Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N → Δ Transition
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Abstract
Qweak will determine the weak charge of the proton, Q p{sub W}, via an asymmetry measurement of parity-violating elastic electron-proton scattering at low four momentum transfer to a precision of 4%. Q p W has a firm Standard Model prediction and is related to the weak mixing angle, sin 2 Φ W, a well-defined Standard Model parameter. Qweak will probe a subset of new physics to the TeV mass scale and test the Standard Model. The details of how this measurement was performed and the analysis of the 25% elastic dataset will be presented in this thesis. Also, an analysis of an auxiliary measurement of the parity-violating asymmetry in the N → Δ transition is presented. It is used as a systematic inelastic background correction in the elastic analysis and to extract information about the hadronic parity violation through the low energy constant, d Δ. The elastic asymmetry at Q 2 = 0.0252 ± 0.0007 GeV 2 was measured to be A ep = -265 ± 40 ± 22 ± 68 ppb (stat., sys., and blinding). Extrapolated to Q 2 = 0, the value of the proton's weak charge was measured to be Q p W = 0.077 ± 0.019more »
- Authors:
-
- Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
- Publication Date:
- Research Org.:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1057572
- Report Number(s):
- JLAB-PHY-12-1677; DOE/OR/23177-2406
- DOE Contract Number:
- AC05-06OR23177
- Resource Type:
- Thesis/Dissertation
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Citation Formats
Leacock, John D. Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N → Δ Transition. United States: N. p., 2012.
Web. doi:10.2172/1057572.
Leacock, John D. Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N → Δ Transition. United States. doi:10.2172/1057572.
Leacock, John D. Tue .
"Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N → Δ Transition". United States. doi:10.2172/1057572. https://www.osti.gov/servlets/purl/1057572.
@article{osti_1057572,
title = {Measuring the Weak Charge of the Proton and the Hadronic Parity Violation of the N → Δ Transition},
author = {Leacock, John D.},
abstractNote = {Qweak will determine the weak charge of the proton, Qp{sub W}, via an asymmetry measurement of parity-violating elastic electron-proton scattering at low four momentum transfer to a precision of 4%. QpW has a firm Standard Model prediction and is related to the weak mixing angle, sin2 ΦW, a well-defined Standard Model parameter. Qweak will probe a subset of new physics to the TeV mass scale and test the Standard Model. The details of how this measurement was performed and the analysis of the 25% elastic dataset will be presented in this thesis. Also, an analysis of an auxiliary measurement of the parity-violating asymmetry in the N → Δ transition is presented. It is used as a systematic inelastic background correction in the elastic analysis and to extract information about the hadronic parity violation through the low energy constant, dΔ. The elastic asymmetry at Q2 = 0.0252 ± 0.0007 GeV2 was measured to be Aep = -265 ± 40 ± 22 ± 68 ppb (stat., sys., and blinding). Extrapolated to Q2 = 0, the value of the proton's weak charge was measured to be QpW = 0.077 ± 0.019 (stat. and sys.) ± 0.026 (blinding). This is within 1 σ of the Standard Model prediction of QpW = 0.0705 ± 0.0008. The N → Δ inelastic asymmetry at Q2 = 0.02078 ± 0.0005 GeV2 and W = 1205 MeV was measured to be Ainel = -3.03 ± 0.65 ± 0.73 ± 0.07 ppm (stat., sys., and blinding). This result constrains the low energy constant to be dΔ = 5.8 ± 22gπ, and, if the result of the G0 experiment is included, dΔ = 5.8 ± 17gπ. This result rules out suggested large values of dΔ motivated by radiative hyperon decays. The elastic measurement is the first direct measurement of the weak charge of the proton while the inelastic measurement is only the second measurement of the neutral current excitation of the Δresonance. It is currently the best constraint for the low energy constant, dΔ.},
doi = {10.2172/1057572},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Oct 16 00:00:00 EDT 2012},
month = {Tue Oct 16 00:00:00 EDT 2012}
}