Measurement of fifth structure function in deuterium
Dolfini, Stephen M.
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Permalink
https://hdl.handle.net/2142/28662
Description
Title
Measurement of fifth structure function in deuterium
Author(s)
Dolfini, Stephen M.
Issue Date
1994
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
deuterium
fifth structure function
out-of-plane spectrometer
Language
en
Abstract
We report the first measurement of f'01, the so called 5th structure function, in deuterium. In conjunction with deuterium, this structure function was measured under identical kinematics in carbon. These measurements constitute the first ever observations of these novel structure functions and the inauguration of the newly developed
Out-Of-Plane Spectrometer (OOPS). The observation of fb1 requires longitudinally
polarized electron beams and out-of-plane detection. This structure function is directly related to the imaginary part of the interference between the transverse and
longitudinal nuclear electromagnetic currents. As a consequence fb1 vanishes identically if only a single amplitude contributes to the observed reaction channel. In our experiment the two dominant amplitudes that interfere, giving rise to f'01, are the ones due to the direct knock-out and rescattering processes. The 2H(e,e'p)n experiment reported here was conducted at the MIT /Bates Linear Accelerator Center in July, 1991. An important part of this work was to develop the methodology for out-of-plane physics as well as design, construct and test the dedicated spectrometer system to optimally perform out-of-plane measurements in the Bates environment. The OOPS weighs 16 tons and is quite slender. It has a momentum resolution of 0.45%, a momentum acceptance of 10%, and a solid angle of 1.2 msr. It is well suited to access a wide range of out-of-plane angles and is capable of performing high precision coincidence measurements on the nucleon and few body systems. We used a 560 MeV polarized electron beam. The measurement took place in the North Hall using the Energy Loss Spectrometer System (ELSSY) as the electron
spectrometer. It was placed at an angle of 40° and the energy transfer, w, was set for
quasi-elastic kinematics with the square of the four-momentum transfer, Q2, equal to - 3.3 fm-2• The angle of the momentum transfer vector, i/, was 60°. The OOPS was placed at out-of-plane angles of 0°, 21° and 29°, corresponding to a >pq angle of 90°. In this kinematic region, the response of the deuteron has been explored before and is rather well understood: contributions to the cross section from processes such as meson exchange currents (MEC) and isobar configurations (IC) are minimal and f~1 is particularly sensitive to final state interactions (FSI). We demonstrated the viability of the OOPS as an optimized instrument for out-of-plane spectrometry and have thus ushered in a new tool for electron scattering. We measured the fifth structure function and the related asymmetry in the coincidence cross section, albeit with large statistical errors, and have shown them to be in agreement with the theoretical predictions of Arenhovel.
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