asymmetries of the Nucleon Experiment) was carried out in Hall C at Jefferson Lab in 2009 to study the proton spin structure functions with a dynamically polarized ammonia target and longitudinally polarized electron beam. By detecting elastically scattered protons in the High-Momentum Spectrometer (HMS) in coincidence with the electrons in the Big Electron Telescope Array (BETA), elastic measurements were carried out in parallel. The elastic double spin asymmetry allows one to extract the proton electric to magnetic form factor ratio G{sup p}{sub E}/G{sup p}{sub M} at high-momentum transfer, Q{sup 2} = 5.66 (GeV/c){sup 2}. In addition to the coincidence data, inclusively scattered electrons from the polarized ammonia target were detected by HMS, which allows to …
Date: August 1, 2013
Creator: Pushpakumari, Habarakada L. A.
System: The UNT Digital Library