The scattering of mesotrons in metal plates

Abstract

Measurements by Blackett and Wilson (1938) showed that the scattering of cosmic-ray particles in metal plates was in approximate agreement with the simple theory then available, at least for energies less than 2 x 10 9 e-volts. This result provided important evidence as to the nature of the cosmic-ray particles, for it tended to confirm the view that the penetrating particles were much heavier than electrons, rather than the alternative assumption that the particles were electrons for which radiative energy losses were suppressed at high energies. Recently, Williams (1939) has given a critical development of the theory of scattering of very energetic particles in the atomic field. This treatment leads to a more accurate value of the theoretical Coulomb scattering and shows that, for cosmic-ray scattering experiments, a fairly sharp separation in angular range is to be expected between scattering in the Coulomb field of the scattering atom and that arising from the short-range interaction between the incident particle and the separate nuclear particles. Accurate measurements of scattering therefore offer a method of estimating the magnitude of the short-range interaction of mesotrons with neutrons or protons. Williams, for example, shows that our previous measurements indicate a mesotron-proton (neutron) interaction decidedly less than that of slow neutrons with protons.