Parity-violation in Elastic Electron Scattering: A First Measurement of the Parity-violating Asymmetry at Q2
Parity-violation in Elastic Electron Scattering: A First Measurement of the Parity-violating Asymmetry at Q2

Author: Stephanie L. Bailey

Publisher:

Published: 2007

Total Pages: 189

ISBN-13: 9780549078883

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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.

Measurement of the Parity Violating Asymmetry A.
Measurement of the Parity Violating Asymmetry A.

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Published: 1998

Total Pages: 5

ISBN-13:

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The weak pion-nucleon coupling constant H{sub {pi}}1 remains poorly determined, despite many years of effort. The recent measurement of the 133Cs anapole moment has been interpreted to give a value of H{sub {pi}}1 almost an order of magnitude larger than the limit established in the 18F parity doublet experiments. A measurement of the gamma ray directional asymmetry A{sub {gamma}} for the capture of polarized neutrons by hydrogen has been proposed at Los Alamos National Laboratory. This experiment will determine H{sub {pi}}1 independent of nuclear structure effects. However, since the predicted asymmetry is small, A{sub {gamma}} (approximately) 5 x 10−8, systematic effects must be reduced to

Measurement of the Parity-Violating Asymmetry in Deep Inelastic Scattering at JLab 6 GeV.
Measurement of the Parity-Violating Asymmetry in Deep Inelastic Scattering at JLab 6 GeV.

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Published: 2013

Total Pages: 180

ISBN-13:

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The parity-violating asymmetry in deep inelastic scattering (PVDIS) offers us a useful tool to study the weak neutral couplings and the hadronic structure of the nucleon, and provides high precision tests on the Standard Model. During the 6 GeV PVDIS experiment at the Thomas Jefferson National Accelerator Facility, the parity-violating asymmetries A{sub PV} of a polarized electron beam scattering off an unpolarized deuteron target in the deep inelastic scattering region were precisely measured at two Q2 values of 1.1 and 1.9 (GeV/c)2. The asymmetry at Q2=1.9 (GeV/c)2 can be used to extract the weak coupling combination 2C2u - C2d, assuming the higher twist effect is small. The extracted result from this measurement is in good agreement with the Standard Model prediction, and improves the precision by a factor of five over previous data. In addition, combining the asymmetries at both Q2 values provides us extra knowledge on the higher twist effects. The parity violation asymmetries in the resonance region were also measured during this experiment. These results are the first APV data in the resonance region beyond the [Delta] (1232). They provide evidence that the quark hadron duality works for APV at the (10-15)% level, and set constraints on nucleon resonance models that are commonly used for background calculations to other parity-violating electron scattering measurements.

Parity Violation in Elastic Electron Scattering
Parity Violation in Elastic Electron Scattering

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Published: 2007

Total Pages:

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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 Q2 = 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 Q2 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 fi.

Measurement of the Parity-violating Asymmetry in Inclusive Electroproduction of [pi]- Near the Delta0 Resonance
Measurement of the Parity-violating Asymmetry in Inclusive Electroproduction of [pi]- Near the Delta0 Resonance

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Published: 2012

Total Pages:

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The parity-violating (PV) asymmetry of inclusive [pi]- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasi-free photoproduction off the neutron via the [Delta]0 resonance. In the context of heavy-baryon chiral perturbation theory (HB[chi]PT), this asymmetry is related to a low energy constant d[Delta]- that characterizes the parity-violating [gamma]N[Delta] coupling. Zhu et al. calculated d[Delta]- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A[gamma]- = -5.2 to +5.2 ppm. The measurement performed in this work leads to A[gamma]- = -0.36 " 1.06 " 0.37 " 0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to Vud/Vus. The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-[Delta] axial transition form-factors using PV electron scattering.

Measurement of the Parity Violating Asymmetry in Elastic Electron Scattering Off 208Pb
Measurement of the Parity Violating Asymmetry in Elastic Electron Scattering Off 208Pb

Author: Jonathan William Wexler

Publisher:

Published: 2014

Total Pages: 175

ISBN-13:

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The Lead Radius Experiment (PREX) was carried out in order to provide a model independent measurement of the RMS radius square root r2 of the neutron distribution in the 208Pb nucleus. The parity-violating scattering asymmetry for longitudinally polarized 1.06 GeV electrons from an unpolarized 208Pb target was measured at Q2 = 0.00880 GeV2. This measurement was performed by the PREX collaboration in Hall A at Jefferson Laboratory in Newport News, VA, between March and June, 2010. The electron detectors used in this measurement were designed and fabricated by University of Massachusetts-Amherst and Smith College. The resulting parity-violating asymmetry was measured as APV = 656±60(stat.)±14(sys.) ppb. This asymmetry extrapolates to a difference in radii between the nuclear neutron and proton distributions of square root r2n - square root r2p =0.33 +0.16 -0.18 fm.

Measurement of Parity-violating Asymmetry in Electron-deuteron Inelastic Scattering
Measurement of Parity-violating Asymmetry in Electron-deuteron Inelastic Scattering

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Published: 2015

Total Pages:

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The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.

A Measurement of the Parity-Violating Asymmetry in Aluminum and Its Contribution to a Measurement of the Proton's Weak Charge
A Measurement of the Parity-Violating Asymmetry in Aluminum and Its Contribution to a Measurement of the Proton's Weak Charge

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Published: 2016

Total Pages:

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The Q_weak experiment, which ran at the Thomas Jefferson National Accelerator Facility, made a precision measurement of the proton's weak charge, Q^p_W. The weak charge is extracted via a measurement of the parity-violating asymmetry in elastic electron-proton scattering from hydrogen at low momentum transfer (Q^2=0.025 GeV^2). This result is directly related to the electroweak mixing angle, sin^2(Theta_W), a fundamental parameter in the Standard Model of particle physics. This provides a precision test sensitive to new, as yet unknown, fundamental physics. This dissertation focuses on two central corrections to the Q_weak measurement: the target window contribution and sub-percent determination of the electron beam polarization. The aluminum target windows contribute approximately 30% of the measured asymmetry. Removal of this background requires precise measurements of both the elastic electron-aluminum scattering rate and its parity-violating asymmetry. The results reported here are the most precise measurement of the Q_weak target dilution and asymmetry to date. The parity-violating asymmetry for the aluminum alloy was found to be 1.6174 +/- 0.0704 (stat.) +/- 0.0113 (sys.) parts-per-million. The first sub-percent precision polarization measurements made from the Hall C Moller polarimeter are also reported, with systematic uncertainties of 0.84%.

Measurement of the Parity Violating Asymmetry in Elastic Electron Scattering Off 208Pb
Measurement of the Parity Violating Asymmetry in Elastic Electron Scattering Off 208Pb

Author:

Publisher:

Published: 2014

Total Pages: 197

ISBN-13:

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The Lead Radius Experiment (PREX) was carried out in order to provide a model-independent measurement of the RMS radius sqrt(r-2/n) of the neutron distribution in the 208Pb nucleus. The parity-violating scattering asymmetry for longitudinally polarized 1.06 GeV electrons from an unpolarized 208Pb target was measured at Q2 = 0.00880 GeV2. This measurement was performed by the PREX collaboration in Hall A at Jefferson Laboratory in Newport News, VA, between March and June, 2010. The electron detectors used in this measurement were designed and fabricated by University of Massachusetts-Amherst and Smith College. The resulting parity-violating asymmetry was measured as APV = 656±60(stat.)±14(sys.) ppb. This asymmetry extrapolates to a difference in radii between the nuclear neutron and proton distributions of sqrt(r-2/n)-sqrt(r-2/p)=0.33^+0.16/-0.18 fm.

Measurement of the Parity-Violating Asymmetries in Electron-Deuteron Scattering in the Nucleon Resonance Region
Measurement of the Parity-Violating Asymmetries in Electron-Deuteron Scattering in the Nucleon Resonance Region

Author:

Publisher:

Published: 2013

Total Pages: 7

ISBN-13:

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We report on parity-violating asymmetries in the nucleon resonance region measured using 5 - 6 GeV longitudinally polarized electrons scattering off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the [Delta](1232), and provide a verification of quark-hadron duality in the nucleon electroweak [gamma] Z interference structure functions at the (10-15)% level. The results are of particular interest to models relevant for calculating the [gamma] Z box-diagram corrections to elastic parity-violating electron scattering measurements.