New technique and results of cosmic ray investigations in the energy interval 1015–1019 eV

New technique of EAS investigations based on the measurements of local muon density spectra (LMDS) is developed. Application of this method to investigations of inclined EAS allows exploration of CR energy interval from 10(15) to 10(19) eV by means of a relatively small detector with area similar to 100 m(2) due to very strong dependence of EAS muon density on zenith angle. During 2002-2007, long-term NEVOD-DECOR experiment (about 20,000 h live time) was conducted, and more than two million muon bundles in zenith angle interval 30-88 degrees were registered. Comparison of experimental data with results of CORSIKA-based simulations showed that the new method is sensitive to all main peculiarities of CR energy spectrum: the knee, increase of the energy spectrum slope with energy, the second knee. But the observed progressive excess of muon bundles with the increase of primary CR energy in comparison with simulations (even for pure iron composition) can indicate the appearance of new processes of muon generation. In this case, for correct investigations of EAS, the experimental arrays must be supplemented by detectors which can measure or evaluate the energy of muons.