A null technique for calibrating polarization values in $\pi p$ scattering

The purpose of this investigation is to find regions of energy and angle for pi p elastic scattering in which the proton polarization P reaches its maximum value of unity. For incident pion beam energies below 900 MeV, five such regions exist in pi /sup +/p and six such regions exist in pi /sup -/p, as shown by simple graphical techniques. This suggests that crude polarized target experiments measuring the Wolfenstein parameters R and A will precisely determine the proton polarization because of the quadratic relation P/sup 2/+R/sup 2/+A/sup 2/=1. (6 refs).