Observations of Cosmic-Ray Events in Nuclear Emulsions Exposed below Ground

Abstract

Ilford Nuclear research plates were manufactured in a laboratory at an equivalent depth of 60 m. of water below ground. After having been stored at various depths, the plates were processed below ground. The observed frequencies of μ-mesons stopped in the plates are consistent with those expected from measurements on the energy-spectrum of cosmic rays. Several π-mesons stopping in the plates were observed, and reasons for believing these to have been locally produced in the matter near the plates are discussed.