The elastic scattering of 80-Mev ${\pi }^{-}$ mesons by lithium, carbon, aluminum, and copper has been investigated using a ${\pi }^{-}$ detector which gives improved discrimination against low-energy-loss inelastic events. A "transmission" scatterer orientation was necessary to maintain energy resolution, so only less than 120° scattering was studied. The new differential scattering cross sections for lithium, aluminum, and copper agree with the previously reported results at small angles but are 2 to 10 times smaller at larger angles. There are indications of diffraction structure in aluminum and copper which were not previously observed due to the poorer energy resolution of the earlier measurements.

Including the incident beam energy spread, the detector sensitivity is down by factors of 3 and 9 for $E\pm 5.0$ Mev and $E\pm 10$ Mev when peaked for mean energy $E$. This was used to separate the scattering from carbon into elastic and inelastic components for excitation of the 4.43 and (7.65 and 9.61) Mev levels. Inelastic scatterings from lithium have also been studied. For the same momentum transfer on scattering, the ratio of the inelastic scattering with excitation to the 4.43-Mev and 9.61-Mev levels to the elastic differential scattering cross section is the same, within experimental accuracy, as found by Fregeau for the scattering of 187-Mev electrons on carbon. The elastic scattering is compared with the results of complex square-well phase shift calculations, and with diffuse-edge optical model and modified Kisslinger model calculations.

• Received 4 August 1958

DOI:https://doi.org/10.1103/PhysRev.112.1763