Date of Award
Doctor of Philosophy (PhD)
Electron scattering data from the MIT-Bates linear accelerator were used to derive longitudinal and transverse response functions (S(,L), S(,T)) for the quasi-elastic (QE) kinematic region from uranium targets. Incident energies ranged from 100 to 690 MeV at five laboratory scattering angles: 60, 90, 134.5, 140, and 160 degrees. The Rosenbluth separations using all five angles were obtained at three momentum transfers (q) from 250 to 500 meV/c. Both response functions compared well to relativistic Fermi Gas Model (FGM) predictions at higher values of q, but the S(,L) peak was progressively lower and broader than the FGM at lower q. This difference in responses was reflected in the longitudinal sum rule and in the evaluation of y-scaling. The S(,L) integrated strength was generally about 30% larger than the transverse FGM strength throughout. The S(,L) sum, however, was reduced to about 60% of the model prediction at lower values of q and increased to almost 100% as q increased to 500 MeV/c. No significant quenching in S(,L) was observed at the larger values of q. S(,T) also clearly demonstrated scaling behavior over most of the QE peak for three different y-scaling variables, two non-relativistic and one relativistic. Because of the changing shape of the S(,L) peak with q as compared to the FGM, the S(,L) scaling functions did not appear to be converging to an asymptotic limit for any of the three scaling variables over the range of q tested. This deviation from scaling for S(,L) possibly indicates the presence of some other process. To perform the analysis for this experiment, several innovations over existing techniques were required. Radiative codes were modified to insure validity for large atomic number. In particular, terms which accounted for the emission of a real photon by the recoiling nucleus were added. The full screening approximation was replaced by a formalism which more rigorously included the effects of atomic electrons. This same approach was used to change the calculation of the radiation length used in all the radiative correction codes. A a quasi-elastic phase shift approximation for calculating the effect of Coulomb distortion of the electron wave function was developed. This correction was necessary to preserve the linearity of the Rosenbluth equation and thus allow separations into longitudinal and transverse responses.
Blatchley, Charles Carroll, "Quasi Elastic Electron Scattering in Uranium-238 (Longitudinal, Sum-Rule, Pion, Nuclear, Structure)." (1984). LSU Historical Dissertations and Theses. 4005.