Evidence for the Radioactivity of Slow Mesotrons

Abstract

A beam of mesotrons is selected by means of a fourfold coincidence system of counters, and is allowed to pass through a block of iron 10 cm thick. The absorption of mesotrons by the iron is recorded by means of a battery of anticoincidence counters. It is found that a certain fraction of the stopped mesotrons is associated with the emission of an ionizing particle from the absorber. A special coincidence recording system, whose resolving time is of the order of one microsecond, enables one to establish that the emission of the particles is delayed with respect to the passage of the mesotron by a few microseconds. The delayed particles are interpreted as the electrons resulting from the $\beta$-decay of the mesotron. The present experiment establishes only the order of magnitude of the mean life of the mesotron at rest, but more quantitative measurements are in progress.