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Author: Paul Souder
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Languages : en
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We review the program of parity violation in the scattering of polarized electrons at JLab. Results are presented from recent experiments measuring the weak form factors, which in turn measure the contribution of strange quarks to the elastic form factors. In addition, we discuss the physics of parity violation in deep inelastic scattering, which will become possible with the upgrade of the JLab energy to 12 GeV.
Author: Paul Souder
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Languages : en
Pages :
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Book Description
We review the program of parity violation in the scattering of polarized electrons at JLab. Results are presented from recent experiments measuring the weak form factors, which in turn measure the contribution of strange quarks to the elastic form factors. In addition, we discuss the physics of parity violation in deep inelastic scattering, which will become possible with the upgrade of the JLab energy to 12 GeV.
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Languages : en
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Experiments on parity violation in electron scattering measure the asymmetry A = [sigma][sub R] - [sigma][sub L]/[sigma][sub R] + [sigma][sub L] where [sigma][sub R(L)] is the cross section for Right(Left) handed longitudinally polarized electrons. This asymmetry arises, in first order, from the interference between photon and Z-boson exchange amplitudes. Experiments make two basic uses of the Z-boson as a probe in electron-quark or electron-nucleon scattering. Historically the first usage was to test the electroweak theory in regions of kinematics where the hadronic structure is sufficiently understood. They discuss the application of higher energies at Jefferson Lab to repeat the SLAC e-D deep inelastic parity violation experiment [1] at a level of precision [approx] 0.5% in sin[sup 2][theta][sub W] which would be a useful constrain on extensions of the Standard Model [2]. The second, more recent usage of the Z-boson probe is to assume the Standard Model is correct at about the 1% level and use this as a unique method to address fundamental issues of nucleon structure, such as: (1) are the strange quarks an important component of the nucleon [3]; (2) In deep inelastic scattering, are the high momentum quarks u or d quarks? To address the first question, they discuss the feasibility of extending the HAPPEX experiment to higher Q[sup 2]. For the second question, they discuss a possible measurement of the ratio of valence quarks d/u in the proton using deep inelastic parity violation.
Author: Xiaochao Zheng
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Languages : en
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The parity-violating asymmetry in e-$^2$H deep inelastic scattering (DIS) can be used to extract the weak neutral-current coupling constants $C_{2q}$. A measurement of this asymmetry at two $Q^2$ values is planned at Jefferson Lab. Results from this experiment will provide a value of $2C_{2u}-C_{2d}$ to a precision of $\pm 0.03$, a factor of eight improvement over our current knowledge. If all hadronic effects can be understood, this results will provide information on possible extensions of the Standard Model, complementary to other experiments dedicated to new physics searches. Presented here are the physics motivation, experimental setup, potential hadronic effects and their implications, and the future of PV DIS at Jefferson Lab.
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Languages : en
Pages : 180
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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.
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Languages : en
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We use dispersion relations to evaluate the ?Z box contribution to parity-violating electron scattering in the forward limit, taking into account constraints from recent JLab data on electroproduction in the resonance region as well as high energy data from HERA. The correction to the asymmetry is found to be 1.2 +- 0.2% at the kinematics of the JLab Qweak experiment, which is well within the limits required to achieve a 4% measurement of the weak charge of the proton.
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Languages : en
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Measuring the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from protons is a practical technique for determining the contribution of strange quarks to the charge radius and magnetic moment of the nucleon. First results have recently been published by JLab and MIT-Bates.
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Languages : en
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We report on the measurement of parity-violating asymmetries in the deep inelastic scattering and nucleon resonance regions using inclusive scattering of longitudinally polarized electrons from an unpolarized deuterium target. The effective weak couplings C$_{2q}$ are accessible through the deep-inelastic scattering measurements. Here we report a measurement of the parity-violating asymmetry, which yields a determination of 2C$_{2u}$ - C$_{2d}$ with an improved precision of a factor of five relative to the previous result. This result indicates evidence with 95% confidence that the 2C$_{2u}$ - C$_{2d}$ is non-zero. This experiment also provides the first parity-violation data covering the whole resonance region, which provide constraints on nucleon resonance models. Finally, the program to extend these measurements at Jefferson Lab in the 12 GeV era using the Solenoidal Large Intensity Device was also discussed.
Author: Marie-anne Bouchiat
Publisher: World Scientific
ISBN: 9814544086
Category :
Languages : en
Pages : 550
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Book Description
In the last few years there has been considerable progress in improving the accuracy of parity violation experiments in electron scattering at high energy and in atomic physics. Recent results are a challenge to the standard electroweak theory and our understanding of hadron structure. This book is an extensive review of the advances in this field. The theoretical framework is presented at a pedagogical level, experiments and future projects are reviewed, and the results and their interpretation are discussed in depth.
Author: E J Beise
Publisher: World Scientific
ISBN: 9814611506
Category :
Languages : en
Pages : 246
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Book Description
These proceedings cover the recent progress and future directions of parity violation in electron scattering. Both experimental and theoretical issues are discussed, such as those of hadronic structure, radiative corrections, and tests of the standard model. There are three sessions, the first of which serves as a general overview of theory and experiment. The second session deals with the technical aspects of making a measurement of the parity violating asymmetry in electron scattering, including not only detector design but polarized electron beams and beam polarimeters.. The remaining session covers the corrections to lowest order parity violating cross sections.
Author:
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Languages : en
Pages : 15202
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Book Description
Jefferson Laboratory has the potential to make a dramatically improved measurement of parity violation in Moeller scattering (e + e â e + e). In the context of the Standard Model, the measurement would yield the best determination of sin2  W at low energy ( sin2  W = ±0.00025), and one of the best at any energy scale. As a new physics search via the running of the weak mixing angle, the experiment would have unparalleled sensitivity to new parity-violating e? e interactions, probing electron substructure to 29 TeV (95% CL). In terms of specific models, pulls of 6A are allowed in R-parity violating SUSY, about 5A in E6 Z2, and almost 3A in R-parity conserving SUSY. The latter makes an improved Moeller measurement complementary to searches for SUSY loop-induced Electric Dipole Moments. Interpretability limits are well below the projected experimental error. A conceptual design for a 12 GeV JLab experiment is presented.
