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[PAST EVENT] Joshua A. Magee, Physics - Oral Exam for the Ph.D.
February 4, 2016
1pm - 3pm
Abstract:
The Q-weak experiment, which ran at the Thomas Jefferson National Accelerator Facility, will make a precision measurement of the proton's weak charge, QWp. The weak charge is extracted via a precision measurement of the parity-violating asymmetry in elastic electron-proton scattering from hydrogen at low momentum transfer (Q^2=0.026 GeV^2). This result is directly related to the electroweak mixing angle, which is a fundamental parameter in the Standard Model of particle physics. This provides a precision test sensitive to possible new, as yet unknown, fundamental physics.
This dissertation focuses on two central corrections to the Q-weak measurement: the target window contribution and sub-percent determination of the electron beam polarization. The aluminum target windows contribute approximately 30% of the measured asymmetry. Removal of this background requires precise measurements of both the elastic electron-aluminum scattering rate and its parity-violating asymmetry. The results reported here are the most precise measurement of the Q-weak target dilution and asymmetry to date. The parity-violating asymmetry for the aluminum alloy was found to be 1.61740.0704 (stat.) 0.0113 (sys.) parts-per-million. The first sub-percent precision polarization measurements made from the Hall C Mller polarimeter are also reported, with systematic uncertainties of 0.84%.
Bio:
Josh Magee grew up in Bridgewater, MA. He graduated from the University of Hartford in 2007 with a degree in mechanical engineering. After working as an engineer for the Hartford Steam Boiler Inspection and Insurance Company, he enrolled at William & Mary. His current work specializes in precision measurements of electroweak observables. Josh and his two boys, Rosencrantz and Tommy, are relocating the San Francisco Bay region, where he recently accepted a position at Lawrence Livermore National Laboratory in the Nuclear and Particle Physics group.
The Q-weak experiment, which ran at the Thomas Jefferson National Accelerator Facility, will make a precision measurement of the proton's weak charge, QWp. The weak charge is extracted via a precision measurement of the parity-violating asymmetry in elastic electron-proton scattering from hydrogen at low momentum transfer (Q^2=0.026 GeV^2). This result is directly related to the electroweak mixing angle, which is a fundamental parameter in the Standard Model of particle physics. This provides a precision test sensitive to possible new, as yet unknown, fundamental physics.
This dissertation focuses on two central corrections to the Q-weak measurement: the target window contribution and sub-percent determination of the electron beam polarization. The aluminum target windows contribute approximately 30% of the measured asymmetry. Removal of this background requires precise measurements of both the elastic electron-aluminum scattering rate and its parity-violating asymmetry. The results reported here are the most precise measurement of the Q-weak target dilution and asymmetry to date. The parity-violating asymmetry for the aluminum alloy was found to be 1.61740.0704 (stat.) 0.0113 (sys.) parts-per-million. The first sub-percent precision polarization measurements made from the Hall C Mller polarimeter are also reported, with systematic uncertainties of 0.84%.
Bio:
Josh Magee grew up in Bridgewater, MA. He graduated from the University of Hartford in 2007 with a degree in mechanical engineering. After working as an engineer for the Hartford Steam Boiler Inspection and Insurance Company, he enrolled at William & Mary. His current work specializes in precision measurements of electroweak observables. Josh and his two boys, Rosencrantz and Tommy, are relocating the San Francisco Bay region, where he recently accepted a position at Lawrence Livermore National Laboratory in the Nuclear and Particle Physics group.