Abstract
As the features of the high energy soft components of cosmic rays have not yet been thoroughly investigated, it is of greet interest to study them at present day, especially in very high energy region (above BeV). To obtain the energy of such high energy electron or photon, the electromagnetic shower theory can be applied.
Using an experimental arrangement consisting of GM-counter hodoscopes and an ionization chamber with large area, the pulse height distribution of cosmic-ray showers produced by electrons or photons in lead and iron absorbers of different thickness was measured. The number of shower particles was estimated from the pulse height considering the angular spread of shower particles, and the energy of electrons or photons was obtained from the results of shower theory. The results of the present experiment show that, i) the differential energy spectra can be represented by a power law of the form E−γ, with γ of 2.90 and 2.80 for electrons and photons of 2–20 BeV, respectively, ii) the zenith angle distribution of electrons is expressed by cos2θ, and iii) upper limit of the ratio of the number of electrons to that of photons is 1.1. It is also found that the calculated results by Ivanenko are favorable to explain the observed results for lead and iron absorbers. The essential part of this investigation is to provide a classification of the incident electrons or photons by the GM-counter hodoscopes, that is, single incident particles, multiple incident ones, and those associated with EAS are separated in order to minimize the ambiguity involved in the results.
