Muon problem in UHECR investigations

Abstract

Abstract. In many UHECR experiments, some excess of muons is observed, which cannot be explained in frame of the existing theoretical models of hadron interaction. Attempts of its explanation through a heavy mass composition of PCR contradict the results of X max measurements. Really, the excess of muons appears already at lower energies (10 16 -10 17 eV), but in this domain it may be explained by the trend to a heavier mass composition, which is in a qualitative agreement with the galactic model of CR origin. The absence of heavy nuclei at energies of the order of 10 18 eV requires to consider other possibilities of the appearance of muon excess, including changes of hadron interaction model. The actuality of the considered problem is connected with plans of future experiments in UHECR physics, in which the necessity of its solution must be taken into account.

Study of the energy deposit of muon bundles in the NEVOD detector

“…This excess may appear due to the changing behavior of hadronic interactions and may indicate the appearance of new physical processes, production of new state of matter in interactions of primary cosmic ray particles with air nuclei, etc. [6].…”