Longitudinal development of extensive air showers

Abstract

A theory of cosmic ray showers is presented which embraces the following features: it is assumed that the primary radiation consists of nucleons; the nucleons generate the pion component by collision with nuclei; the charged pions decay into muons; the neutral pions decay into photons which initiate the soft component. Detailed numerical results are given for the average numbers (or intensities) of the various components at different dephts in the atmosphere and for different energy ranges (only particles with energies > 10 GreV are considered in this paper). The theory predicts that the charged pion and soft components have maxima at about 125 gm/cm2 and that the number of (high energy) muons increases with depth, showing no maximum. The radiation is predominantly muons up to about 8000 metres and the number of high energy charged pions at sea level is much greater than the number of high energy nucleons. This latter feature provides a test of the assumption that the high energy pions do not interact with nuclei in the atmosphere. It is concluded that high energy charged pions must interact with nuclei and that their interaction mean free path is longer than that for nucleons. Thetotal meson component and the total radiation follow very closely a power law with the same exponent as that assumed for the primary nucleons.