The Production of High Energy Secondaries by Cosmic Rays Underground

Abstract

The traversal of a total of 100 meters of lead by penetrating particles has been studied at an underground depth of 8.4\ifmmode\times\else\texttimes\fi{}${10}^{4}$ g ${\mathrm{cm}}^{\ensuremath{-}2}$ with a cloud chamber containing 2.54-cm lead plates. The observed probability for an energy transfer greater than ${10}^{9}$ ev to the soft component is 3.0(\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ per g ${\mathrm{cm}}^{\ensuremath{-}2}$ of lead. Knock-on, bremsstrahlung, and pair-production processes are calculated to give a probability of 2.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ per g ${\mathrm{cm}}^{\ensuremath{-}2}$ of lead. Therefore, the above electromagnetic phenomena account for nearly all of the high energy soft secondaries produced by $\ensuremath{\mu}$-mesons of energy \ensuremath{\sim}${10}^{11}$ ev.