Transition effect of air shower particles in the thin absorder

Abstract

The response of plastic scintillators to the flux of particles in extensive air showers of various sizes was measured at various distances from the core. One scintillator was placed above the other, and thin iron absorber was inserted between them, varying its thickness. The ratio of the particle density measured by the lower scintillator ϱlower to that measured by the upper one ϱupper, ϱlower/ϱupper, was found to decrease with the core distance and to be almost independent of the shower size. In case of iron absorber of 1 mm thickness, the ratio was found to be ∼1.2 forr≤1.5 m, and decrease to ∼1.0 forr≥10 m, wherer is the distance from the core. The empirical formulae for the transition effect were obtained. Modification of shower parameters due to the transition effect was investigated, using these formulae. A theoretical estimate of the transition effect was carried out, and it was shown that the observed transition effect could be explained by the cascade of the electromagnetic components of air shower within the scintillator and absorber.