Investigation of the main characteristics of the superhigh energy primary cosmic radiation in the GAMMA experiment (Mt. Aragats, Armenia)

The all-particle energy spectrum of the Primary Cosmic Radiation obtained from the data of GAMMA array (3200 m a.s.l., 700 g/cm2 of atmospheric depth) is presented. The results are obtained by the event-by-event method of the E0 -energy estimation which is developed using the EAS simulation with use of the software CORSICA and the SIBYLL interaction model with subsequent reconstruction of shower parameters taking into account the response of GAMMA detectors, reconstruction errors, as well as fluctuations of EAS development. By using this method an essential “bump”-shaped irregularity is observed in the all-particle spectrum at primary energies of ∼7.4×107 GeV; the bump exceeds a smooth power-law fit to the data by about 4 standard deviations. From the results of studies of the systematic uncertainties of our methods conclusion is made that the observed irregularity has a physical nature rather than is caused by methodical errors. A model explaining this phenomenon is proposed.