Muons in EAS with E>=10^17eV according to the data from Yakutsk array

Abstract

The lateral distribution of muons with threshold energy e ~ 1*sec(theta) GeV have been studied in showers with energy E>=10^17 eV. The data considered in the analysis have been collected from November 2011 to June 2013. Experimental values are compared to predictions obtained with the use of CORSIKA code within the framework of various hadron interaction models. The best agreement between experiment and theory is observed for QGSJETII-04 model. At E~10^17 eV it complies to a mixed cosmic ray composition with the mean atomic number <lnA>~3.0+/-0.5. At E>= 4*10^17 eV the composition varies around the value <lnA>~0.5.