A shower containing ∼360 charged and neutral shower particles produced by a magnesium nucleus of 2×1014e.v. provides a source of mesons whose interactions have been studied over an aggregate track length of about 3 meters in emulsion. It is first shown that in very large showers not only the incident energy can be determined but also the energy of the shower particles. The angular distribution of the shower particles agrees closely and their multiplicity is consistent with Fermi’s theory.
It is shown that the interaction cross-section of charged shower particles is geometric and that at an energy ∈ ∼ 1000µc2 they produce on the average 5 to 6 mesons. The mesons are preferentially emitted in the backward direction in the reference system in which the momentum of the incident meson balances that of a nucleon in the target. The excitation produced in the target nucleus is much lower than in nucleon-produced showers of comparable multiplicity.
The charged mesons arenot emitted in pairs by a heavier meson of short lifetime.
Charged shower particles as well as electrons produce electron-positron pairs with a cross-section of the order of that predicted by theory.
The number of neutral mesons decaying intoγ-rays in a time ≤10−14 sec. is nearly equal to the number of charged shower particles.
There exists evidence for the emission of neutral particles, different from neutrons, capable of producing meson showers.
The energy balance of the event suggests that a few shower particles carry an appreciable fraction of the total energy.