On the electrical and anomalous scattering of mesotrons

Abstract

Photographs obtained without a magnetic field in a large counter-controlled cloud chamber containing lead plates of two different thicknesses have been analyzed in regard to the scattering of the mesotrons in lead. The theory of scattering developed by E. J. Williams has been used. The mathematical form of this theory makes it possible to eliminate the energy distribution of the mesotrons in comparing the observed scattering intensity in two lead thicknesses. The scattering in a 5-cm lead plate into angles greater than 4\ifmmode^\circ\else\textdegree\fi{}, when compared to that in a 1-cm lead plate, is more than would have been expected on the basis of Williams' theory. The average cross section calculated for this anomalous large angle scattering agrees with the results obtained by Code but it is somewhat larger than that previously reported by Wilson. It is also noted that this cross section is in agreement with the interaction between mesotrons and nuclei computed by Marshak and Weisskopf when a spin of \textonehalf{} for the mesotrons and an energy distribution such as that computed by Hartree are assumed. Although these experiments are perhaps not yet able to distinguish between the scatterings to be expected from a mesotron spin of \textonehalf{} and that from a spin of 0, a spin of 1 seems to be definitely excluded since for this value of the spin the theory indicates a cross section of about 1000 times more than that found. It is noted that a possibility for an explanation of the observed anomaly still might be found in electromagnetic effects such as those leading to burst production by mesotrons or in attributing the anomaly to nuclear scattering of the proton component instead of mesotrons.