Doctor of Philosophy (Ph.D.)
The goal of Experiment E04-115 (the G0 backward angle measurement) at Jefferson Lab is to investigate the contributions of strange quarks to the fundamental properties of the nucleon. The experiment measures parity-violating asymmetries in elastic electron scattering off hydrogen and quasielastic electron scattering off deuterium at backward angles at Q2 = 0.631 (GeV/c)2 and Q 2 = 0.232 (GeV/c)2. The backward angle measurement represents the second phase of the G0 experiment. The first phase, Experiment E00-006 (the G0 forward angle experiment), measured parity-violating asymmetries in elastic electron scattering off hydrogen at forward angles over a Q 2 range of 0.1-1.0 (GeV/c)2. The experiments used a polarized electron beam and unpolarized hydrogen and deuterium liquid targets. From these measurements, along with the electromagnetic form factors, one can extract the contribution of the strange quark to the proton's charge and magnetization distributions.;This thesis represents a first measurement of a parity-violating asymmetry in elastic electron scattering at Q2 = 0.631 (GeV/c) 2 off hydrogen at backward angles. This work is based on data obtained during the first part of the run, beginning in March 2006 and ending in May 2006. During this period, a total of 15 C of beam charge was accumulated. The total accumulated charge represents about 15% of the 110 C which was proposed for this Q2. The measured asymmetry is A = (-47.4 +/- 7.1 +/- 5.9 +/- 11.8) ppm, where the first uncertainty is due to statistics, the second uncertainty is systematic, and the third uncertainty is associated with the blinding factor. This result is consistent with a zero contribution from the strange quarks. The helicity-correlated beam properties and slopes are under adequate control for the final precision of the experiment.
© The Author
Bailey, Stephanie L., "Parity-violation in elastic electron scattering: A first measurement of the parity-violating asymmetry at Q2 = 0.631 (GeV/c)2 at backward angle" (2007). Dissertations, Theses, and Masters Projects. Paper 1539623510.