Spin-Rotation Parameters and Phase-Shift Ambiguities inπ−NScattering

Abstract
It is shown that there are three phase-shift ambiguities that can occur when not all possible observables are available for the phase-shift analysis at a given energy in spin-0-spin-½ scattering. Two of the ambiguities, change of sign of the phases and exchange of opposite-parity phases, have been recognized for some time. The third ambiguity, which is the combination of the first two, can be resolved only by measurement of the spin-rotation parameter.