Pion elastic and inelastic scattering from Mg24 and Mg26

G. S. Blanpied, J. Hernandez, C. S. Mishra, W. K. Mize, C. S. Whisnant, Barry Ritchie, C. L. Morris, S. J. Seestrom-Morris, C. Fred Moore, P. A. Seidl, R. A. Lindgren, B. H. Wildenthal, R. Gilman

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Abstract

Reported are measurements of angular distributions of resonance-energy positive and negative pions exciting approximately 40 states in Mg24 and Mg26. These include the (ground state, 0+), (1.36 MeV, 2+), (4.14, 2+), (5.93, 4+), (6.44, 0+), (7.34), (7.55, 3-), (8.33, 3-), (9.32, 4+), (9.97, 5-), (11.08, 3-), (12.06), (13.26), (13.96, 3-), (15.1, T=1, 6-), and (15.4) states in Mg24 and the (ground state, 0+), (1.81, 2+), (2.92, 2+), (3.59, 0+), (4.31, 2++4+), (4.90, 4+), (5.31, 2+), (5.44, 4+), (5.69, 4+), (6.86, 3-), (7.33, 3-), (7.79, 3-), (8.17, 3-), (9.2, possible 6-), (10.30, 4+), and (18.1, T=2, 6-) states in Mg26. The distorted-wave impulse approximation with a Kisslinger form for the optical potential using a -nucleon t matrix at a shifted energy of -25 MeV was found to explain the elastic scattering data from Mg24,26 in the energy range 116-292 MeV that is spanned by these data. Inelastic distorted-wave impulse approximation calculations employing collective-model deformation parameters were simultaneously fitted to the + and - data for each state. The deformation parameters and matrix elements in most cases compare favorably with results from other studies. Published s-d shell-model calculations using one value for the effective charges were found to reproduce the trend of both the strengths and ratios of neutron-to-proton matrix elements for the 2+ and 4+ states. The data at the first maximum in the inelastic angular distributions for Mg24 and that from other studies for C12, Si28, and Ca40 show that the cross section for + scattering is equal to that for - scattering, which forces the proton deformation parameters to be greater than the neutron deformation parameters and gives a ratio of neutron-to-proton elements to be less than unity. This difference from unity is interpreted as a measure of the failure of the model and a systematic error of 11% is assumed to dominate the errors in the results for Mg26. Coupled-channels calculations employing monopole form factors are compared to data for low-lying 0+ states in Mg24 and Mg26.

Original languageEnglish (US)
Pages (from-to)1625-1636
Number of pages12
JournalPhysical Review C
Volume41
Issue number4
DOIs
StatePublished - Jan 1 1990

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ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Blanpied, G. S., Hernandez, J., Mishra, C. S., Mize, W. K., Whisnant, C. S., Ritchie, B., Morris, C. L., Seestrom-Morris, S. J., Moore, C. F., Seidl, P. A., Lindgren, R. A., Wildenthal, B. H., & Gilman, R. (1990). Pion elastic and inelastic scattering from Mg24 and Mg26. Physical Review C, 41(4), 1625-1636. https://doi.org/10.1103/PhysRevC.41.1625