The Mass of Cosmic-Ray Mesotrons

Abstract

By cloud-chamber observations of the curvature of mesotrons in a magnetic field of 4750 gauss and the subsequent range of these same particles in a second cloud chamber containing fifteen lead plates each 0.67 cm in thickness, the mass of 43 cosmic-ray particles has been determined. 37 of these particles appear to give a set of observations that are consistent with a unique mass of 215±4 times the mass of an electron. Of the 6 remaining observations 4 indicate a mass much too large (474, 538, 588, and 717) to be reasonably considered as statistical fluctuations in the observations of normal mesotrons. The remaining 2 observations (114 and 120) also appear to be inconsistent with the normal mass of the mesotron and the observed probable errors in individual measurements in this experiment.