Secondary spectra of electrons and photons in the atmosphere

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Abstract
Electrons and photons of the secondary cosmic radiation have been separated from the other components by means of their shower development in a lead scintillator arrangement. Measurements have been performed at 4.5 GV geomagnetic cutoff at atmospheric depths of 760 g/cm2 (in vertical direction between 12 MeV and 20 GeV, inclined at 36 °N between 12 MeV and 1 GeV, and inclined at 49° and 59 °N between 70 MeV and 1 GeV) and 955 g/cm2 (in vertical direction between 12 MeV and 1 GeV). The results can be characterized as follows.1. For the energy range covered at both locations and/or at different zenith angles there is no significant change in the spectral shape.2. Both the photon and the electron spectra steepen gradually, the exponent of the differential power-law spectrum E−n assuming a value n = 2.8 for energies above 1 GeV.3. The photon/electron ratio is in good agreement with the ratio of the track-length distributions calculated by Richards and Nordheim for electromagnetic cascades in air.4. A cosnθ law is a poor approximation to the angular distribution of the integral intensities above 100 MeV. A better fit is obtained from calculations taking into account the relative contributions of π0's and muons to the electron and photon intensities at a given zenith angle θ.