A Diffusion Cloud-Chamber Study of Pion Interactions in Hydrogen and Helium

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Abstract
A description is given of the operation of a high pressure diffusion cloud chamber filled with hydrogen or helium and exposed to pion beams of both signs and energies near 60 and 100 Mev. Interactions occurring in the gas filling are investigated. The cross sections found in hydrogen agree with the results of others, including the large difference between the cross sections for positive and negative mesons. In helium the total cross sections are 89±18 and 207±27 mb with beams at 60 and 105 Mev, respectively. These cross sections include elastic and inelastic scattering, charge exchange, and absorption. The charge exchange cross sections, estimated at 20 and 60 mb for the two respective energies, are much larger than observed by others for different nuclei. Assuming that the mesons interact with the individual nucleons in the nucleus, an approximate calculation shows that a fairly consistent picture can be obtained making use of phase shifts determined by Anderson et al. for meson scattering on hydrogen.