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DOCTORAL THESIS - Michael H. Wood
Low Energy Proton-Deuteron Elastic Scattering and the "Ay
Puzzle"
Doctoral thesis by Michael H. Wood
University of North Carolina at Chapel Hill, 2000
Abstract
Angular distributions of cross sections and complete sets of analyzing
powers have been measured for d-p scattering at a center-of-mass
energy of 667 +/- 1 keV. This set of high-precision data was
compared to the most recent variational calculations with the
nucleon-nucleon potential AV18 alone and with AV18 plus the UR three-nucleon
potential. The calculations have the best agreement with
the cross-section data while the comparison with the tensor analyzing
powers showed good agreement. However, a comparison between the vector
analyzing powers revealed differences of approximately 40% in the
maxima of the angular distributions. These VAP discrepancies have
been observed at Ec.m. > 2.0 MeV as well as in the n-d
scattering case. After the n-d experiments, the problem has been
labelled the ``Ay Puzzle''. A reduced chi-squared analysis was
performed with the lowest values achieved by the inclusion of a
three-nucleon force in the theoretical calculations. This fact
provides more credence for the existence of three-nucleon
forces. However, the reduced chi-squared for the VAPs remained
approximately 100. To investigate the root of the problem in addition
to other differences between the theory and the data, a single-energy
phase shift analysis (PSA) was performed. The best fits to the VAP
data displayed an ~20% increase in the the mixing parameter
epsilon3/2 and an increase in the splitting between
4PJ phase shifts from the variational calculations with
the AV18+UR potentials.
Here you can download the final version of my
thesis, complete with figures: gzipped postscript (427 kb)
The pertinent results in my thesis can be found in:
- Low-energy p-d scattering: High-precision data, comparisons with theory, and phase-shift analyses,
- M. H. Wood, C. R. Brune, B. M. Fisher, H. J. Karwowski, D. S. Leonard, E. J. Ludwig, A. Kievsky, S. Rosati, and M. Viviani, Phys. Rev. C 65, 034002, 8 pages (2002).
Mail:mikewood@jlab.org
Last updated February 10, 2002.