LOW-ENERGY PI+ SCATTERING FROM LIGHT-NUCLEI

Angular distributions for elastic and inelastic scattering of ∼ 50 MeV π+ projectiles from targets of C12, O16, Si, and Fe are reported. Systematic differences between the experimental results and predictions of some first-order theories constructed from free π-N amplitudes are observed for all cases studied. These discrepancies are similar to those reported earlier. Although several improved optical models exist which take into account better treatments of the first-order potential as well as some second-order effects such as π absorption and the Lorentz-Lorentz effect, good agreement with the data cannot be achieved without a phenomenological adjustment of the potential parameters. A purely phenomenological Kisslinger potential when used to fit the data yields potential parameters which are independent of mass number over the A region studied. The resulting p-wave parameter b1 is close to the value predicted from free πN models, while the s-wave parameter b0 requires severe adjustment of both real and imaginary parts from the value predicted from free πN models. The inelastic results are compared to distorted-wave Born-approximation calculations, which are seen to manifest characteristics similar to those seen in the elastic channel. A common optical potential is found to provide a good description of both elastic and inelastic scattering. NUCLEAR REACTIONS Elastic and inelastic scattering of 50 MeV π+ from C12, O16, Si and Fe. Angular distributions: 25°<L<145°. Optical model and DWBA of cross-section data. © 1979 The American Physical Society.