Phase-Shift Analysis of Elastic Pion-Nucleon Scattering

Abstract

A many-energy analysis of pion-nucleon scattering data in the energy range 20-340 MeV has been carried out by fitting phase shifts in $S$, $P$, $D$, and $F$ states in gradient searches. Semiphenomenological analyses, with $F$-wave phase shifts calculated from approximate evaluations of pion-nucleon dispersion relations and $D$-wave phase shifts similarly obtained for the lower energy range, have been equally successful in fitting the data. Particular attention has been paid to the possibility of obtaining a unique set from all possible sets allowed by data. Several sets of phase shifts have been found. One of these, called SEMI IIM, is preferred by data and by comparison with dispersion-theoretical calculations. Comparisons with other recent analyses are made.