Dissertation/Thesis Abstract

The First Determination of the Proton's Weak Charge Through Parity-Violating Asymmetry Measurements in Elastic e + p and e + Al Scattering
by Myers, Katherine E., Ph.D., The George Washington University, 2012, 229; 3499836
Abstract (Summary)

The Qweak experiment at Jefferson Laboratory will make a 4% measurement of the proton's weak charge, Qp W, by measuring the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer, Q 2 = 0.025 GeV2. This asymmetry is proportional to the weak charge of the proton and can be related to the weak mixing angle, sin2&thetas;W, a parameter in the Standard Model. Qweak will measure the weak mixing angle precisely to 0.3%, challenging predictions of the Standard Model and probing certain types of new physics up to the TeV scale. Details of how this measurement is performed and a preliminary analysis of the first subset of production data are presented in this dissertation. This includes a detailed preliminary analysis of the systematic uncertainties, which includes a preliminary measurement of the asymmetry in elastic electron-aluminum scattering, a significant correction in the experiment. The final asymmetry, corrected for backgrounds and beam polarization, was found to be Aep = −246 ± 40.3 (stat.) ± 29.1 (sys.) ± 68 (blinding factor) parts-per-billion, which results in an extracted weak charge of Qp W = 0.0805 ± 0.0189 (combined stat. and sys.) ± 0.026 (blinding factor), consistent with the Standard Model prediction. Once unblinded, this first result from the Qweak experiment will give a 25% measurement of the proton's weak charge, providing an improved constraint on the weak vector quark coupling combination 2C1u ± C1d.

Indexing (document details)
Advisor: Opper, Allena K., Mack, David J.
Commitee: Beise, Elizabeth J., Briscoe, William J., Feldman, Gerald, Griesshammer, Harald W.
School: The George Washington University
Department: Physics
School Location: United States -- District of Columbia
Source: DAI-B 73/07(E), Dissertation Abstracts International
Subjects: Nuclear physics
Keywords: Elastic electron-proton scattering, Electroweak, Parity-violating asymmetry, Precision measurements, Weak charge
Publication Number: 3499836
ISBN: 978-1-267-24916-6
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