Measurement of low-energy elastic. pi. /sup + -/p differential cross sections

We have measured differential cross sections for both ..pi../sup +/p and ..pi../sup -/p elastic scattering at incident-pion kinetic energies of 30, 50, 70, and 90 MeV in the center-of-mass angular range between 50/sup 0/ and 150/sup 0/. The experiment detected pions scattered from a liquid-hydrogen target with multiwire proportional chambers and scintillation-counter range telescopes. The relative accuracy of each angular distribution is better than 5%, while the absolute cross sections have uncertainties of 4% to 25%. Our results for the absolute cross section for ..pi../sup +/p scattering at 30 and 90 MeV are inconsistent with previous measurements. Our ..pi../sup -/p measurements comprise the first extensive set of precision differential cross sections below 90 MeV.