Phenomenological Transition Amplitudes: Consequences for Pion and Eta Photoproduction in 1PSHELL Nuclei.
Abstract
Recent theoretical calculations for pion photoproduction for transitions in 1pshell nuclei often rely on nuclear transition density matrix elements extracted from low energy electromagnetic and weak observables. I determine "windows of reliability" of nuclear structure input these calculations by extracting the onebody densities as a function of momentum transfer from electromagnetic and weak observables. At high momentum transfer (q > 3fm ^{1}, for example), harmonic oscillator singleparticle wavefunctions decay too rapidly. Radial wavefunctions obtained by using the HartreeFock method or generated from the WoodSaxon well can improve the fit to the electroweak observables at momentum transfers where the harmonic oscillator wavefunctions become inadequate. I examined possible mesonexchange current effects, from which pion photoproduction appears to be immune. I confront pion photoproduction measurements to assess the differences between the theoretical predictions of my amplitudes and the amplitudes of other works. I demonstrate that nuclear photoproduction with polarized photons can be particularly sensitive to model ingredients, such as nuclear structure and the impulse amplitude. I exploit this sensitivity using the photon asymmetry, which is a measure of the nuclear response to the different photon polarizations. Finally, I study eta photoproduction to investigate the roles of the S_{11}(1535) resonance, vector mesons, and the sand u channel nucleon Born terms. The pure M1 1pshell transitions studied in this thesis are: ^6Li_{rm g.s.} to ^6 Li*(3.56MeV), ^{12}C _{rm g.s.} to ^{12}C*(15.11MeV), and ^{14}N_ {rm g.s.} to ^{14}N*(2.313MeV). These transitions are of interest to the experimental studies at various photon factories around the world.
 Publication:

Ph.D. Thesis
 Pub Date:
 1989
 Bibcode:
 1989PhDT........66D
 Keywords:

 Physics: Nuclear