Optical Analysis of the 900-MeVπ−−pResonance

Abstract

A model for elastic scattering near the 900-MeV iT-p resonance is proposed, consisting of a Breit-Wigner term together with an optical background. The optical background is chosen to fit experimental data beyond the 900-MeV resonance; the spin of the Breit-Wigner term is then adjusted to give an elastic cross section in agreement with experiment. A distorted-wave Born-approximation calculation shows a spin-f resonance term to be in agreement with the data, in accord with the usual spin assignment. Parity of the Breit-Wigner term cannot be decided from the elastic energy spectra and angular distributions alone; however, if the elastic resonance is identified with the observed K-K resonance near 900 MeV, one finds a suitable branching ratio only for the Z) 5 / 2 choice. The resulting K-K angular distributions, as well as the production cross section as a function of energy, agree generally with experiment. It is therefore proposed that the 900-MeV w~-p resonance has negative parity relative to the proton.

Optical Potential for High-Energy Physics: Theory and Applications

“…From an S-matrix viewpoint, (74) can be adopted as an initial requirement that the eikonal method be applicable. Then 2C can be defined by …”

“…One class of models in which (74) can always be satisfied is the class in which all t dependence of Bornapproximation matrix elements is the same, reflecting a similar radial dependence of the equivalent staticoptical-potential matrix elements. At first thought, these seem to be very restrictive, since elementary oneparticle-exchange potentials give very different ranges for different quantum numbers.…”

“…Purely ad hoc methods of this kind have been used, 74 but there are many possible ways of accomplishing the purpose. It is desired to have some theoretical framework within which to make approximations to ensure consistency.…”