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

Magee, J. A.

doi:10.2172/1323226

Cited by 5 publications

(10 citation statements)

References 66 publications

(146 reference statements)

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“…The analysis procedure to extract beam polarization from the Møller measurements is described in Ref. [8,9] while the procedure for the Compton measurements is described in Ref. [6].…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

“…The details of the JLab Hall-C Møller polarimeter are described in Ref. [8,9] larimeter was designed to continuously monitor the beam polarization at high beam currents with better than 1% statistical uncertainty per hour. It consists of four identical dipole magnets forming a magnetic chicane that displaces a 1.16 GeV electron beam vertically downward by 57 cm.…”

Section: Introductionmentioning

confidence: 99%

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A novel comparison of Møller and Compton electron-beam polarimeters

et al. 2017

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We have performed a novel comparison between electron-beam polarimeters based on Møller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents (< 5 µA) during the Q weak experiment in Hall C at Jefferson Lab. These low current measurements were bracketed by the regular high current (180 µA) operation of the Compton polarimeter. All measurements were found to be consistent within experimental uncertainties of 1% or less, demonstrating that electron polarization does not depend significantly on the beam current. This result lends confidence to the common practice of applying Møller measurements made at low beam currents to physics experiments performed at higher beam currents. The agreement between two polarimetry techniques based on independent physical processes sets an important benchmark for future precision asymmetry measurements that require sub-1% precision in polarimetry.

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“…The analysis procedure to extract beam polarization from the Møller measurements is described in Ref. [8,9] while the procedure for the Compton measurements is described in Ref. [6].…”

Section: Data Analysis and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel comparison of Møller and Compton electron-beam polarimeters

et al. 2017

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“…The thin (0.1-mm) entrance and exit windows of the hydrogen target cell were made of aluminum 7075 alloy, which contributed ∼2.5% to the signal. The asymmetry in scattering from this alloy was measured in dedicated runs with a thick solid target made of the same material as the windows (11)(12)(13). Beamline-background asymmetry correction (A BB ).…”

Section: Determination Of a Epmentioning

confidence: 99%

Determination of the Proton's Weak Charge and Its Constraints on the Standard Model

Carlini

Oers

Pitt

et al. 2019

Annu. Rev. Nucl. Part. Sci.

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This article discusses some of the history of parity-violation experiments that culminated in the Qweak experiment, which provided the first determination of the proton's weak charge [Formula: see text]. The guiding principles necessary to the success of that experiment are outlined, followed by a brief description of the Qweak experiment. Several consistent methods used to determine [Formula: see text] from the asymmetry measured in the Qweak experiment are explained in detail. The weak mixing angle sin2θw determined from [Formula: see text] is compared with results from other experiments. A description of the procedure for using the [Formula: see text] result on the proton to set TeV-scale limits for new parity-violating semileptonic physics beyond the Standard Model (BSM) is presented. By also considering atomic parity-violation results on cesium, the article shows how this result can be generalized to set limits on BSM physics, which couples to any combination of valence quark flavors. Finally, the discovery space available to future weak-charge measurements is explored.

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“…for Run 1 and A 1 = 1.515 ± 0.077 ppm (total) for Run 2. Combined with the background fractions determined from evacuated target measurements [98], a total correction of f 1 A 1 = 37 ± 2 ppb (Run 1) and f 1 A 1 = 38 ± 2 ppb (Run 2) were used in the Q weak asymmetry analysis.…”

mentioning

confidence: 99%

“…Examples of acceptable, borderline, and bad IHWP transition runlets can be see in the dissertation by J. A. Magee[98] and Q weak electronic log book (ELOG) entry[123].…”

mentioning

confidence: 99%

First Measurements of the Parity-Violating and Beam-Normal Single-Spin Asymmetries in Elastic Electron-Aluminum Scattering

Author¹

2018

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The Q weak collaboration has made the first measurements of the elastic parity-violating and beam-normal single-spin asymmetries from the Al 27 nucleus. Both are the result of ancillary measurements conducted during the Q weak experiment at Jefferson Lab. The goal of the experimental was to determine the proton's weak charge, Q p W , via a measurement of the elastic parity-violating electron-proton scattering asymmetry. During the experiment, ancillary measurements were made with different beam configurations on a separate aluminum alloy target, in an effort to directly measure the aluminum background coming from the experiment's liquid hydrogen target cell. This dissertation discusses three primary results: the parity-violating Al 27 asymmetry analysis used to correct for the aluminum target background in the final Q weak analysis, its extended analysis leading to the extraction of the pure elastic parity-violating Al 27 asymmetry, and the determination of the elastic beam-normal single-spin Al 27 asymmetry. The parity-violating result was also used to make a semi model-independent determination of Al 27 neutron distribution radius, an important test for models used to describe neutron-rich matter. The beam-normal single-spin asymmetry stands to possibly shed light on an observed disagreement between theory and a previous measurement performed on Pb 208 , as Al 27 is the next highest atomic mass nucleus to have this observable measured. The elastic parity-violating Al 27 asymmetry was found to be 1.927 ± 0.173 ppm at Q 2 = 0.0236 ± 0.0001 GeV 2. This measured parity-violating asymmetry implies a Al 27 neutron distribution radius of 3.024 ± 0.104 fm. Calculating the difference between this radius and the Al 27 proton distribution radius yields the neutron skin, which was found to be 0.092 ± 0.104 fm. This skin value is consistent with zero, within its uncertainty, and it confirms the naive expectation for a light nucleus like Al 27. The beam-normal single-spin Al 27 asymmetry was found to be −16.322 ± 2.679 ppm at Q = 0.154 GeV. This value agrees with the previous observed trend of beam-normal single-spin asymmetries measured from light nuclei, which motivates the need for future measurements of higher atomic mass nuclei.

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

Cited by 5 publications

References 66 publications

A novel comparison of Møller and Compton electron-beam polarimeters

A novel comparison of Møller and Compton electron-beam polarimeters

Determination of the Proton's Weak Charge and Its Constraints on the Standard Model

First Measurements of the Parity-Violating and Beam-Normal Single-Spin Asymmetries in Elastic Electron-Aluminum Scattering

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