Nuclear Disintegrations Induced byμ-Mesons

The absorption curve in water of the cosmic radiation producing nuclear disintegrations was obtained by recording the neutron showers occurring in an absorber surrounded by BF₃ counters. It was found that, while the N-component of the cosmic radiation is responsible for most of the disintegrations observed under the first few meters of water, μ-mesons are the particles causing either directly or indirectly most of the events recorded at depths greater than {~}10 m water. The cross section of μ-mesons for nuclear interactions is found to be {~}1×{}10^-29 cm²/nucleon at a depth of 20 m water. Estimates of the absolute intensity of the N-component and of the relative contribution to nuclear disintegrations by μ-mesons and N-component at sea level are given.