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Probe of Electroweak Interference Effects in Non-Resonant Inelastic Electron-Proton Scattering
Dowd, James Franklyn
Dowd, James Franklyn
Abstract
The Qweak collaboration at Jefferson Lab made the first direct measurement of the proton's weak charge, Q_W^p, via a measurement of the parity-violating asymmetry in elastic e ⃑p scattering with low four-momentum transfer. to meet the high-precision goals, energy-dependent electroweak radiative corrections were applied to the measured asymmetry. The γZ box, □_γZ, where a photon and a Z-boson are simultaneously exchanged, was the most problematic of these corrections. It could not be calculated through the same perturbative methods as the rest of the corrections. The □_γZ correction depends on theoretical models of the γZ interference structure functions, F_1,2^γZ, for which there are almost no data. Presented in this dissertation are the results from a specialized run of the Qweak experiment. Using the Qweak apparatus, with modifications, a measurement of the parity-violating asymmetry of non-resonant inelastic e ⃑p scattering was made with 3.35 GeV incident electrons. The apparatus was tuned to inelastic e ⃑p scattering with an average W=2.33 GeV and Q^2=0.082 GeV^2, in order to test the theoretical models used to predict the □_γZ radiative correction. The final inelastic asymmetry, after correcting for beam polarization and backgrounds, was found to be A_phys= -13.5±4.4 ppm, in agreement with theoretical predictions. This measurement provides important experimental validation of the theoretical methods used to calculate the □_γZ radiative correction. Additionally, this measurement provides useful experimental constraints on the F_1,2^γZ interference structure functions used in those theoretical models.
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2018-09-11
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Physics
DOI
http://dx.doi.org/10.21220/s2-km75-4a73