Strange quark contributions to nucleon electric and magnetic form factors from parity-violating electron scattering asymmetries in the backward angle g0 experiment

The G0 collaboration has measured parity-violating asymmetries in elastic electron-proton and quasi-elastic electron-deuteron scattering at Q^2 = 0.22, 0.63 GeV^2. These asymmetries are sensitive to strange quark contributions to electric and magnetic properties of the nucleon, as well as to the axial current of the nucleon. The measurements were made using the polarized beam at Jefferson Laboratory by detecting electrons scattered at ~110 degrees from liquid targets. Together with previous results from the G0 forward angle measurement, the form factors which characterize the strange electric, strange magnetic and axial contributions were found to be G^{s}_{E}(0.221 GeV^2)= -0.0142305 +/- 0.035562 +/- 0.0181952 +/-0.0176497 G^{s}_{M}(0.221 GeV^2)=0.0833777 +/- 0.18337 +/- 0.0854892 +/- 0.0780912 G^{e}_{A}(0.221 GeV^2)=-0.501236 +/- 0.317127 +/- 0.193005 +/- 0.0878386 G^{s}_{E}(0.628 GeV^2)=0.110227 +/-0.0488068 +/- 0.0296044 +/- 0.0236998 G^{s}_{M}(0.628 GeV^2)=-0.12354 +/- 0.10953 +/- 0.0614285 +/- 0.0316972 G^{e}_{A}(0.628 GeV^2)=-0.197329 +/- 0.425414 +/- 0.256755 +/- 0.0948741 with statistical, point-to-point systematic and global systematic uncertainties given respectively. These results indicate small (<10%) strange quark contributions to the charge and magnetic nucleon form factors at the measured momentum transfers and are also consistent with a signficant reduction in the magnitude of the effective axial form factor compared with that measured in neutrino scattering experiments, providing the first experimental information on the nucleon anapole moment.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• Muether, Mathew O.

Contributors dc:contributor

• Beck, Douglas H.
• Peng, Jen-Chieh
• Willenbrock, Scott S.
• Abbamonte, Peter M.

• Form Factors
• Strangeness
• G0
• parity-violating electron scattering

Statement dc:rights

• Copyright 2010 Mathew Oliver Muether

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/16038

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/16038