Measurement of the fifth structure function in quasi-elastic proton knock-out from carbon
Mandeville, Joseph Bernard
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https://hdl.handle.net/2142/20035
Description
Title
Measurement of the fifth structure function in quasi-elastic proton knock-out from carbon
Author(s)
Mandeville, Joseph Bernard
Issue Date
1993
Doctoral Committee Chair(s)
Papanicolas, Costas N.
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Nuclear
Language
eng
Abstract
This thesis reports the first measurement of the 'fifth structure function' in coincident electron scattering. This new observable breaks the symmetry for detecting nuclear decay products above and below the electron scattering plane when the incident electrons are longitudinally polarized. 560 MeV polarized electrons were scattered from a $\sp{12}$C target, and electrons were detected in the ELSSY spectrometer in coincidence with quasi-elastic knock-out protons, which were detected in the new Out Of Plane Spectrometer (OOPS). We measured polarization asymmetries and total cross sections at a momentum transfer of 1.8 $fm\sp{-1}$ and at two proton angles out of the electron scattering plane and directly above the momentum transfer vector. This $\sp{12}$C($\vec e,e\sp\prime p$) measurement, together with another measurement on deuterium in identical kinematics, was performed at the Bates Linear Accelerator Center in Middleton, MA, in July, 1991.
These fifth structure function measurements inaugurate the out-of-plane program at Bates laboratory. In order to isolate the interference structure functions which arise in coincident scattering using polarized incident electrons, we have advocated simultaneous measurements using identical detectors positioned on a cone at $\pi$/2 intervals around the momentum transfer vector. We have designed a prototype out-of-plane spectrometer as a precursor to a four-spectrometer system, constructed this 15-ton device, demonstrated that the OOPS matches our design goals, and performed the first measurements of a new observable.
"The fifth structure function arises from the interference between two or more reaction amplitudes with different phases. At quasi-elastic kinematics, this quantity is primarily sensitive to the interference between the dominant knock-out amplitude and knock-out followed by nucleon rescattering with the residual nucleus. With only two points and a somewhat limited statistical precision, this measurement does not sufficiently constrain competing models of final state interactions. However, we emphasize the accuracy that is attainable with this method, and we discuss the importance of fifth structure function measurements in the context of the separation of all the interference structure functions. We expect that imminent accelerator and detector developments will lead to dramatic improvements in the ""ease"" and statistical precision of these measurements in the near future."
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