ORCID ID

0000-0001-7573-1420

Date Awarded

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physics

Advisor

David S Armstrong

Committee Member

Wouter Deconinck

Committee Member

Todd Averett

Committee Member

Mark Dalton

Committee Member

Wally Melnitchouk

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.

DOI

http://dx.doi.org/10.21220/s2-km75-4a73

Rights

© The Author

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