Accurate measurement of the electron beam polarization in JLab Hall A using Compton polarimetry

Escoffier, S.; Bertin, P.Y.; Brossard, Michel; Burtin, E.; Cavata, C.; Colombel, N.; Jager, C. W. de; Delbart, A.; Lhuillier, D.; Marie, F.; Mitchell, J.; Neyret, D.; Pussieux, T.

doi:10.1016/j.nima.2005.05.067

Cited by 28 publications

(25 citation statements)

References 9 publications

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“…Displayed numbers are not corrected for the laser polarization, Pγ = 99.5%. As an extra cross-check, an online photon analysis [15] was also performed ( P e P γ = 84.64 ± 0.1 ± 2.1%, not displayed here) as well as one Møller measurement in the middle of the run (green triangle). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)…”

Section: Polarimetrymentioning

confidence: 99%

Strangeness in the nucleon: Newest results from Happex and G0

Lhuillier

2008

Progress in Particle and Nuclear Physics

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Section: Polarimetrymentioning

confidence: 99%

Strangeness in the nucleon: Newest results from Happex and G0

Lhuillier

2008

Progress in Particle and Nuclear Physics

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“…11 for Compton, background and noise events 12 Red and blue histograms in top two panels show the counts for positive and negative helicity …”

Section: Detector Orientationmentioning

confidence: 99%

“…If one assumes a Gaussian intensity prole for these two beams, the luminosity is also a Gaussian function of the distance between the two beam centroids [12]. Since the optical axis of the cavity gets mechanically fixed by the mirror holder, the position variation of We assume that the four beam parameters, the x-position, y-position, θ x and θ y are uncorrelated.…”

Section: Beam Position At Interaction Pointmentioning

confidence: 99%

Determination of electron beam polarization using electron detector in Compton polarimeter with less than 1% statistical and systematic uncertainty

Narayan¹

2015

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Title of Study: Determination of electron beam polarization using electron detector inCompton polarimeter with less than 1% statistical and systematic uncertainty Pages of Study: 250Candidate for Degree of Doctor of PhilosophyThe Q-weak experiment aims to measure the weak charge of proton with a precision of 4.2%. The proposed precision on weak charge required a 2.5% measurement of the parity violating asymmetry in elastic electron -proton scattering. Polarimetry was the largest experimental contribution to this uncertainty and a new Compton polarimeter was installed in Hall C at Jefferson Lab to make the goal achievable.In this polarimeter the electron beam collides with green laser light in a low gain FabryPerot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in lead tungstate crystals. This diamond micro-strip detector is the first such device to be used as a tracking detector in a nuclear and particle physics experiment. The diamond detectors are read out using custom built electronic modules that include a preamplifier, a pulse shaping amplifier and a discriminator for each detector micro-strip. We use field programmable gate array based general purpose logic modules for event selection and histogramming. Extensive Monte Carlo simulations and data acquisition simulations were performed to estimate the systematic uncertainties. Additionally, the Moller and Compton polarimeters were cross calibrated at low electron beam currents using a series of interleaved measurements. In this dissertation, we describe all the subsystems of the Compton polarimeter with emphasis on the electron detector. We focus on the FPGA based data acquisition system built by the author and the data analysis methods implemented by the author. The simulations of the data acquisition and the polarimeter that helped rigorously establish the systematic uncertainties of the polarimeter are also elaborated, resulting in the first sub 1% measurement of low energy (∼1 GeV) electron beam polarization with a Compton electron detector. We have demonstrated that diamond based micro-strip detectors can be used for tracking in a high radiation environment and it has enabled us to achieve the desired precision in the measurement of the electron beam polarization which in turn has allowed the most precise determination of the weak charge of the proton.

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“…Each CPU card handed off control of the crate at the end of its helicity window. [221] During E06-014, we commissioned a second data acquisition system, based on a modified 12-bit FADC from Struck DE, running with a sampling rate of 200 MHz. The timing of the readout commands is based on a HAPPEX Timing Board [222] that provides start-acquisition, stop-acquisition, and readout commands based on the master pulse signal (MPS), which marks a brief period of Figure 4.13: A wiring diagram for the newly commissioned integrating data acquisition system for Compton photon data.…”

Section: Data Acquisitionmentioning

confidence: 99%

Measurements of the Double-Spin Asymmetry A<sub>1</sub> on Helium-3: Toward a Precise Measurement of the Neutron A<sub>1</sub>

Parno

2011

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The spin structure of protons and neutrons has been an open question for nearly twenty-five years, after surprising experimental results disproved the simple model in which valence quarks were responsible for nearly 100% of the nucleon spin. Diverse theoretical approaches have been brought to bear on the problem, but a shortage of precise data -especially on neutron spin structure -has prevented a thorough understanding.Experiment E06-014, conducted in Hall A of Jefferson Laboratory in 2009, presented an opportunity to add to the world data set for the neutron in the poorly covered valence-quark region. Jefferson Laboratory's highly polarized electron beam, combined with Hall A's facilities for a high-density, highly polarized 3 He target, allowed a high-luminosity double-polarized experiment, while the large acceptance of the BigBite spectrometer gave coverage over a wide kinematic range: 0.15 < x < 0.95. In this work, we present the analysis of a portion of the E06-014 data, measured with an incident beam energy of 4.74 GeV and spanning 1.5 < Q 2 < 5.5 (GeV/c) 2 . From these data, we extract the longitudinal asymmetry in virtual photon-nucleon scattering, A 1 , on the 3 He nucleus. Combined with the remaining E06-014 data, this will form the basis of a measurement of the neutron asymmetry A n 1 that will extend the kinematic range of the data available to test models of spin-dependent parton distributions in the nucleon. AcknowledgmentsNo one in this age can earn a physics PhD based solely on her own work and study; the making of a doctor, like the making of a modern particle-physics experiment, requires the goodwill and support of many. In my own life and studies, I have been profoundly blessed by the presence of my family, friends, and colleagues. It is traditional to thank these wonderful people in these pages, as though words were enough. They aren't, but they are a start.My parents, Christine Marwick and Richard Seymour, brought me up to have both a deep curiosity about the world and the work ethic I needed to answer my own questions. The love of language my mother gave me made writing this dissertation far less painful than it might have been; my father urged me to take my first voluntary science course and then kindly refrained from saying "I told you so" at the sudden fascination with physics that resulted. My not-so-little brother, Matthew, kept me honest with everything I did.The love and support of my extended family has been invaluable. My grandparents, Bob and Dolores Marwick, generously funded my undergraduate education. They and my aunts, uncles, and assorted cousins, scattered around the continent, taught me that I could find something of home wherever I am. To Rob and Ann Marwick, Mike and Monica Marwick, Lorrie Marwick and Guy Marsh, Nancy and Don DeMuth, and Josephine Marwick, thank you for the delicious meals, the fascinating conversations and your willingness to talk physics. To my beloved cousins, thank you for everything. Growing up, I was also lucky to enjoy the love of many peo...

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Accurate measurement of the electron beam polarization in JLab Hall A using Compton polarimetry

Cited by 28 publications

References 9 publications

Strangeness in the nucleon: Newest results from Happex and G0

Strangeness in the nucleon: Newest results from Happex and G0

Determination of electron beam polarization using electron detector in Compton polarimeter with less than 1% statistical and systematic uncertainty

Measurements of the Double-Spin Asymmetry A<sub>1</sub> on Helium-3: Toward a Precise Measurement of the Neutron A<sub>1</sub>

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