Theory of inelastic lepton-nucleus scattering

Yen, Granddon
Major Professor
James P. Vary
Committee Member
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Physics and Astronomy
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Physics and Astronomy

This work reports the studies of the quark structure of a nucleus. Deuterium is the simplest nuclear system with weak binding energy and low average density so that it provides an ideal starting point for this study. Models based on the one photon exchange process should provide a good description of deuterium inelastic lepton scattering data. Furthermore, the available deuterium data cover the widest kinematical range among all A ≥ 2 targets. If the conventional nuclear physics picture is correct, the quasi-elastic nucleon knockout process along with nucleon inelastic processes should be able to account for the inelastic lepton scattering data. However, there are uncertainties in the deuteron wavefunctions, nucleon elastic form factors and nucleon inelastic structure functions. To understand these uncertainties and their possible role in obscuring the quark structure of the nucleus, I examined two deuteron wavefunction models: Reid Soft Core (RSC) and Bonn; three nucleon elastic form factors: Blatnik and Zovko, Hohler, and Gari and Krumpelmann; and three nucleon inelastic structure function models: Buras and Gaemers (BG), Abbott, Atwood and Barnett (AAB), and Duke and Owens (DO). The Gari and Krumpelmann nucleon form factors combining the meson dynamics at low Q[superscript]2 and QCD quark dynamics at high Q[superscript]2 should perform better in the long run, and are turned to fit available nucleon data. On the other hand the nucleon inelastic structure functions are not free of ambiguities. While the AAB and DO seem to fit data better in the higher Q[superscript]2 region, I chose BG in my deuterium calculations because it fits the nucleon inelastic data better in the kinematic region (2.5 ≤ Q[superscript]2 ≤ 8 GeV[superscript]2) where the deuterium data are analyzed. The Bonn potential is based on a more sophisticated meson exchange theory, and is believed to more accurately describe a wider spectrum of nuclear properties. The theoretical results with the RSC wavefunction agree with data fairly well, while the Bonn wavefunction opens the door to the 6-quark cluster to play an important role. With the Bonn deuterium wavefunctions I determined that the critical radius for 6-quark cluster formation R[subscript]C ~ 0.49 fm which provides a 5% probability of a 6-q cluster configuration in the ground state of deuterium.