Measurement of the Spin Structure Function GD1 of the Deuteron and Its Moments at Low Q2

<p>Double polarization cross section differences (Δσ ||) for proton and deuteron targets have been measured in the EG4 experiment using the CLAS detector at Jefferson Lab. Longitudinally polarized electron beams at relatively low energies of 1.056, 1.337, 1.989, 2.256 and 3.0 GeV from the CEBAF accelerator were scattered off longitudinally polarized NH₃ and ND₃ targets. Scattered electrons were recorded at very low scattering angles (down to <strong>θ</strong>= 6°) with the help of a new dedicated Cherenkov counter and a special magnetic field setting of the CLAS detector in order to measure the cross section differences in the resonance region (1.08 GeV < <em>W</em> < 2.0 GeV) at very low momentum transfers (<em>Q</em>² for the deuteron was as low as 0.02 GeV²). These measurements on the deuteron were used to extract the deuteron's spin structure function <em>g</em>1 as well as the product <em>A</em>1<em>F</em>1 of the virtual photon asymmetry <em>A</em>1 and the unpolarized structure function <em>F</em>1. These extracted quantities, in turn, were used to evaluate three important integrals for the deuteron - the first moment (Γ 1 of <em>g</em>1, the extended Gerasimov-Drell-Hearn (GDH) integral (<em>ĪTT</em>), and the generalized forward spin polarizability (γ0). These measurements extend and improve the world deuteron data on <em>g</em>1 to the previously unmeasured low <em>Q</em>² region. The data, in combination with the corresponding proton data from the same experiment, will be valuable to extract <em>g</em>1 on the neutron in the same kinematics. They will shed more light on the nucleon spin structure in the region of quark-confinement as well in the transition region between hadronic and partonic degrees of freedom. In addition, the three integrals evaluated from the measured data are compared to predictions from different Chiral Perturbation Theory (χPT) calculations and phenomenological models. Extrapolations of the integrals (especially the GDH sum and the polarizability) to the real photon point (<em>Q</em>²=0) enable us to test the validity of the predictions for their real photon counterparts. The new results have extended and improved the very low <em>Q</em>² data on <em>g</em>1 and the corresponding results on moments compare very well with the latest χPT and phenomenological calculations (especially near the photon point).</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date.available

2013

Author dc:creator

• Adhikari, Krishna P.

Contributors dc:contributor

• Sebastian E. Kuhn
• J. Wallace Van Orden
• Gail E. Dodge
• Leposava Vuskovic
• John A. Adam

• Deuteron spin
• GDH sum rule
• Low Q2
• Nucleon spin
• Spin structure
• Structure function
• Nuclear

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Identifier

9781303774706

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:physics_etds-1020