The Scattering of Mesotrons in Tungsten

Abstract

Measurements of the scattering of mesotrons have been made with a 30-cm counter-controlled cloud chamber in a 12,900-oersted magnetic field. The scattering block consisted of 3.8 cm of tungsten, and the lowest Geiger-Mueller counter was mounted directly over the center of the tungsten. Scattering angle and curvature measurements were made on 359 tracks. In addition, there were 92 high energy tracks with a deflection too small to be measurable. The scattering angles varied from 0 to 18.7\ifmmode^\circ\else\textdegree\fi{}, and the mean energies $\overline{E}$ were nearly all less than 2\ifmmode\times\else\texttimes\fi{}${10}^{9}$ ev. The values of the product $\overline{E}\ensuremath{\theta}$ varied from zero to a maximum of 13.7\ifmmode\times\else\texttimes\fi{}${10}^{9}$ ev degrees. These results confirm Williams' prediction of a Gaussian distribution of multiple scattering. A number of cases of anomalous large-angle scattering were obtained, as contrasted with the single case of large-angle scattering observed by Wilson, establishing a departure at these angles from the Gaussian law. This further substantiates Williams' theory with reference to large-angle scattering caused by nuclear forces. The mean value of the multiple electrical scattering calculated from Wilson's equation is 2.2\ifmmode\times\else\texttimes\fi{}${10}^{9}$ ev degrees for this experimental arrangement, which compares with the experimental value of 2.14\ifmmode\times\else\texttimes\fi{}${10}^{9}$. This very satisfactory agreement supports Williams' assumption that the main force responsible for the Gaussian part of the scattering is that arising from the electric charges of the mesotron and of the nucleus.