Date Awarded


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Degree Name

Doctor of Philosophy (Ph.D.)




Keith A Griffioen


The Barely off-Shell Nucleon Structure (BoNuS) experiment measured electron scattering from neutrons bound in deuterium nuclei at Jefferson Lab's Hall B with the intent of obtaining the ratio Fn2/Fp2 at high Bjorken x. The Fn2 structure function is difficult to obtain due to nature's lack of a free neutron target. Previous experiments have measured inclusive scattering from atomic nuclei, but extracting Fn2 from these data requires knowledge of inclusive scattering from the proton and corrections for nucleon binding and Fermi motion. In BoNuS we restrict our analysis to neutron scattering events tagged by a backward-going low-energy recoil proton. This selects loosely bound neutrons that are nearly on their mass-shell and have few final state interactions with the recoil proton. The recoil protons were detected in a Radial Time Projection Chamber (RTPC) using gas electron multipliers (GEMs) in a cylindrical geometry around the target. The production data were taken at three beam energies: 2.140 GeV, 4.223 GeV and 5.262 GeV with an additional set of calibration data taken at 1.099 GeV. The kinematic coverage includes the invariant mass, W, from the quasi-elastic peak up to 3.0 GeV and momentum transfer, Q 2, from 0.2 GeV2 up to approximately 3.0 GeV 2. The final experimental observations presented here are the tagged/untagged cross section ratios, corrected for a number of physical processes and backgrounds. The ratio enables us to ignore many complications arising from a typical absolute cross section measurement. An extraction of Fn2/Fp2 for x up to 0.75 is made and compared with previous data These data are important because they can provide a model independent measurement of neutron structure.



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