Systematic features of the pionnucleus interaction
Abstract
We analyze pion elasticscattering data for ^{40}Ca and ^{48}Ca using a covariant theory of the optical potential developed previously. Combining these results with the information obtained from the analysis of pion scattering from ^{12}C and ^{16}O reported earlier, we are able to discuss the systematics of the pionnucleus optical potential. Our model contains a firstorder optical potential which is obtained from a parameterfree calculation. The parameters of a secondorder potential are determined by requiring that the sum of the firstand secondorder potentials provides a fit to the elasticscattering data. The parameters of the secondorder potential exhibit a smooth dependence on energy and target mass number. These parameters have a marked resonance behavior. We find that the maximum value of the magnitude of the imaginary part of the secondorder potential occurs at about 150 MeV while the firstorder potential has a maximum for the magnitude of the imaginary part at about 240 MeV. The imaginary part of the firstorder potential has a width at half maximum of about 200 MeV. This corresponds to a kinematic broadening of the (3,3) resonance due to the effects of the Fermi motion of the target nucleons. (This increased width is unrelated to the effects of the true absorption process or of collision broadening.) We also find a significant isospin violation in the secondorder potential. For example, the imaginary part of the secondorder potential for π^{} scattering is found to be systematically larger than that for π^{+} scattering for nuclei with N=Z. An explanation for this feature of the optical potential is presented. NUCLEAR REACTIONS Elastic scattering of pions from ^{40}Ca (40241 MeV) and ^{48}Ca (130 MeV). Systematics of first and secondorder optical potentials.
 Publication:

Physical Review C
 Pub Date:
 May 1980
 DOI:
 10.1103/PhysRevC.21.1903
 Bibcode:
 1980PhRvC..21.1903B