γ-ray bundles at the cores of extensive air showers and primary cosmic ray identification

We present a useful clue to estimate the energy and chemical composition of the primary cosmic radiation between ${10}^{14}$ and ${10}^{17}$ eV. The method uses various kinds of quantities as measured by a hybrid detector, an emulsion chamber in the central part of an extensive air shower (EAS) array at mountain altitude. The characteristic features needed for the analysis are derived in detail through the Monte Carlo method. The procedure permits an analysis on individual events; it gives an estimation of the mass and energy of a primary nucleus initiating a shower. The estimation of the primary energy is with quite negligible ambiguity. We show that the EAS size measurement could be complementary to quantities as measured by an emulsion chamber detector to improve the accuracy of the primary cosmic ray identification.