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A Precision Measurement of the Weak Mixing Angle in Møller Scattering at Low Q₂


Jones, Gary Mark (2004) A Precision Measurement of the Weak Mixing Angle in Møller Scattering at Low Q₂. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/S506-PZ85.


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 Moller 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 Moller 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).

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:electron-electron; GWS; stanford linear accelerator
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hughes, Emlyn Willard
Thesis Committee:
  • Hughes, Emlyn Willard (chair)
  • Hitlin, David G.
  • Kamionkowski, Marc P.
  • Golwala, Sunil
Defense Date:19 May 2004
Record Number:CaltechETD:etd-05272004-172049
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2138
Deposited By: Imported from ETD-db
Deposited On:28 May 2004
Last Modified:20 Jan 2021 23:18

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