Positive photopion production from {sup 12,13}C using tagged photons
Differential cross sections for the reactions {sup 12,13}C({gamma},{pi}{sup +}){sup 12,13}B* have been measured at five angles 35{degrees}, 62{degrees}, 83{degrees}, 110{degrees} and 145{degrees} using the tagged photons at the mean incident energy 191 MeV. The motivation of the present work was to study the strong spin-isospin excitation modes in the A = 12, 13 nuclei up to 20 MeV excitation energy and compare the structural similarity of the neighboring {sup 12}C and {sup 13}C. The present data overcame the difficulty of the previous continuous photon experiments in extracting the cross sections for the higher excited states and extended the area of the tagged photon measurement by detecting the higher energy pions. The data were taken at Saskatchewan Accelerator Laboratory by impinging the tagged photon beam on graphite {sup 12}C and enriched (99%) {sup 13}C targets. Auxiliary measurement on p({gamma},{pi}{sup +})n was also performed to calibrate detector systems. Positive photopions were detected by a system of plastic scintillator {Delta}E-E telescopes with the thicknesses of 1/8 inches for {Delta}E and 2.5 inches for E detectors. The maximum pion energy system was 42 MeV and the corresponding momentum transfer to the nucleus was ranged 0.5 to 1.5 fm{sup {minus}1}. The strong spin-isospin excitations were observed at 0, 4.5, 7.5, and 10 MeV in {sup 12}B and 0, 3.5, 6.4, 9.5, and 13 MeV in {sup 13}B, which were consistent with the observations by other nuclear reaction probes, the radiative pion capture and the inelastic electron scattering. Differential cross sections for the transitions leading to the observed states were extracted and compared with the available previous measurements and DWIA calculations. A comparison of the cross sections from {sup 12}C and {sup 13}C shows strong similarity in the reaction mechanism in both nuclei.
- Research Organization:
- Rensselaer Polytechnic Inst., Troy, NY (United States)
- OSTI ID:
- 98652
- Resource Relation:
- Other Information: TH: Thesis (Ph.D.); PBD: 1993
- Country of Publication:
- United States
- Language:
- English
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