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Constraining G(s)E and G(s)M Via Parity-Violating Electron Scattering

Posted on:2011-01-08Degree:Ph.DType:Thesis
University:University of VirginiaCandidate:Snyder, Ryan AlanFull Text:PDF
GTID:2448390002955019Subject:Physics
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This thesis reports on the 2005 HAPPEX parity-violating measurements APV in elastic scattering of 3 GeV electrons off hydrogen and 4He targets at ⟨thetalab⟩ ≈ 6.0° carried out in Hall A at the Thomas Jefferson National Accelerator Facility in Newport News, VA. The 4He result is AHePV = +6.40 +/- 0.23 (stat) +/- 0.12 (syst) ppm. The hydrogen result is AHPV = -1.60 +/- 0.12 (stat) +/- 0.05 (syst) ppm. These results significantly improve the constraints on the electric and magnetic strange form factors GsE and GsM . We extracted GsE = -0.02 +/- 0.014 (stat) +/- 0.007 (syst) at ⟨ Q²⟩ = 0.077 GeV2 from the 4He result and the linear combination GsE + 0.088 GsM = 0.007 +/- 0.011 (stat) +/- 0.004 (syst) +/- 0.005 (FF) at ⟨Q²⟩ = 0.109 GeV² from hydrogen. These results provide new limits on the role of strange quarks in the nucleon charge and magnetization distributions.;This thesis reports on both the 4He and hydrogen analysis of the 2005 data set with a particular focus on the background contamination for each measurement. An additional focus here is given to understanding and minimizing helicity-correlated asymmetries on the electron beam, systematic errors we needed to control at levels well below that of the measured parity-violating asymmetries APV.
Keywords/Search Tags:Parity-violating, Hydrogen, Syst
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