The charge-exchange scattering of negative pions by protons at 96.6 MeV

The angular distribution of γ rays from the charge-exchange scattering of 96.6 MeV negative pions by protons has been measured at 14 angles between 20° and 151.2°. The γ-ray detector utilized a lead converter and counter telescope. The correction for loss of electrons in the converter was determined experimentally and the calculated efficiency of the detector checked by direct measurement with a tagged beam of γ rays. Analysis of the distribution of γ rays yielded the following differential cross section for the charge-exchange scattering (mbn sterad-1 c.m.): dσ/dΩ=(0.694 ± 0.047) - (1.56 ± 0.05) cosθ + (1.89 ± 0.14) cos2θ Using previously determined values for the T = 3/2 phase shifts, those for the T = ½ state were found to be α1 = 8.28 ± 0.56°; α11 = -5.0 ± 1.1°; α13 = -0.23 ± 0.47°.