Low energyπ+scattering from light nuclei

Abstract

Angular distributions for elastic and inelastic scattering of approx. 50 MeV ..pi../sup +/ projectiles from targets of /sup 12/C, /sup 16/O, Si, and Fe are reported. Systematic differences between the experimental results and predictions of some first-order theories constructed from free ..pi..-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 ..pi.. 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 b/sub 1/ is close to the value predicted from free ..pi..N models, while the s-wave parameter b/sub 0/ requires severe adjustment of both real and imaginary parts from the value predicted from free ..pi..N 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 goodmore » description of both elastic and inelastic scattering.« less