Title page for ETD etd-05112010-155435


Type of Document Dissertation
Author Mammei, Juliette Mae
URN etd-05112010-155435
Title Parity-Violating Elastic Electron Nucleon Scattering: Measurement of the Strange Quark Content of the Nucleon and Towards a Measurement of the Weak Charge of the Proton
Degree PhD
Department Physics
Advisory Committee
Advisor Name Title
Pitt, Mark L. Committee Chair
Blecher, Marvin Committee Member
Mizutani, Tetsuro Committee Member
Schmittmann, Beate Committee Member
Vogelaar, Robert Bruce Committee Member
Keywords
  • Strange quark
  • transverse
  • beam normal single spin asymmetry
  • G0
  • Qweak
Date of Defense 2010-04-30
Availability unrestricted
Abstract
The experiments discussed in this thesis exploit parity violation in elastic electron proton

scattering in order to measure properties of the nucleon. Both experiments make use of

the high quality, highly polarized electron beam available at Thomas Jeff erson National

Accelerator Facility. Qweak will measure the weak mixing angle, sin2θW, via a measurement

of the weak charge of the proton, at a four-momentum transfer, Q2~0.026 GeV2/c2. The

precision of this measurement gives Qweak access to new physics at the scale of 2.3 TeV,

making it a test of the standard model. The G0 experimental program provides the fully

separated contributions of the strange quark to the charge and magnetization distributions of

the nucleon at two di fferent values of four-momentum transfer, Q2 ~ 0.22 and 0.63 GeV2/c2. The measurement of the strange quark content of the proton in the G0 experimental program

and other parity-violating electron scattering experiments provides a measurement of the

hadronic contribution to the asymmetry in Qweak.

In addition, G0 was able to measure the parity-conserving beam normal single spin

asymmetries that provide a measurement of the imaginary part of two photon exchange.

The measurement of this asymmetry is necessary to understand the systematic contribution

to measurements of parity-violating asymmetries, but it is also an important physics result.

Recent theoretical work has shown that higher order radiative eff ects, such as two photon

exchange, may be able to explain discrepancies between experiments which measure the ratio

of the electric and magnetic form factors of the proton. The measurement of the transverse or

beam normal single spin asymmetries provides a benchmark for theories that estimate the size

of radiative corrections that are important for precision electroweak scattering experiments

such as those described in this thesis. The results of the measurement of the transverse

asymmetries at backward angles in G0 are presented at the two values of Q2 ~ 0.22 and 0.63 GeV2/c2 for hydrogen. Results for deuterium, which can provide the first measurements of the beam normal single spin asymmetries on the neutron, are also presented.

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