[PDF] The Precision Measurement Of The Neutron Spin Structure Function Using Polarized He 3 Target eBook

Author : T. Smith
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Page : 205 pages
File Size : 24,74 MB
Release : 2003
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This thesis describes a precision measurement of the neutron spin dependent structure function, g{sub 1}{sup n}(x). The measurement was made by the E154 collaboration at SLAC using a longitudinally polarized, 48.3 GeV electron beam, and a {sup 3}He target polarized by spin exchange with optically pumped rubidium. A target polarization as high as 50% was achieved. The elements of the experiment which pertain to the polarized {sup 3}He target will be described in detail in this thesis. To achieve a precision measurement, it has been necessary to minimize the systematic error from the uncertainty in the target parameters. All of the parameters of the target have been carefully measured, and the most important parameters of the target have been measured using multiple techniques. The polarization of the target was measured using nuclear magnetic resonance techniques, and has been calibrated using both proton NMR and by measuring the shift of the Rb Zeeman resonance frequency due to the {sup 3}He polarization. The fraction of events which originated in the {sup 3}He, as measured by the spectrometers, has been determined using a physical model of the target and the spectrometers. It was also measured during the experiment using a variable pressure {sup 3}He reference cell in place of the polarized {sup 3}He target. The spin dependent structure function g{sub 1}{sup n}(z) was measured in the Bjorken x range of 0.014

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Page : pages
File Size : 33,80 MB
Release : 2001
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In experiment E154 at the Stanford Linear Accelerator Center the spin dependent structure function g[sub 1][sup n] (x, Q[sup 2]) of the neutron was measured by scattering longitudinally polarized 48.3 GeV electrons off a longitudinally polarized[sup 3]He target. The high beam energy allowed the author to extend the kinematic coverage compared to the previous SLAC experiments to 0.014[le] x[le] 0.7 with an average Q[sup 2] of 5 GeV[sup 2]. The author reports the integral of the spin dependent structure function in the measured range to be[integral][sub 0.014][sup 0.7] dx g[sub 1][sup n](x, 5 GeV[sup 2])=[minus]0.036[+-] 0.004(stat.)[+-] 0.005(syst.). The author observes relatively large values of g[sub 1][sup n] at low x that call into question the reliability of data extrapolation to x[r-arrow] 0. Such divergent behavior disagrees with predictions of the conventional Regge theory, but is qualitatively explained by perturbative QCD. The author performs a Next-to-Leading Order perturbative QCD analysis of the world data on the nucleon spin dependent structure functions g[sub 1][sup p] and g[sub 1][sup n] paying careful attention to the experimental and theoretical uncertainties. Using the parameterizations of the helicity-dependent parton distributions obtained in the analysis, the author evolves the data to Q[sup 2]= 5 GeV[sup 2], determines the first moments of the polarized structure functions of the proton and neutron, and finds agreement with the Bjorken sum rule.

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Page : pages
File Size : 19,6 MB
Release : 2009
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Experiment E97-110 was performed at the Thomas Jefferson National Accelerator Facility in Hall A to provide a precise measurement of the moments of the neutron and $^{3}$He spin structure functions. A longitudinally-polarized electron beam was scattered from a longitudinally or transversely polarized $^{3}$He target. The extended Gerasimov-Drell-Hearn integral and other moments of the neutron and $^{3}$He spin structure functions were extracted at very low momentum transfers (0.02 $

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Page : 11 pages
File Size : 28,42 MB
Release : 2004
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Described is a study of the internal spin structure of the neutron performed by measuring the asymmetry in spin-dependent deep inelastic scattering of polarized electrons from nuclear polarized 3He. Stanford Linear Accelerator experiment E142's sample of 400 million scattering events collected at beam energies between 19 and 26 GeV led to the most precise measurement of a nucleon spin structure function to date. The 3He target represents a major advance in polarized target technology, using the technique of spin exchange with optically pumped rubidium vapor to produce a typical 3He nuclear polarization of 34% in a 30cm long target cell with a gas density of 2.3 x 102° cm−3. The target polarization was measured to "7% using an Adiabatic Fast Passage NMR system calibrated with the thermal equilibrium polarization of the protons in a sample of water. The relatively high polarization and target thickness were the result of the development of large volume glass target cells which had inherent nuclear spin relaxation times for the 3He gas of as long as 70 hours. A target cell production procedure is presented which focuses on special glass blowing techniques to minimize surface interactions with the 3He nuclei and careful gas purification and vacuum system procedures to reduce relaxation inducing impurities.