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Type of Document	Dissertation
Author	Jones, G. Mark
Author's Email Address	markj AT slac.stanford.edu
URN	etd-05272004-172049
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-05272004-172049
Title	A precision measurement of the weak mixing angle in Møller scattering at low Q2
Degree	PhD
Option	Physics
Advisory Committee	Advisor Name Title Emlyn Hughes Committee Chair David Hitlin Committee Member Marc Kamionkowski Committee Member Sunil Golwala Committee Member
Keywords	stanford linear accelerator electron-electron GWS
Date of Defense	2004-05-19
Availability	unrestricted
Abstract The electroweak theory has been probed to a high level of precision at the mass scale of the Zo through the joint contributions of LEP at CERN and the SLC at SLAC. The E158 experiment at SLAC complements these results by measuring the weak mixing angle at a Q2 of 0.026 (GeV/c)2, far below the weak scale. The experiment utilizes a 48 GeV longitudinally polarized electron beam on unpolarized atomic electrons in a target of liquid hydrogen to measure the parity-violating asymmetry APV in Møller scattering. The tree-level prediction for APV is proportional to 1-4sin2θW. Since sin2θW is approximately 0.25, the effect of radiative corrections is enhanced, allowing the E158 experiment to probe for physics effects beyond the Standard Model at the TeV scale. This work presents the results from the first two physics runs of the experiment, covering data collected in the year 2002. The parity-violating asymmetry APV was measured to be APV = -158 ppb ± 21 ppb (stat) ± 17 ppb (sys). The result represents the first demonstration of parity violation in Møller scattering. The observed value of APV corresponds to a measurement of the weak mixing angle of sin2θWeff = 0.2380 ± 0.0016 (stat) ± 0.0013 (sys), which is in good agreement with the theoretical prediction of sin2θWeff = 0.2385 ± 0.0006 (theory).
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