Virginia Tech
Precision Measurement of the Proton's Weak Charge using Parity-Violating Electron Scattering
Abstract
dc:description.abstractThe Qweak experiment has precisely determined the weak charge of the proton Qp w by measuring the parity-violating asymmetry in elastic electron-proton scattering at a low momentum transfer of Q2 = 0.0249 (GeV/c)2 . Qpw has a definite prediction in the Standard Model, and a value of sin2 θW can be extracted from it for comparison with other neutral current observables. Qweak measured the weak charge of the proton to be Qpw(P V ES) = 0.0719 ± 0.0045, which is consistent with the Standard Model value of Qp w(SM) = 0.0708 ± 0.0003. Qweak ran at the Thomas Jefferson National Accelerator Facility for two and a half years and was installed in experimental Hall C. A 180µA beam of longitudinally polarized electrons at 1.16 GeV scattered off a liquid hydrogen target of unpolarized protons. The electrons were collimated to an acceptance of 5.8◦ to 11.6◦ and then passed through a magnetic spectrometer and onto quartz Čerenkov detector bars. A detailed description of the theory and motivation behind the Qweak experiment is given. An overview of the Qweak apparatus and an in-depth discussion of the luminosity monitor performance is presented. A general overview of the Qweak analysis is also presented, with a focus on the beamline background correction, the nonlinearity measurement, and the simulation to constrain error for a rescattering effect. Also detailed here is the final, unblinded Qweak result, which determined Qpw to 6.2% and provided the highest precision measurement of sin2θW at low energy.
Degree
thesis:*- Name thesis:degree_name
- PHD
- Level thesis:degree_level
- doctoral
- Discipline thesis:degree_discipline
- Physics
- Department dc:contributor.department
- Physics
- Grantor dc:publisher
- Virginia Tech
- Year dc:date.issued
- 2017
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Duvall, Wade Sayer
- Chair dc:contributor.committeechair
-
- Pitt, Mark L.
- Committee members dc:contributor.committeemember
-
- Huber, Patrick
- Simonetti, John H.
- Piilonen, Leo E.
- Sharpe, Eric R.
Subjects
dc:subject × 8Rights
dc:rights- Statement dc:rights
-
- In Copyright
- Licence dc:rights.uri
Identifiers
dc:identifier.*- Dc Identifier Other
- vt_gsexam:13445
- OAI identifier oai:identifier
- oai:vtechworks.lib.vt.edu:10919/89476