Cascade Showers and Mesotron-Produced Secondaries in Lead

Abstract

A study has been made of cascade showers in lead and also of electron secondaries accompanying mesotrons in lead. The cloud chamber that was used for the observations contained four lead plates and was placed in an 1100-gauss magnetic field. In the case of showers, comparison with theory was made in terms of: (a) the average shower curve for 11 showers with initiating energies of about 200 Mev; (b) the energy distribution near the shower maximum of 17 showers; (c) the ratio of height to area of the shower curve of 44 showers; and (d) the fluctuation in number of particles in the showers of (a). The theory agrees with the experiment for (b) and (d) but not for (a) and (c). It is likely that errors arising from known physical approximations in the theory account for the discrepancies. In the case of electron secondaries accompanying mesotrons, a study was made of the number of electrons with energy greater than E relative to the number of mesotrons. For small values of $E$, the theoretical values are too large by a factor of two, but as $E$ increases the discrepancy becomes smaller.