The 18th International Symposium on Spin Physics

October 6-11, 2008
University of Virginia
Charlottesville, VA USA

View Abstract

First Name Kent
Last Name Paschke
Affiliation University of Virginia
Title Sources of Helicity-correlated Electron Beam Asymmetries
Topic Oral
Abstract of 200 words or less
The availability of high current, high polarization electron beams from
laser-driven GaAs photocathodes has enabled a broad program studying
parity violation in electron scattering. Precision measurements of the
tiny (<1 part per million) parity-violating beam-helicity asymmetry are
used to study the structure of nuclei or to test the Standard Model of
electroweak interactions. As these experiments grow ever more precise,
asymmetric beam properties between the two beam helicity states threaten to become the leading source of experimental uncertainty. These helicity-correlated beam asymmetries are predominantly created in the conversion of circularly polarized laser light to a polarized electron beam. In recent experiments at Jefferson Lab, improved techniques for configuring the laser optics of the polarized source have been used to control beam asymmetries to such a level as to be a negligible source of systematic uncertainty. This successful result serves as a promising start for the next generation of parity-violating electron-nuclear scattering measurements, which strive to improve precision by a factor of twenty.