A Measurement of the Weak Charge of the Proton through Parity Violating Electron Scattering using the Qweak Apparatus: A 21% Result

Beminiwattha, R.

doi:10.2172/1079206

Cited by 12 publications

(34 citation statements)

References 36 publications

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“…These data carry information about the location of the electron interaction in the detector volume and the event rates on the detector which can be used to track individual electrons through the setup for the Q 2 measurement. A detailed description of the tracking-mode DAQ layout and triggers can be found in the dissertation of Rakitha Beminiwattha [41].…”

Section: Tracking-mode Daqmentioning

confidence: 99%

“…Table 4.2 shows the event cuts used in the parity analysis engine of QwAnalysis software version 3.04, which was used for the pass-five analysis of the data presented in this dissertation. A lower current cut of 100 µA was required 3 to remove low current beam which were seen [41] to shift theČerenkov detector asymmetries in a non-statistical way. The upper event cut on the BPM wires removes saturation which bounds on theČerenkov detector PMTs, sum of the PMTs (barsum) and background detectors are used as a precautionary measure to remove non-physical signals that can be generated due to hardware failures or software failures 4 .…”

Section: Parity Analysis Enginementioning

confidence: 99%

“…In cooperating all of the above gives the beam normal single spin asymmetry in elastic electron-proton scattering B n = −5.350 ± 0.067 stat ± 0.137 Sys ppm (6.22) for the effective kinematics of acceptance averaged electron energy of E = 1.155 ± 0.003 GeV, Q 2 = 0.0250 ± 0.0006 (GeV/c) 2 and a average scattering angle θ s = 7.9 ± 0.3 0 [41]. Table 6.15 shows the breakdown of corrections applied on the physics asymmetry to extract B n using the above equation.…”

Section: Beam Normal Single Spin Asymmetry From the Protonmentioning

confidence: 99%

“…But the analysis of the commissioning data set (about 4% of the total data set) is complete and will be published in the near future as a proof of concept of the data analysis [167]. The complete analysis of the commissioning data is presented in the dissertation of R. Beminiwattha [41] and was not repeated in this dissertation. However, the results and a discussion will be presented here for completeness.…”

Section: The Determination Of the Weak Charge Of The Protonmentioning

confidence: 99%

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A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

Waidyawansa

2013

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The beam normal single spin asymmetry generated in the scattering of transversely polarized electrons from unpolarized nucleons is an observable of the imaginary part of the two-photon exchange process. Moreover, it is a potential source of false asymmetry in parity violating electron scattering experiments. The Q weak experiment uses parity violating electron scattering to make a direct measurement of the weak charge of the proton. The targeted 4% measurement of the weak charge of the proton probes for parity violating new physics beyond the Standard Model. The beam normal single spin asymmetry at Q weak kinematics is at least three orders of magnitude larger than 5 ppb precision of the parity violating asymmetry. To better understand this parity conserving background, the Q weak Collaboration has performed elastic scattering measurements with fully transversely polarized electron beam on the proton and aluminum. This dissertation presents the analysis of the 3% measurement (1.3% statistical and 2.6% systematic) of beam normal single spin asymmetry in electronproton scattering at a Q 2 of 0.025 (GeV/c) 2 . It is the most precise existing measurement of beam normal single spin asymmetry available at the time. A measurement of this precision helps to improve the theoretical models on beam normal single spin asymmetry and thereby our understanding of the doubly virtual Compton scattering process.

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Section: Tracking-mode Daqmentioning

confidence: 99%

Section: Parity Analysis Enginementioning

confidence: 99%

Section: Beam Normal Single Spin Asymmetry From the Protonmentioning

confidence: 99%

Section: The Determination Of the Weak Charge Of The Protonmentioning

confidence: 99%

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A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

Waidyawansa

2013

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“…During Run 1 the experiment relied primarily on BCM1 & 2, which provided a DD 12 of 100-140 ppm 34 Root-Mean-Square 35 Analog to Digital Converter 36 Double Difference (see Fig. 9).…”

Section: Beam Current Measurementmentioning

confidence: 99%

The Qweak experimental apparatus

Wang¹

2013

AIP Conference Proceedings

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The Jefferson Lab Q weak experiment determined the weak charge of the proton by measuring the parityviolating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ep asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 µA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicitycorrelated beam properties that can induce false asymmetries. Møller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8 • and 11.6 • were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silicaČerenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q 2 = 0.025 GeV 2 was determined using dedicated low-current (∼100 pA) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.

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The Qweak experimental apparatus

Allison

Anderson

Androić

et al. 2015

Nuclear Instruments and Methods in Physics Research Section A:

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The Jefferson Lab Q weak experiment determined the weak charge of the proton by measuring the parityviolating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ep asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 µA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicitycorrelated beam properties that can induce false asymmetries. Møller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The electron beam was incident on a 34.4 cm liquid hydrogen target. After passing through a triple collimator system, scattered electrons between 5.8• and 11.6• were bent in the toroidal magnetic field of a resistive copper-coil magnet. The electrons inside this acceptance were focused onto eight fused silicaČerenkov detectors arrayed symmetrically around the beam axis. A total scattered electron rate of about 7 GHz was incident on the detector array. The detectors were read out in integrating mode by custom-built low-noise pre-amplifiers and 18-bit sampling ADC modules. The momentum transfer Q 2 = 0.025 GeV 2 was determined using dedicated low-current (∼100 pA) measurements with a set of drift chambers before (and a set of drift chambers and trigger scintillation counters after) the toroidal magnet.

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A Measurement of the Weak Charge of the Proton through Parity Violating Electron Scattering using the Qweak Apparatus: A 21% Result

Cited by 12 publications

References 36 publications

A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

A 3% Measurement of the Beam Normal Single Spin Asymmetry in Forward Angle Elastic Electron-Proton Scattering using the Qweak Setup

The Qweak experimental apparatus

The Qweak experimental apparatus

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